Unit III Flashcards
Anchorage Independence
The ability to grow without attachment to solid substrate.
A property of cancer cells.
Five different properties of malignant cancer cells
- Anchorage Independence
- Immortalization - can proliferate indefinitely
- Loss of contact inhibition - ability to grow over one another
- Insensitivity to anti-growth signals
- Tissue invasion and metastasis
Multi-step process for cancer
- Noraml cell
- Inreased proliferation
- Early/ progressive neoplasia
- Carcinoma - tumor developed
- Metastatsis - spreading through the circulatory system
- Turn on oncogene
- Turn off tumor suppressor (both cell cycle regulatory and DNA repair genes).
- Turn off apoptotic genes
What types of genes are usually mutated in tumor initiation?
Oncogenes and Tumor Suppressors
Familial Rb is more prone to what type of tumor?
Bilateral
Sporadic Rb is prone to what type of tumor?
Unilateral.
It’s much more unlikely to have the same two sporadic muations in both eyes.
Rb within the cell cycle
is an inhibitor of cells moving from the G1 to S phase
Inhibitor of Rb?
Cyclin D and E which phosphorylate Rb
How does loss of heterozygosity occur?
- Mutation
- Mitotic recombination
- Chromosome loss
- and/or environmental factors
Explain the Knudson Theory
If you’re heterozygous, you have one strike against you through your genes ( one copy of suppressor gene knocked out in your parents’ passed on DNA). If you have another “strike” (such as UV exposure causing an unrepaired mutation in the other copy), you’re unable to produce that tumor suppressor gene at all - leads to cancer.
Ways to inactivate tumor suppressor
Translocations
Loss of heterozygosity - RB
Examples of dominant inherited cancer
Familial Retinoblastoma (RB) Adenomatous Polyposis (FAP-APC gene) Familial Breat and Ovarian Cancer (BRCA1 and BRCA2 genes) Wilms tumor
Examples of Recessive inherited cancer
Xeroderma Pigmentosa (XP genes)
Aataxia-Telangiectasia (AT gene)
Bloom’s syndrome
Fanconi’s Congenital aplastic anemia (FA genes)
Describe the inheritance pattern of Rb
It is an autosomal dominant disorder (consistent when drawing a family pedigree) however, it is a RECESSIVE disorder in which loss of heterozygosity and removal of both Rb genes in a cell leads to uncheck proliferation of cells
Is Rb an oncogene or tumor suppressor?
tumor suppressor (anti-oncogene)
Function APC gene
encodes a cytoplasmic protein that keeps beta-catenin outside the nucleus; without APC, beta-catenin goes into the nucleus and beings uncontrolled transcription of oncogenes like c-myc.
Function of the BRCA 1 gene
Breast Cancer Gene 1: encodes scaffold protein that checks the cell cycel to make sure that DNA has replicated correctly. When this gene is mutated, this surveillance on the cell cycle is removed.
What type of gene is BRCA1 and 2?
tumor suppressor
What type of gene is p53
Originally thought to be an oncogene because a p53 mutation was dominant to the wild type gene in producing cellular transformation. Now we know that the p53 mutation produces a mutant PROTEIN that binds to the wild type p53 to inactivate it - CLASSIC TUMOR SUPPRESSOR.
What gene is referred to as “spoiler” or “monkey wrench”?
p53
Why is p53 considered the “guardian of the genome”?
- Acts as a transcription factor which prevents cells from replicating damaged or foreign DNA
- It is required for cell apoptosis, cells with damaged DNA commit suicide
- Interferes with the life cycle of human viruses including Adenovirus and HPV
What genes does HPV try to inactivate?
Rb and p53
What are the three genes found in a viral RNA?
- gag gene
- env gene
- poly gene
Function the gag gene?
Found in viral RNA
codes for internal virion protein
Function of the env gene?
Found in viral RNA
codes for viral membrane glycoproteins
Function of the pol gene?
Found in viral RNA
codes for a virus polymerase
What gene is needed to produce sarcoma?
v-onc gene segment
HPV E6
protein that inhibits p53
HPV E7
protein that binds to and inhibits Rb
function of pp60v-src
A protein coded by the v-src oncogene and is a membrane-bound protein kinase that phosphorylates tyrosine residues. Changes the properties of cells by affecting gene expression
function of the v-erb-B
Oncogene that codes for a protein that is similar in structure to the cell surface receptor for epidermal growth factor (EGFR).
v-abl
oncogene that codes for a protein kinase that phosphorylates tyrosine residues on other proteins.
v-src
oncogene of Rous Sarcoma Virus causing fibrosarcomas in birds
v-myc
oncogene usually fused with portion of the gag gene. Capable of eliciting neoplastic transformation of cells
How are oncogenes used as molecular markers in prognosis?
