CMB Week 3&4 Flashcards
Transport epithelia
forms a single layer of cells and function to move solutes and water across cell membranes and from one compartment to another
Epithelia has polarity, which means
there are two distinct sides that carry out distinct functions. These are the apical and basalolateral
The apical side of epithelia faces the
lumen (inside or middle) of the organ
The basolateral side of epithelia faces
the intercellular solution and the bloodstream
Paracellular transport is
movement of water and solutes through tight junctions between epithelial cells
Transcellular transport
movement of water and solutes through epithelial cells
Usually the basolateral membrane has a high density of … pump molecules which maintain a large transmembrane ….
Usually the basolateral membrane has a high density of Na+/K+ pump molecules which maintain a large transmembrane gradient of Na+
microvilli
small finger-like extensions that project into a lumen and possess a core of actin filaments
stereocilia
non-motile microvilli which may be branched
Cilia
- hair-like projections of the apical cell surface - much larger than microvilli - motile structures containing a microtubule core, the axoneme - function, mainly to move substances across the surface of an epithelial layer
basal bodies
cilia are anchored via basal bodies, which are comprised of nine micro tubular triplets
Primary ciliary dyskenia
immotile cilia syndrome
Kartagener’s syndrome
- cilia lack dynein arms - leads to chronic respiratory distress due to lack of mucous transport - male sterility due to immotile sperm
Young’s syndrome
- cilia have malformed radial spokes and dynein arms - unusually thick mucous secretions - persistent sinusitis - reduced male fertility or sterility
What type of proteins are found in zonula occludens?
occludin, claudins, and cadherins
What type of proteins are found in zonula adherens?
cadherins, catenins
What type of proteins are found in desmosomes?
desmoplakins and pakoglobins (forms attachment plaques)
Connexons
- found at gap junctions - formed from integral membrane proteins called connexins
Clostridium perfringens are pathogens that
- produces a toxin that binds to claudin proteins - junctions breakdown - symptoms include diarrhea and abdominal pain
Heliobacter pylori is a pathogen that
- binds to extracellular domains of zonula occludins proteins - cytoskeletal rearrangements and junction failure results - leads to gastric ulcers
Dust mites are parasitic pathogens:
- fecal pellets contain peptidases that cleave occludin - inhalation of fecal pellets - tight junctions in the respiratory epithelium breakdown, leads to asthma attacks
Hemidesmosomes
- attach the basal cell membrane to the basal lamina - mediated by integral membrane proteins called integrins
The basement membrane includes
the two layers of the basal lamina and a third layer, lamina reticularis
Exocrine glands secrete their products …
via a duct or duct system
Endocrine glands
- are not connected to the epithelial surface - are ductless and secrete their products into blood or lymphatic vessels
Goblet cells are
unicellular glands
Multicelluar exocrine glands are classified by two criteria:
- complexity of their duct system - morphology of their secretory portions
Simple duct systems have
one duct and can be straight, branched or coiled
Compound duct systems are
complex, branched, differentiated duct systems
In general, compound glands are … that have a …., are divided into …
In general, compound glands are organs that have a connective tissue capsule, are divided into lobes and lobules.
Parenchyma
the ducts and secretory portions of compound glands
stroma
the tissue components which surround and support the parenchymal tissue
two types of secretory cells
- mucous - secretes mucinogens (large glycosylate proteins) - serous - secrete solution of proteins
Myoepithelial cells
- epithelial derived cells surrounding the basal aspect of secretory cells - have contractile filaments and their contraction aids in moving secretions out of the secretory portion of the glands
catabolism
- break down of molecules - usually exergonic - releases energy
anabolism
- assembly of complex molecules - usually endergonic - needs energy
ΔG
- change in free energy - energy available to do work - predicts if a reaction is favorable - equals 0 at equilibrium - Negative ΔG - proceeds to equilibrium, is exergonic reaction - Positive ΔG - will not occur independently, endergonic reaction
Glycolysis is the only energy-generating reaction that is an
anaerobic process
Glycolysis occurs in the
cytosol
How many ATP molecules generated from glycolysis?
2 ATPs
What are the energy generating reactions in mitochondria?
- pyruvate dehydrogenase complex (PDH) - fatty acid beta-oxidation - Krebs cycle - terminal oxidation (Electron transport and Oxidative phosphorylation)
The malate-aspartate and the alpha-glycerol shuttles transfer
The malate-aspartate and the alpha-glycerol phosphate shuttles transfer reducing equivalents from the cytosol to the mitochondrial matrix.
Beta oxidation is the ….
Beta oxidation is the oxidative degradation of fatty acids to harvest the energy from them to turn to ATP.
What are the sources for pyruvate?
glucose and certain AAs
Under aerobic conditions, pyruvate is converted to
AcCoA
Under anaerobic conditions, pyruvate is
reduced to lactate
The pyruvate dehydrogenase (PDH) complex turns pyruvate to
AcCoA
The reaction of the PDH complex
2 Pyruvate + 2 (NAD+) + 2 CoA → 2 acetyl-CoA + 2 CO2 + 2 NADH + 2H+
The ΔG for the PDH complex reaction is … and highly …. This reaction is ….
The ΔG for the PDH complex reaction is negative and highly favorable. This reaction is irreversible.
What are the three enzymes contained in the PDH complex?
E1: pyruvate dehydrogenase E2: dihydrolipoyl transacelytase E3: dihydrolipoyl dehydrogenase
Name the five coenzymes contained in the PDH complex
Tender Loving Care For Nancy Thiamine Pyrophosphate (TPP, B1) Lipoid Acid (a vitamin) Coenzyme A (Vitamin B5) FAD (Vitamin B2) NAD (Vitamin B3)
Name the regulatory enzymes contained in the PDH complex
Protein kinase, phosphoprotein phosphatase
The first step in the PDH complex
Pyruvate is decarboxylated to form a hydroxyethyl derivative bound to TPP. E1 catalyzes this reaction, and this is the rate limiting step.