The level of expression of oncogenes tends to correlate with the rapidity of the progress of the cancer
Example of oncogenes used for prognosis?
- The level of expression of the N-myc gene used in prognosis analysis for neuroblastoma
If you have greater than 10 copies of n-myc death is accelerated
- HER/neu oncogene encodes integral membrane protein kinase and is amplified in 20% of breast cancers
Targeting oncogenes
Herceptin - drug antibody therapy agains the HER2/erb2 oncogene product
Gleevec - inhibits ABL tyrosine kinase specific to the ATP binding site
Targeting tumor repressors
Inject RB directly into Rb-negative tumors
Use drug that only kills cells with p53 deficiencies
Use a drug that corrects the mutant conformation of the dominant-negative p53 proteins
Diagnostic Criteria for LFS
I. Proband with sarcoma diagnosed before 45 years of age AND
II. A first-degree relative with any cancer under 45 years of age AND
III. A first or second-degree relative with any cancer under 45 years of age or a sarcoma at any age
Diagnostic Criteria for Li Fraumeni Like Syndrome
I. Proband with any childhood cancer or sarcoma, brain tumor, or adrenal cortical tumor diagnosed before 45 years of age AND
II. A first- or second-degree relative wit ha typical LFS cancer (sarcoma, breast cancer, brain tumor, adrenal cortical tumor, or leukemia) at any age AND
III. A first- or second-degree relative with any cancer under the age of 60 years
What is Von Hippel-Lindau syndrome?
Formation of cystic and vascularized tumors in many organs
What is the pattern of inheritance for Von-Hippel Lindau syndrome?
Autosomal dominant
What are the major causes of death in patients with Von Hippel-Lindau?
Metastatic Renal Cell Carcinoma
CNS hemangioblastomas
Percent of VHL cases caused by sporadic mutations?
20%
What type of gene is the VHL gene?
tumor suppressor gene
clinical manifestations of Von Hippel-Lindau (VHL) disease.
Cerebellar and spinal cord hemangioblastomas
Retinal hemangioblastomas
Bilateral kidney cysts and clear cell renal cell carcinomas (RCC)
Pheochromocytomas
Pancreatic cysts and pancreatic neuroendocrine tumors
Endolymphatic sac (inner ear) tumors (ELST)
Cystadenomas of the genitourinary tract (epididymal, broad ligament)
Type 1 VHL
Type 1: Hemangioblastoma + clear cell renal cell carcinoma
low risk of pheochromocytomas
due to total loss or partial loss of VHL
Type 2a VHL
Hemangioblastoma and pheochromocytoma
low risk of renal cell carcinoma
high risk for pheochromocytoma
due to VHL missense
Type 2b VHL
hemangioblastoma, clear cell renal cell carninoma, pheochromocytoma (high risk)
due to VHL missense
Type 2c VHL
pheochromocytoma only
due to VHL missense
Where is the VHL gene located?
chromosome 3 (3p25-26)
Actions of the VHL protein?
Regulation of hypoxia inducible transcription factor (HIF)
suppression of aneuploidy
maintenance of primary cilia and stabilization of microtubules
HIF under normoxic conditions?
HIF is hydroxylated and is then ubiquitinated by VHL wild type and undergoes proteosomal degradation
HIF under hypoxic condition?
HIF does not get hydroxylated and goes straight to nucleus and activate transcription of genes that are involved in angiogenesis (development of new blood vessels), metabolism, apoptosis, and other processes that promote cancer growth and survival under low O2.
factors that affect surrounding vasculature
Main mechanism for clear cell renal cell carcinoma?
sporadic mutations
VHL loss or mutation is responsible for about 2/3rd of these sporadic cases
Only 4% of these cases are inherited.
Therapies used to treat clear cell renal cell carcinoma?
block thevascular endothelial growth factor (VEGF), m-TOR, HIF-2a inhibitors.
Immunotherapies used to stop the down-regulation of immune system typically seen in cancers.
Define ionotropic receptors
Neurotransmitter receptors directly coupled to ion channels (ex: the receptor and channel are part of the same protein).
Selectivity of pentameric ligand-gated channels
selective for the permeation of chloride, or allow permeation of both sodium and potassium (with slight preference for sodium)
Describe the structure of pentameric ligand-gated channels
Heteropentamers
5 subunits
each subunit has 4 transmembrane alpha helices
M2 alpha helices assembles around the ion-conducting pathway
Structure of ionotropic glutamate receptor
tetrameric ligand-gated channels
Selectivity of of ionotropic glutamate receptor
two of the four subunits bind glutamate
other two bind glycine
Apical Surface
Faces the mucosal lining or lumenal lining. usually contains special transporters
Basolateral Surface
Exposed to interstitial fluid and usually has generic transport properties like plasm membranes of non epithelial cells
Where is the Na/K pump located?
Basolateral membrane
Describe the permeability of Na and K in the basolateral membrane.
low sodium permeability
high potassium permeability
Describe the permeability of Na and K in the apical membrane.
highly permeable to sodium
low potassium permeability
What is the maximum diameter for transported particles through the nuclear pore complex?
39 nm
What is the role of Karyopherins?
They directly interact with the phenylalanine (F) and glycine (G) Nups or with the cargo itself.
Interacts with the nuclear pore complex
What source of energy is used to transport mRNA outside of the nucleus?
ATP
Smooth ER is important for..?
Making lipids
What is the Signal Recognition Particle (SRP)?
It recognizes the signal sequence on a protein and binds to it.
Stops translation until bound by SRP receptor on ER.
What is the translocon?
A group of proteins that is a channel that forms a pore from one side of membrane to the other.
Type I transmembrane protein
Has COO- group in the cytoplasm and NH3+ group inside the ER
What causes Limb Girdle disease and Rippling Muscle disease
A mutation in the caveolin-3 gene which is expressed in skeletal and cardiac muscles
What are the two mechanisms that vesicles are formed?
- clathrin coat proteins
2. caveola
When do cells use ubiquitin-proteasome system (UPS)?
rapid degradation of proteins when fast adaptation is needed
Makes up about 1% of protein in cells
When do cells use Autophagy?
degradation of long-lived proteins and entire organelles
required for the adaptation to environmental stresses such as starvation
What is the function of Heat shock protein 70 (Hsp70)
helps fold a protein by binding to exposed hydrophobic patches in incompletely folded proteins and prevents aggregation
What is the function of Heat shock protein 60 (Hsp60)
forms an elaborate, large, barrel-shaped structure that acts
as an isolation chamber. Misfolded proteins are fed into the chamber to prevent aggregation and to help it to
refold.
What is the role of Bip?
chaperone protein that functions much like Hsp70 but uses ATP to help proteins fold
What is the role of ERp57?
located within the ER and is a a thiol oxidoreductase that allows formation of disulfide bonds
What are lectins?
Bind Sugars
Example lectins?
Calnexin and calreticulin
How many ubiquitins for proteosome to recognize?
4 ubiquitins in a ROW
What is the role of E3?
enzyme that transfers ubiquitin from E2 to a lysine in the protein and adds more ubiquitin
Order these in terms of the number of genes for these enzymes: E1, E2, E3 (smallest to largest)
E1
What is the importance of Nieman Pick disease?
They are resistant to Ebola because they have mutation in cholesterol transfer
Significance of proteasomes?
Peptides from these immunoproteasomes are
transported into the ER and bind to MHC class I luminal domains. The MHC class I molecule is a complex with
a transmembrane domain; this complex plus peptide progresses through the secretory pathway until the peptide
is on the extracellular surface of the cell. Immune cells recognize these peptides as self or foreign and
“immunology happens”.
Describe the process of Chaperone mediated autophagy.
5 AA motif KFERQ is recognized by Heat Shock Protein 70 (HSP70) which is recognized by a complex of proteins and directly delivered by a lysosomal receptor protein (LAMP-2A) directly into the lysosome, where the proteins are degraded
What is an amphisome?
An endosome fused with an autophagosome
What gene regulates autophagy?
ATG
What effect does rapamycin have on autophagy?
increases autophagy
What is the relationship between autophagy and apoptosis?
inversely related
Caspases cleave Beclin 1, switches off autophagy, letting apoptosis work more effectively
What is the role of Bcl-2 and Bcl-xL?