What is the coenzyme (cofactor) for pyruvate dehydrogenase (E1)?
TPP (thiamine pyrophosphate)
What are the coenzymes for dihydrolipoyl transacelytase (E2)?
lipoic acid and coenzyme A
What are the coenzymes for dihydrolipoyl dehydrogenase (E3)?
FAD (B2) and NAD (B3)
The second step in the PDH complex
Hydroxyethyl intermediate transferred to lipoic acid, which is bound to E2.
The third step in the PDH complex
Acetyl group (bounded to lipoic acid) is transferred to CoA.
The fourth step in the PDH complex
E3 and FAD catalyze reaction to regenerate lipoic acid, producing FADH2 in the process
The fifth step in the PDH complex
E3 and the NAD cofactor oxidizes FADH2 back to FAD, reducing NAD to NADH in the process
ATP, Acetyl CoA, and NADH are positive regulators of the PDH complex, meaning they …
ATP, Acetyl CoA, and NADH are positive regulators of the PDH complex, meaning they inhibit the reaction when enough of these products are present.
In the presence of the products from the PDH complex, protein kinase …
In the presence of the products from the PDH complex, protein kinase inactivates PDH by phosphorylation.
Pyruvate, when available, inhibits …. The PDH complex can now be activated by
Pyruvate, when available, inhibits protein kinase. The PDH complex can now be activated by phosphatase, through dephosphorylation.
PDH complex deficiency is
is a genetic mitochondrial disease where there is deficiency in pyruvate metabolism, either in the catalytic or regulatory subunits of the PDH complex. Most common cause of congenital lactic acidosis.
Lactic acidosis can arise from either
can arise from either a deficiency in the PDH complex or decreased O2 delivery to tissues, leading to inhibition of the PDH complex and an increase in anaerobic metabolism.
Patients suffering from lactic acidosis can be treated with …, which inhibits …, thereby … the PDH complex.
Patients suffering from lactic acidosis can be treated with dichloroacetate, which inhibits kinase, thereby activating the PDH complex.
Patients suffering from congenital lactic acidosis are sometimes put on what type of diet?
Patients suffering from congenital lactic acidosis are sometimes put on a ketogenic diet, which is a high fat, adequate protein, and low carbohydrate diet.
Sources of Acetyl CoA
- pyruvate (PDH complex) - β-oxidation of fatty acids - some amino acids
Different paths (uses) of Acetyl CoA
- complete oxidation in the tricarboxylic acid cycle (TCA) for energy production - Conversion of excess AcCoA to ketone bodies in the liver - Biosynthesis of sterols and long chain fatty acids in the cytosol
Krebs Cycle (TCA): Key enzymes (emphasized from lecture)
Key enzymes - Citrate synthase - Isocitrate dehydrogenase - α-Ketoglutarate dehydrogenase - Succinyl CoA synthase - Succinate dehydrogenase - Malate dehydrogenase
Each turn of the TCA cycle creates
3 NADH molecules, 1 FADH2, and 1 GTP (1 ATP)
During Krebs cylce, GTP is converted to
one ATP molecule
The regulation of the TCA cycle is largely determined by …. and ….
The regulation of the TCA cycle is largely determined by product inhibition and substrate availability.
Arsenic poisoning inhibits enzymes that use …. as a cofactor, such as … and ….
Arsenic poisoning inhibits enzymes that use lipoic acid as a cofactor, such as dihydrolipoyl transacelytase and α-Ketoglutarate dehydrogenase.
Fumarase deficiency:
Fumarase deficiency is an autosomal recessive disorder that results in severe neurological impairment, encephalomyopathy, and dystonia (abnormal muscle tone).
The intermediates of the TCA cycle can be used to
synthesize biomolecules, including fatty acids, steroids, glucose, heme, neurotransmitters, and several AAs.
Pyruvate carboxylase can replenish the intermediates of the TCA cycle by converting … to …. Another source for replenishing TCA intermediates are ….
Pyruvate carboxylase can replenish the intermediates of the TCA cycle by converting pyruvate to oxaloacetate. Another source for replenishing TCA intermediates are amino acids.
What is electron transport?
Electron carries transport electrons and protons from reduced coenzymes NADH and FADH2 to oxygen. Energy released from this is then converted to ATP.
Components of the electron transport chain
- 4 large multi-unit enzyme complexes with redox systems (Complex I-IV) - Coenzyme Q - Cytochrome C
The Electron Transport Chain (steps)
- NADH enters the system at Complex I, which transfers electrons and protons to Coenzyme Q - FADH2 enters the system at Complex II, which transfers electrons and protons to Coenzyme Q. (Complex II is succinate dehydrogenase) - Coenzyme Q also accepts FADH2 from beta-oxidation of fatty acids. - Electrons are transferred to Complex III - Complex III transfers electrons to cytochrome C - cytochrome C transfers electrons to Complex IV - Complex IV transfers electrons to molecular oxygen
The fish poison, …, and the barbiturate … inhibits complex I.
The fish poison, rotenone, and the barbiturate amytal inhibits complex I.
In the electron transport chain, during the removal of the electrons, protons are:
In the electron transport chain, during the removal of the electrons, protons are also removed and pumped across the inner membrane to the inter-membrane space, creating an electrochemical gradient that provides energy for ATP synthesis.
The antibiotic …. inhibits complex III.
The antibiotic antimycin A inhibits complex III.
…., …., and …. inhibits the terminal step at complex IV.
Cyanide, azide, and carbon monoxide inhibits the terminal step at complex IV.
Cyanide: mechanism of action at Complex IV
- inhibits the terminal step by binding to the Fe3+ ion at heme a3 of cytochrome C oxidase enzyme - this prevents oxygen from binding to the enzyme - mitochondrion respiration and energy production ceases, and cell death results
Treatment for cyanide poisoning
- administration of various nitrites that convert oxyhemoglobin to methemoglobin (oxidation of Fe2+ to Fe3+) - Methemoglobin competes with cytochrome a3 for cyanide, creating a methemoglobin-cyanide complex.