Bcl-2 and Bcl-xL bind to BH3 domains on Beclin 1 to inhibit autophagy
What is the role of Beclin 1 by itself?
Upregulates autophagy
What is the significance of BH3 mimetic ABT 737?
It disrupts the Beclin-1-Bcl-xl interaction and causes apoptosis to occur.
Recent findings are showing autophagy is also occuring so we need to tease this out for future research.
What is the significance of phospholipid phosphatidylserine (PS)?
When it is exposed to the outer leaflet macrophages have receptors for PS, and recognize, bind to, and ingest cells that have committed to the apoptotic pathway. Gives the cell no chance to lyse and release inflammation-causing molecules to the extracellular space.
What is the role of Bcl-2 and Bcl-XL?
anti-apoptosis
What is the role of Bim and PUMA?
pro-apotopic members that move to the mitochondrion and replace Bcl-2 and Bcl-XL. This allows other members of the same family, Bax and Bax, to act on the membrane, making it permeable so it releases cytochrome C into the cytoplasm
Caspase-9
signal caspase that activates caspase-3
Caspase-3
executioner caspase that cleaves many substrates, eventually resulting in the classic appearance of apoptosis
What molecule activates caspase-9?
activated Apaf-1
What activates Apaf-1?
cytochrome c in the cytoplasm
What is the significance of FAS Ligand?
the CTL upregulates expression of a surface molecule called Fas (or CD95) ligand (FasL, CD95L), which
then engages and cross-links a corresponding molecule on the abnormal cell’s surface, Fas or CD95
What is the role of activated Fas or CD95?
CD95 transduces a signal into the cell’s interior, which recruits to CD95 an adaptor molecule called FADD, which activates caspase-8. Caspase-8 then activates caspase-3 for apoptosis to occur?
What is the significance of FLIP?
It competes with caspase-8 for binding to FADD, and thus inhibits apoptosis signaling (
Define Statins
drugs used to lower cholesterol
What is the rate limiting step for the synthesis of cholesterol?
HMGCoA reductase (3-hydroxy-3-methylglutaryl coenzyme A reductase)
What is the significance of sterol regulatory
element binding protein (SREBP)?
Both uptake and synthesis are regulated by the sterol regulatory element binding protein (SREBP), a protein containing a transcription factor that regulates both
LDLR and all 30 of the synthesis proteins.
What is the transcription factor used to upregulate cholesterol synthesis?
basic helix loop helix (bHLH) DNA- binding protein that is held inactive because it is part of a larger transmembrane protein (SREBP). Only activated once it is cleaved off in the Golgi
role of Insig and SCAP?
when cholesterol is low, SREBP needs to move to the Golgi, where it is cleaved to release the transcription factor. Insig blocks the SCAP signal to recruit COPII. Therfore, Insig binds to SCAP when cholesterol levels are HIGH.
How is BHLH cleaved from SREBP?
via RIP, regulated intramembrane proteolysis within the Golgi
What are the three classes of lipids in a membrane?
phospholipids, sphingolipids, and cholesterol
What are the most common phospholipids in the membrane?
phosphatidylethanolamine (PE), phosphatidylcholine
(PC), phosphatidylserine (PS), and
phosphatidylinositol (PI).
What phospholipids are more prevalent within the inner leaflet of membrane?
Negatively charged phosphatidylserine (PS), phosphatidylethanolamine (PE), and phosphatidylinositol (PI)
What phospholipids are more prevalent in the outer leaflet?
Phosphatidylcholine PC, sphingomyelin, and glycolipids are
Where are most lipids made?
In the endoplasmic reticulum
Order these membranes from thin to thickest: ER, Golgi, and Plasma membrane
ER
What molecule does your body use to synthesize cholesterol?
acetate
What molecule do you need to break up the SNARE complex for recycling?
N-ethylmaleimide Sensitive Factor (NSF)
How many ATPs do you need to separate the SNARE complex?
6 ATPs; one for each subunit.
What is the role of alpha snap?
It binds to the SNARE complex and recruits NSF
What is the role of n-sec1?
binds to syntaxin to refold it and stays bound to prevent VAMP from binding. n-sec1 must be released before another SNARE complex can form.
What causes n-sec1 to release itself from syntaxin?
The release of calcium
Four major classes of molecules found in ECM
- glycosaminoglycans –> proteoglycans
- fibrous proteins such as collagen and elastin
- fibronectin and laminin
- Water and many solutes