The protons (generated from electron transport chain) in the inter-membrane space of the mitochondria are then transported back into the …. by ….
The protons (generated from electron transport chain) in the inter-membrane space of the mitochondria are then transported back into the mitochondrial matrix by F1F0-ATPase (located in the inner membrane).
The F0 portion of F1F0-ATPase makes the membrane… F0 subunit is sensitive to …. (an antibiotic).
The F0 portion of F1F0-ATPase makes the membrane permeable to protons. F0 subunit is sensitive to oligomycin (an antibiotic).
The F1 portion of F1F0-ATPase contains the … enzyme and … occurs on the surface of F1.
The F1 portion of F1F0-ATPase contains the ATPase enzyme and synthesis of ATP occurs on the surface of F1.
2,4-dinitrophenol is an example of an uncoupler, which are molecules that ….
2,4-dinitrophenol is an example of an uncoupler, which are molecules that can dissipate the proton gradient from electron transport chain and cause rapid oxygen consumption. Electron transport continues without ATP synthesis.
Thermogenin or Uncoupling Protein 1 (UCP-1) is found in …. UCP-1 promotes ….
Thermogenin or Uncoupling Protein 1 (UCP-1) is found in mitochondria of brown adipose tissue. UCP-1 promotes heat production by transporting protons back into the mitochondrial matrix, diverting energy from ATP synthesis to heat production.
Leber’s Hereditary Optic Neuropathy (LHON) is a ….. LHON results from a single ….
Leber’s Hereditary Optic Neuropathy is a mitochondrial disease that affects the central nervous system. LHON results from a single base change in the mitochondrial genes for three subunits of complex I.
LHON patients with lower percentage of the mutant mtDNA develop
sudden onset blindness in early adulthood.
LHON patients with higher percentage of the mutant mtDNA develop
dystonia, impaired speech, and mental retardation.
Mitochondrial myopathies are due to point mutations in genes encoding for …, resulting in ….
Mitochondrial myopathies are due to point mutations in genes encoding for mitochondrial tRNA, resulting in impaired mitochondrial protein synthesis, leading to decreased activities of complex I and complex IV.
Mitochondrial diseases are characterized by …, ….(mitochondrial encephalomyopathy).
Mitochondrial diseases are characterized by abnormalities of the CNS, mitochondrial myopathy with ragged red muscle fibers (mitochondrial encephalomyopathy).
A mutation in …. results in lowered activity of complex III (electron transport chain), and is characterized by ….
A mutation in cytochrome b results in lowered activity of complex III (electron transport chain), and is characterized by exercise intolerance.
Metastasis
the spread of a cancer or other disease from one organ or part to another not directly connected with it
Angiogenesis
the physiological process through which new blood vessels form from pre-existing vessels
Tumor cells consume high levels of glucose, and are not responsive to … or …
Tumor cells consume high levels of glucose, and are not responsive to insulin or glucagon.
The source of glucose for tumor cells is the ….. Tumor cells get AAs from ….
The source of glucose for tumor cells is the blood. Tumor cells get AAs from skeletal muscle.
Cancer cachexia (unexplained weight loss) can be caused by:
- Decreased appetite and food intake 2. increased energy need of the cancer cells 3. secretion of factors that stimulate skeletal muscle and fat tissue wasting 4. endocrine imbalance - insulin resistance, higher than normal cortisol level, higher basal metabolic rate.
Endocrine systems employ chemical messengers (hormones) that are …
Endocrine systems employ chemical messengers (hormones) that are released and diffuse into the blood for distribution throughout the body.
Paracrine systems employ hormones that
diffuse short distances to affect neighboring cells.
Autocrine systems employ a hormone to
influence its own behavior
Neuroendocrine and synaptic chemical messenger systems release
Neuroendocrine and synaptic chemical messenger systems release neurotransmitters that diffuse very short distances to a specific neighboring cell that affects its behavior.
Juxtacrine signaling involves cell-cell contact and can happen in two ways:
- a molecule in the membrane of one cell interacting with a molecule on a target cell 2. connexin molecules forming a gap junction between two adjacent cells through which small molecules (typically ions) can diffuse
A hormone that has trophic effects on another endocrine gland, promotes
the gland’s health, but does not necessarily directly stimulate the release of a hormone.
Proteins, peptides, and glycoproteins have a very low solubility in …. and higher solubility in ….
Proteins, peptides, and glycoproteins have a very low solubility in lipids and higher solubility in water.
Steroids are very insoluble in …. and are soluble in ….
Steroids are very insoluble in water and are soluble in lipids.
Amines such as epinephrine and norepinephrine are … soluble but insoluble in …
Amines such as epinephrine and norepinephrine are water soluble but insoluble in lipids.
Endocrine responses take … while neural responses are within ….
Endocrine responses take minutes to hours or days while neural responses are within milliseconds to minutes.
Chemical messengers are removed from the circulation by the
liver and kidneys
A neuro-endocrine system (Adrenal medulla) is one in which neural activity in the ….. stimulates the release of a … that enters the circulation to produce widespread systemic effects.
A neuro-endocrine system (Adrenal medulla) is one in which neural activity in the pre-ganglionic sympathetic fiber stimulates the release of a hormone that enters the circulation to produce widespread systemic effects.
Features of Fragile X Syndrome (FXS)
- Physical: large prominent ears, long face, large head, prominent jaw and forehead, midfacial hypoplasia (lower than normal development of tissue or organ), hyper flexible joints, large testis - Intellectual Disability or learning disability - behavior problems (hyperactivity, distractibility, anxiety, perseveration, aggression) - autism - seizures - strabismus (abnormal alignment of the eyes) - medical (otitis, sinus, reflux, sleep apnea)
FXS is associated with a rare fragile site at location …. on the … and is caused by a mutation in the ….. gene.
FXS is associated with a rare fragile site at location Xq27.3 on the X-chromosome and is caused by a mutation in the fragile X mental retardation-1 (FMR1) gene.
Features of Fragile X Syndrome (FXS)
- Physical: large prominent ears, long face, large head, prominent jaw and forehead - Intellectual Disability or learning disability - behavior problems (hyperactivity, distractibility, anxiety, perseveration, aggression) - autism - seizures - strabismus (abnormal alignment of the eyes) - medical (otitis, sinus, reflux, sleep apnea)
FXS is associated with a rare fragile site at location …. on the …
FXS is associated with a rare fragile site at location Xq27.3 on the X-chromosome.
Typically, the CGG repeat on the FMR-1 gene ranges from
6 to 44 repeats
The full mutation of the FMR-1 gene has a repeat expansion
greater than 200 repeats, with subsequent hypermethylation of the CpG island (transcriptionally inactive).
About …% of males and …% of females who have the FMR-1 gene full mutation have ….
About 95% of males and 50% of females who have the FMR-1 gene full mutation have intellectual disability.
In the premutation of the FMR-1 gene, the copy number repeat ranges from ….. The premutation is not …, and is transcriptionally ….
In the premutation of the FMR-1 gene, the copy number repeat ranges from 55-200. The premutation is not methylated, and is transcriptionally active.
Individuals with the premutation of FMR-1 gene are at risk for
developing fragile X-associated tremor/ataxia syndrome (FXTAS) and fragile X associated primary ovarian insufficiency (FXPOI)
Gray zone allele in FMR-1 gene are … repeats. These alleles are not enough to cause disease but may be risk factors for … like Parkinson’s.
Gray zone allele in FMR-1 gene are 45-54 repeats. These alleles are not enough to cause disease but may be risk factors for late onset neurodegenerative diseases like Parkinson’s.
The FMR-1 protein (FMRP) is an RNA binding protein that is a …. Absence of FMRP results in:
The FMR-1 protein (FMRP) is an RNA binding protein that is a negative modulator of dendritic translation. Absence of FMRP results in abnormal excessive protein synthesis in dendritic connection leading to abnormal brain development.
Gray zone allele in FMR-1 gene are … repeats. These alleles are not enough to cause disease but may be risk factors for …
Gray zone allele in FMR-1 gene are 45-54 repeats. These alleles are not enough to cause disease but may be risk factors for late onset neurodegenerative diseases like Parkinson’s.
Clinically normal males who carry a premutation (of FMR-1 gene) are termed … b/c they transmit the premutation to their …, and subsequent grandchildren get the …
Clinically normal males who carry a premutation (of FMR-1 gene) are termed transmitting males b/c they transmit the premutation to their daughters, and subsequent grandchildren get the full mutation.
Sherman paradox
the large variation in the recurrence risk for intellectual disability in FXS cannot be fully explained by classic Mendelian genetics and is termed the Sherman paradox, which is explained by DNA instability or dynamic mutations.
Clinically normal males who carry a premutation (of FMR-1 gene) will:
Clinically normal males who carry a premutation (of FMR-1 gene) will transmit the premutation to their daughters, and subsequent grandchildren get the full mutation.
The presence of AGG interruptions within FMR1 CGG repeats contribute to the ….. The …. was larger for alleles lacking the AGG interruptions.
The presence of AGG interruptions within FMR1 CGG repeats contribute to the stability of the alleles. The magnitude of the repeat expansion was larger for alleles lacking the AGG interruptions.
The two main methods used to diagnose FXS
- Southern Blot analysis to measure the degree of methylation 2. PCR to discriminate small differences in the gray zone and premutation sizes
The presence of AGG interruptions within FMR1 CGG repeats contribute to the ….. The magnitude of the repeat was larger for …
The presence of AGG interruptions within FMR1 CGG repeats contribute to the stability of the alleles. The magnitude of the repeat expansion was larger for alleles lacking the AGG interruptions.
Cadherins - definition - types
- Calcium dependent glycoproteins that mediate adhesive interactions b/w cells of the same type (homotypic) or b/w cells of different types (heterotypic). - Types: N (neural), P (placental), and E (epithelial)
Adapter proteins are recruited to act as
Adapter proteins are recruited to act as linkers that either directly or indirectly connect cadherins to the cytoskeleton.
Two examples of adapter proteins
alpha and beta catenin
Cell-Adhesion Molecules (CAMs)
- cadherins - selectins - integrins - Immunoglobulin superfamily (Ig)
Selectins
- calcium dependent vascular adhesion molecules (glycoproteins) - produced by endothelial cells (epithelium lining blood vessels) - three members: E-selectin (endothelial-leukocyte adhesion molecule), P-selectin (recruitment of Platelets, and L-selectin (found on leukocytes)
Selectin - response to inflammation/foreign substance
- cytokines stimulate endothelial cells, which releases Selectins - E and P selectins interact with leukocytes to slow them down, and recruit them to site of infection
Overexpression of E-selectin and breast cancer:
Overexpression of E-selectin in the vascular endothelium is associated with more positive lymph node metastasis in breast cancer
Down regulation of E-Cadherin and cancer:
Down regulation of E-Cadherin decreases the strength of intercellular adhesion and enhances cellular motility - increase risk of cell metastasis in cancer.
Loss of E-cadherin and cancer:
In cancer, loss of E-cadherin leads to disintegration of the E-Cadherin - Catenin complex, resulting in the release of signal molecules for cell invasiveness
Integrins
- glycoproteins primarily acting as receptors for ECM components such as fibronectin, collagen, and laminin - also involved in inflammatory response by binding tightly to leukocytes - through InterCellular Adhesion Molecule, I (ICAM-1)
Leukocyte adhesion deficiency
- caused by a rare genetic defect in the synthesis of an integrin - persons with this disorder are susceptible to repeated bacterial infections and non-healing wounds
In normal tissue, laminin-332: But, in some tumors, laminin-332 …
In normal tissue, lamini-332 acts to attach cells to the basement membrane, and inhibit their movement. But, in some tumors, laminin-332 promotes cell migration.
Defective laminin are the basis for:
- a form of muscular dystrophy - junctional epidermolysis bullosa - lethal skin blistering disease - nephrotic syndrome - defects of the kidney filtration system
An agonist is a ligand that
activates signal transduction
An antagonist is a ligand that
prevents signal transduction
Hormone Response Element
in hormones, this is the DNA binding region (promoter region) to which the receptor-ligand complex binds to alter gene expression
Four major classes of cell surface receptors (intracellular signal transduction)
- ligand-gated ion channel receptors - enzyme-linked receptors - cytokine receptors - G-protein-coupled receptors
Intercellular signal transduction is
cell to cell communication
Intercellular signaling mechanisms:
autocrine, juxtacrine, paracrine, and endocrine signals
Cell surface receptors are binding sites for molecules that are:
- usually hydrophilic - too big to cross cell membrane
Ligand-gated ion channels
Ligand binds to receptor on cell surface → Activates receptor → Conformational change in receptor → channel opens → ions enter cell. Note: receptor and channel are same protein in this case
Enzyme-Linked Receptors
Ligand binds to receptor on cell surface → Conformational change in receptor → Activates the enzymatic portion of the receptor (on the cytosol side of membrane) → target response
Receptors Tyrosine Kinase (RTK)
An example of enzyme-linked receptors: Ligand binds to receptor on cell surface → Conformational change in receptor → Activates the enzymatic portion of the receptor (on the cytosol side of membrane) → Autophosphorylation (receptor activates its own tyrosine residues) → Phosphorylated tyrosine sites on receptor serves as a binding site for other signaling proteins → Signaling proteins are phosphorylated
Enzyme-Linked Receptor Serine-Threonine Kinases
Function in the same way as RTKs, but phosphorylates serine or threonine residues
Most Receptors Tyrosine Kinases (RTKs) with autophosphorylation typically influence cell … and …., and are often called ….
Most Receptors Tyrosine Kinases (RTK) with autophosphorylation typically influence cell proliferation and differentiation, and are often called growth factors.
Cytokine Receptors
Cytokine receptors are polymers Ligand binds to receptor → Receptors dimerize (come together) → Activation of a cytoplasmic tyrosine kinase → Tyrosine kinase phosphorylates tyrosine residues on the cytoplasmic tail of the receptor → Phosphorylated tyrosine residues can now bind to gene regulatory proteins → Gene regulatory proteins are phosphorylated → Phosphorylated gene regulatory proteins translocated to nucleus → Binds DNA and activates transcription
The JAK-STAT pathway is an example of a …. pathway. JAK is a cytoplasmic … STATs are … Dysregulation of this pathway is associated with various … like Crohn’s disease and asthma.
The JAK-STAT pathway is an example of a cytokine receptor pathway. JAK is a cytoplasmic tyrosine kinase. STATs are transcription factors. Dysregulation of this pathway is associated with various immune disorders like Crohn’s disease and asthma.
TGF-β and SMADs are examples of ligands that bind Receptor …. Kinases, and are central to … and … pathways. Mutations in these receptors results in progression of ….
TGF-β and SMADs are examples of ligands that bind Receptor Serine-Threonine Kinases, and are central to inflammation and fibrosis pathways. Mutations in these receptors results in progression of cancers.
G-proteins (guanine nucleotide-binding proteins) are … proteins. G-proteins bound to …. are ON, bound to … are OFF.
G-proteins (guanine nucleotide-binding proteins) are regulatory proteins. G-proteins bound to GTP (guanine triphosphate) are ON, bound to GDP (guanine diphosphate) are OFF.
G-Protein Coupled Receptors (GPCR):
- seven transmembrane domain receptors - superfamily of receptors that bind to a diverse group of ligands Ligand binds to receptor → Activates the receptor → Activated receptor binds to the α subunit of the G-protein complex → α subunit binds to GTP → α subunit dissociates from GPCR complex → α subunit binds to effector, activating it
Heterotrimeric G-protein complexes have 3 subunits:
- α subunit - β subunit - γ subunit
Effector
Small molecule that selectively binds to a protein and regulates its biological activity
Three classes of effectors:
- enzymes - accessory proteins (adaptor proteins) - second messengers
Enzyme effectors for G-protein signaling cascade
adelynate and guanylate cyclases
Second messengers are: Second messengers greatly:
Second messengers are intracellular signaling molecules that relay signals b/w the cell surface receptors (1st messengers) and target molecules in the cytosol or nucleus. Second messengers greatly amplify the strength of the signal transmission.
Three classes of second messengers
- cyclin nucleotides (cAMP and cGMP) - Inositol triphosphate (IP3) and Diagylglycerol (DAG) - Calcium ions
IP3 stimulates the release of … from the …, whereas DAG is a physiological activator of …
IP3 stimulates the release of calcium ions from the SER, whereas DAG is a physiological activator of protein kinase C (PKC).
cGMP (cyclic guanosine monophosphate) acts as a second messenger to activate
protein kinases
Termination of signal transduction
- reducing ligand availability 2. administration of an antagonist 3. Endocytosis of the agonist-receptor complex 4. Modifying receptor to inactivate it 5. Control of the 2nd messengers
Knudson’s 2-hit hypothesis
hypothesis that cancer is a result of accumulated mutations in DNA
The immune system, plays a critical role in …, …., and …. of cancer and pre-cancerous cells.
The immune system, plays a critical role in surveillance, prevention, and elimination of cancer and pre-cancerous cells.
Leukemias and Lymphomas are the most common cancers associated with the immunodeficiency. Why?
Blood cells have highest turnover rate, meaning more cell divisions. This increases the chance of replicating (and proliferating) mutated cells.
Damage to the Bone Marrow predisposes to leukemia. Why?
Damaged bone marrow means increased production of cells, increasing risk of proliferation of mutated cells.
Transcription activators are potent for genes that are very … Transcription activators can inappropriately activate … that can lead to …
Transcription activators are potent for genes that are very active, for example Immunoglogin genes. Transcription activators can inappropriately activate oncogenes that can lead to cancer.
An oncogene is one that has ….. Oncogenes control …. and …
An oncogene is one that has potential to cause cancer. Oncogenes control cell proliferation and apoptosis.
Chromosome instability, or “fragility” greatly increase … and … damage. With Damaged …, failure to … or to undergo …. allows persistence of mutations - possibly leading to ….
Chromosome instability, or “fragility” greatly increase chromosomal mutations and DNA damage. With Damaged DNA, failure to repair or to undergo apoptosis allows persistence of mutations - possibly leading to cancer.
The bcr gene is found on
chromosome 22
Translocation between chromosome 9 and chromosome 22 results in a gene that codes for the …, which is a …. that is constantly activated, resulting in …
Translocation between chromosome 9 and chromosome 22 results in a gene that codes for the bcr-abl fusion protein, which is a tyrosine kinase that is constantly activated, resulting in unregulated cell division.
Chronic Myelogenous Leukemia (CML) results from:
Chronic Myelogenous Leukemia (CML) results from the uninhibited activity of the bcr-abl protein.
Imatinib (Gleevec) is a drug used in the treatment of CML. It works by …
binding to the bcr-abl protein, and prevents phosphorylation, thereby inhibiting its tyrosine kinase activity.
Uninhibited activity of growth factors, through mechanisms such as: Loss of imprinting:…. or loss of heterozygosity:… can lead to …
Uninhibited activity of growth factors, through mechanisms such as: Loss of imprinting: activation of alleles is dysregulated or loss of heterozygosity: only one allele is expressed can lead to cancer.
How does embryology compare to cancer?
Embryology is regulated growth. Cancer is dysregulated growth… in a delicate balance.
Epidermal Growth Factors (EGFs)
Epidermal growth factors (EGFs) induce proliferation in epidermal cells. EGFs have high affinity binding to epidermal growth factor receptor (EGFR), encouraging cell division in EGF-receptive cells.
Mitogen
a chemical that triggers mitosis by activating signal transduction pathways in which mitogen-activated protein kinase (MAP kinase) is involved.
The ErbB family of receptors consists of:
- EGFR (aka HER1 or ErbB-1) - HER2 (aka ErbB-2) - HER3 (aka ErbB-3) - HER4 (aka ErbB-4)
HER2 gene is considered a proto-oncogene, meaning it …. HER2 is considered an oncogene when it leads to ….
HER2 gene is considered a proto-oncogene, meaning it regulates cell growth. HER2 is considered an oncogene when it leads to uncontrolled cell growth.
The HER2 gene is overexpressed in approximately …% of …
15% of breast cancers
HER2 has no ligand-binding activity, but activates by …, especially ….
HER2 has no ligand-binding activity, but activates by dimerizing with other HER molecules, especially HER3.
The HER2 gene is found on chromosome …
17
In HER2+ breast cancers, the HER2 gene is:
In HER2+ breast cancers, the HER2 gene is amplified, leading to protein overexpression. The resulting increase of receptors on the cell surface promotes receptor activation, excessive cellular division, and formation of tumors.
The Luminal A subtype for breast cancer tend to be
ER+ and/or PR+, HER2-, low Ki67
Ki67 is a
marker for cell proliferation
The Luminal B subtype for breast cancer tend to be
ER+ and/or PR+, HER2+, (or HER2- with high Ki67)
The Basal-like subtype for breast cancer tend to be
ER-, PR-, HER2-
The HER2 subtype for breast cancer tend to be
ER-, PR-, HER2+
Breast cancer luminal A subtype is the most … type with the … survival rate.
Breast cancer luminal A subtype is the most prevalent type with the best survival rate.
Breast cancer basal-like subtype has the …. survival rate.
worst
Prognostic markers in cancers are capable of providing information on … at the time of diagnosis. Such markers are usually indicators of .., … and …
Prognostic markers in cancers are capable of providing information on clinical outcome at the time of diagnosis. Such markers are usually indicators of growth, invasion, and metastatic potential.
Predictive markers in cancers are a measurement that predicts …
Predictive markers in cancers are a measurement that predicts response or lack of response to a specific treatment.
ER (estrogen receptor) positive breast cancers have a … than ER negative.
ER (estrogen receptor) positive breast cancers have a higher survival probability than ER negative.
BRCA 1 and BRCA 2 genes are …. genes, coding for proteins found in breasts that are involved in ….
BRCA 1 and BRCA 2 genes are tumor suppressor genes, coding for proteins found in breasts that are involved in repairing breaks in double-stranded DNA.
Mutations in BRCA 1 or 2 genes, leads to …, and this increases …
Mutations in BRCA 1 or 2 genes, leads to damaged DNA not being repaired, and this increases risk for breast cancer.
BRCA 1 or 2 mutations are inherited in
autosomal dominant manner
BRCA 1 or 2 mutations increase lifetime risk of cancers. For breast cancer, the risk is about …., ovarian …, and also increases risk of …. in males.
BRCA 1 or 2 mutations increase lifetime risk of cancers. For breast cancer, the risk is about 50-85%, ovarian 15-40%, and all increases risk of breast and prostate cancer in males.
In Oncotype DX assays, the Recurrence Score (RS) is based on several …, including …, …, and …
In Oncotype DX assays, the Recurrence Score (RS) is based on several expression patterns, including proliferation, estrogen, and HER2.
Tamoxifen, an inhibitor of estrogen receptors in breast tissue, is most … in patients with … tumors that are …
Tamoxifen, an inhibitor of estrogen receptors in breast tissue, is most beneficial in patients with low risk or intermediate risk tumors that are ER+/PR+
Chemotherapy is most beneficial in patients with … tumors.
Chemotherapy is most beneficial in patients with high risk tumors.
Adjuvant therapy refers to ….
Adjuvant therapy refers to additional treatment, usually given after surgery, and there’s a statistical risk of relapse due to occult metastasis.
Neoadjuvant therapy, in contrast to adjuvant therapy, is given … the main treatment. The most common reason for neoadjuvant therapy is to …. to facilitate more effective surgery.
Neoadjuvant therapy, in contrast to adjuvant therapy, is given before the main treatment. The most common reason for neoadjuvant therapy is to reduce the size of the tumor to facilitate more effective surgery.
When breast cancer cells spread, the cancer cells first spread to: Breast cancer often metastasize to which organs?
When breast cancer cells spread, the cancer cells are often found in lymph nodes near the breast. The most common places breast cancer can spread to are the bones, liver, and lungs.
Name the stages of breast cancer
- Stage 0: Ductal carcinoma in situ (DCIS): Abnormal cells are in the lining of a duct. - Stage I: early stage of invasive breast cancer. Cancer cells have not spread beyond the breast. - Stage II: The tumor is 2-5 cm and has spread to the lymph nodes under the arm. - Stage III: locally advanced cancer. The tumor has spread to underarm lymph nodes and to lymph nodes behind the breastbone. - Stage IV: distant metastatic cancer. The cancer has spread to other parts of the body, such as bone, liver or lungs.
Neoadjuvant therapy
Neoadjuvant therapy, in contrast to adjuvant therapy, is given before the main treatment. The most common reason for neoadjuvant therapy is to reduce the size of the tumor to facilitate more effective surgery.
When breast cancer cells spread locally, the cancer cells first spread to: Breast cancer often metastasize to which organs?
When breast cancer cells spread, the cancer cells are often found in lymph nodes near the breast. The most common places breast cancer can spread to are the bones, liver, and lungs.
When cancers metastasize, are the cells at new tumor site same or different from primary tumor?
When cancers metastasize, the new tumor has the same kind of abnormal cells. E.g. If breast cancer spreads to the bones, the cancer cells in the bones are still breast cancer cells and this is classified as metastatic breast cancer, NOT bone cancer.
Besides blocking signal transduction, Herceptin’s effectiveness is also due to …
Besides blocking signal transduction, Herceptin’s effectiveness is also due to it being an antibody and when bound to cells, it induces immune cells to kill those cells.
Selective Estrogen Receptor Modulators (SERMs) work by:
Selective Estrogen R eceptor Modulators (SERMs) work by binding to the estrogen receptors and inhibiting estradiol’s stimulation of transcription. This reduces cellular proliferation and enhances apoptosis of cancerous cells.
For breast cancer treatment, why are aromatase inhibitors used in post-menopausal women as opposed to Tamoxifen? Why not premenopausal women?
Post-menopausal women no longer synthesize estrogen in ovaries; estrogen is produced in peripheral tissues. Aromatase inhibitors inhibit estrogen at the site of cancer (adipose tissue of breasts). If used in premenopausal women, the decrease in local estrogen would activate the hypothalamus, and the ovaries would increase estrogen production.
Which test (analysis) is used to identify overexpression of HER2 proteins?
Immunohistochemistry (IHC): amount of HER2 protein present determined by a lab test and assigned a score from 0 (negative) to 3+ (highly positive).
Taxol is a chemotherapeutic drug that:
Taxol is a chemotherapeutic drug, that is a antimicrotubule agent, and works by inhibiting microtubule formation within the cell, therefore inhibiting cell replication and division.
What is Trastuzumab emtansine (T-DM1)?
Trastuzumab emtansine (T-DM1) is an antibody-drug conjugate consisting of the monoclonal antibody trastuzumab linked to the cytotoxic agent DM1 used in the treatment of HER2+ breast cancers.
What is Xeroderma pigmentosum (XP)?
- XP is a rare, autosomal recessive disorder - Mechanisms to repair DNA damage caused by ultraviolet (UV) light is deficient - characterized by sun sensitivity and UV radiation–induced skin and mucous membrane cancers.
Anthracycline is a chemotherapeutic drug that works by:
- Inhibiting DNA and RNA synthesis - Creating iron-mediated free oxygen radicals that damage the DNA and cell membranes
XP results from mutations in the … pathway genes (XP-A to XP-G complement groups), which are required for repair of ….
XP results from mutations in the seven Nucleotide Excision Repair (NER) pathway genes (XP-A to XP-G complement groups), which are required for repair of UV-damaged DNA.
XP-Variant has normal …, and is caused by deficiency in DNA …, which normally …
XP-Variant has normal NER, and is caused by deficiency in DNA polymerase η (eta) encoded by POHL gene. DNA pol η normally replicates over damaged DNA
UV light can produce dimerization of two adjacent …. that prevents … from replicating the DNA beyond the site of dimer formation.
UV light can produce dimerization of two adjacent pyrimidines (usually thymines) that prevents DNA polymerase from replicating the DNA beyond the site of dimer formation.
The Nucleotide Excision Repair (NER) pathway uses ….
The Nucleotide Excision Repair (NER) pathway uses UV specific endonucleases to recognize and excise dimers caused by UV light.
XP-Variant has normal …, and is caused by deficiency in DNA ….
XP-Variant has normal NER, and is caused by deficiency in DNA polymerase η (eta), which normally replicates over damaged DNA.
UV light can produce dimerization of two adjacent …. that prevents DNA polymerase from …
UV light can produce dimerization of two adjacent pyrimidines (usually thymines) that prevents DNA polymerase from replicating the DNA beyond the site of dimer formation.
More than half of the XP cases in the US result from mutations in which three genes?
XPC, XPD, and POLH
XP can be diagnosed on the basis these clinical findings:
Clinical findings: skin sensitivity to sun, neurological impairments, vision problems (photophobia)
Treatment of XP includes:
- avoidance of UV - topical application of 5-fluorouracil to treat actinic keratoses (rough, scaly skin) - regular evaluation by an ophthalmologist, dermatologist, and neurologist
Approximately what percentage of XP patients have progressive neurological degeneration? Usually these patients have defects in which 4 genes?
Approximately 25% of XP patients have progressive neurological degeneration, usually these patients have defects in the XPA, XPB, XPD, or XPG genes.
What is the primary cause of death in XP patients?
cancer
Three related disorders of defective DNA repair:
- XP - Trichothiodystrophy (TTD) - Cockayne syndrome (CS)
Herceptin (trastuzumab), is a
monoclonal antibody used in the treatment of HER2+ breast cancers.
Laboratory tests/studies for XP diagnosis:
Molecular testing/DNA functional array analysis: • Cellular hypersensitivity to UV radiation and chromosomal breakage studies • Unscheduled DNA synthesis: measures cells’ ability to perform excision repair • Complementation tests • Gene sequencing
Some of the neurological impairments associated with XP are:
- Sensorineural hearing loss - Absent deep tendon reflexes - Progressive intellectual impairment - Slurred speech - Loss of ability to walk - Difficulty in swallowing and requirement for the use of a feeding gastrostomy
Possible Etiology behind neurological impairments found in XP
Neurodegeneration probably results from accumulation of mutations from cells inability to repair DNA damage, not just UV damage but also damage from other mutagens such as free radicals, species from oxidative metabolism.
Pertuzumab is similar to Traztuzumab, inhibiting HER2 activity, but binds to a …. than Traztuzumab. Pertuzumab can be used in combination with Traztuzumab to ….
Pertuzumab is similar to Traztuzumab, inhibiting HER2 activity, but binds to a different extracellular domain of HER2 than Traztuzumab. Pertuzumab can be used in combination with Traztuzumab to enhance effects.
Ductal carcinoma involved two sequential processes:
- uncontrolled cell proliferation 2. invasion/infiltration of stroma
factors controlling normal epithelial cell proliferation:
- continuous cell turnover: rate of proliferation = rate of cell death 2. presence of committed amplifying daughter cells 3. regulation of signaling pathways 4. regulation of integrin signaling (b/w cell and its environment)
With the loss of E-cadherin, N-cadherin is…
up-regulated in breast cancer. N-cadherin is not usually expressed in normal mammary epithelium.
Integrins and cancer:
- integrin activation down-regulated E-cadherin, decreasing the strength of intercellular adhesion and allowing cellular motility - Integrin signaling modulate expression of MMPs, which break down various components of the matrix, thus allowing passage of cells
In cancer, Vascular Endothelial Growth Factor (VEGF) is
upregulated, stimulating the formation of vasculature for metastasized tumor
Laminin
- major protein of cell-associated matrices and basement membrane - consists of functional domains that binds to cells, as well as collagen and other matrix molecules - binds cells to basement membrane
Most cancer drugs target cells at what stage (s) of the cell cycle?
In the DNA synthesis or mitosis (cell division) stages
Chemotherapy
- chemical agents that are used in the treatment of cancer - traditionally, most chemotherapy drugs were cytotoxic, aimed at killing cells that divide rapidly
Topoisomerase inhibitors are used in cancer treatment. They work by…
inhibiting DNA supercoiling and therefore inhibiting synthesis of DNA, resulting in cell death
Alkylating agents in cancer treatment
- alkylating agents are used in the treatment of cancer to kill cells by damaging DNA - cancer cells proliferate faster and with less error-correcting than healthy cells, cancer cells are more sensitive to DNA damage — such as being alkylated
Two examples of alkylating agents used in cancer treatment
- nitrogen mustards - platinum
Antimetabolites in cancer treatment
masquerades as purines or pyrimidines, blocking DNA synthesis
Vinca Alkaloids
- anti-microtubular drugs that inhibit the assembly of tubular into microtubules - leading to prolonged mitotic delay and results in cell death
Taxanes
- class of anti-microtuble agents used in cancer treatment - enhances the stability of microtubules, inhibiting cell division
Epothilones
- class of anti-microtuble agents used in cancer treatment - enhances the stability of microtubules, inhibiting cell division
What are the hallmarks of cancer?
- sustaining proliferation - evading growth suppressors - activating invasion and metastasis - replicative immortality (increased telomerase activity) - inducing angiogenesis - resisting cell death
Driver mutations
Mutations that promote growth and progression of cancer as opposed to those that don’t (passenger mutations)
Transcription-coupled repair:
removes damage from actively transcribed genes
Global genome repair
removes damage from genes (actively transcribed and non transcribed)
In Transcription-coupled repair, CSA and CSB genes …
recognizes damaged DNA
In Global genome repair, XPE and XPC genes…
recognizes damaged DNA
NER pathway, after damage recognition, DNA unwinding is done by which genes?
- XPB and XPD (helicases) - XPA and replication protein A (RPA)
NER pathway, XPF and XPG are
endonucleases that make incisions to remove lesions
DNA polymerase η (eta) is encoded by what gene?
POLH
At which steps are NADH molecules produced in the TCA cycle?
- Isocitrate and NAD+ w/ isocitrate dehydrogenase → oxalosuccinate and NADH - α-Ketoglutarate and NAD+ and CoA w/ α-Ketoglutarate dehydrogenase → Succinyl CoA and NADH and CO2 - Malate and NAD+ w/ malate dehydrogenase → oxaloacetate and NADH
At which step is FADH2 produced in the TCA cycle?
Succinate w/ succinate dehydrogenase → fumarate and FADH2
At which step is GTP produced in the TCA cycle?
Succinyl CoA and GDP and Phosphorous w/ Succinyl CoA synthase → Succinate and GTP
Mortality rate in XP patients with neurological degeneration compared to those without neurological degeneration:
XP patients with neurological degeneration, median age of death 29 years old, have a higher mortality rate then XP patients without neurological degeneration, median age of death 37 years old.
