Intro, Cell Response, Toxins Flashcards
Block 1
What is the function of miRNAs?
Never translated, regulate gene expression via post-transcriptional silencing
What is heterochromatin? Euchromatin?
Heterochromatin- dense, inactive
Euchromatin- disperse, active
What does histone methylation do? Where does it occur?
At lysines and arginines; activation or repression
What does histone acetylation do? Where does it occur?
At lysines; activate
What does histone phosphorylation do? Where does it occur?
At serines; activation or repression
What does DNA methylation do?
Transcriptional silencing
Order of products in post transcriptional silencing
DNA, primary miRNA processed into pre-miRNA, exits nucleus, DICER trims pre-miRNA to DS miRNA, forms RISC
What does long noncoding RNA do (3)?
Modulate gene expression by facilitating TF binding (gene activation), binding TFs to prevent binding (gene suppression), binding DNA to promote modification
What is XIST an example of?
Long noncoding RNA gene suppression- in females, cloaks the X chromosome to silence
What do peroxisomes contain? What do they generate through breakdown of fatty acids?
Catalase, peroxidase; ROS (hydrogen peroxide)
Where is cholesterol in the cell membrane?
Inner and outer faces
Where is phosphatidylinositol in the cell membrane? Phosphatidylserine?
Inner and outer; inner mostly
Role of phosphatidylserine (3)
Confers negative charge to inner membrane
Eat me signal during apoptosis
In platelets, cofactor in blood clotting
Where are glycolipids and sphingomyelin in the cell membrane; purpose?
Extracellular face; cell-cell interactions
Phosphatidylinositol is hydrolyzed by phospholipase C to form what? What receptor stimulates this?
Generates 2nd signals like DAG and IP3; G-protein coupled
What is potocytosis?
Caveolae mediated, non-coated
What is pinocytosis?
Receptor mediated, clathrin coated
Three types of filaments, examples, and their purpose
Microfilaments- actin, structure and movement
Intermediate filaments- keratin, desmin, IHCs, cytokeratins, tensile strength and shape
Microtubules- cilia, flagella, move things around cell
What are occluding/tight junctions attached to? Adherens junctions?
Actin; Actin
What are desmosome and hemidesmosome junctions attached to?
Desmosomes- Intermediate filaments to transmembrane desmoglein
Hemidesmosomes- intermediate filaments to ECM (transmembrane integrins)
What proteins form tight/occluding junctions?
Claudin, TAMP- transmembrane
Zonula occludens, cingulin- intracellular
What three categories make up anchoring junctions? What type of proteins form anchoring junctions?
Adherens, Desmosomes, hemidesmosomes
Cadherins (cell adhesion)
Where is the adherens junction in the cell? Classic cadherin
Next to tight junction; e-cadherin
What does the desmosome do? Cadherins?
Links cells through intermediate filaments; desmoglein and desmocollin
What does the hemidesmosome do? Cadherin?
Links cells to ECM through intermediate filaments; integrins
What are gap junctions? Example?
Allow communication between cells; connexons
What cells have a lot of SER?
Steroid producing cells- gonads, adrenals
Hepatocytes (CYP450)
What is the unfolded protein response?
If excess abnormally folded proteins, cell reduces protein synthesis and increases chaperone proteins, then autophagy
What is the double membrane vacuole of autophagy derived from? what is it tagged with?
ER; LC3
What attaches ubiquitin to misfolded proteins?
E1, E2, E3 ubiquitin ligases
What are the membrane permeability transition pores?
Toxic or ischemic injury induces them, dissipates proton gradient (H+ leaves mitochondria), so ATP generation declines, Na/K pumps stop working, intracellular Na increases, cell swelling, necrosis
G protein coupled receptor pathway
receptor associates with GTP binding protein , exchanges GDP for GTP, activates phospholipase C, which generates 2nd messengers cAMP, IP3, DAG, IP3 triggers release of calcium from ER
Wnt ligands bind to __________, then….
Frizzled receptors (GPCR). recruits Dishevelled proteinthat disrupts beta catenin degradation complex, allowing it to go to nucleus and transcribe
Tyrosine kinase receptor (GF receptor) pathway)
Receptor dimerizes, autophosphorylates tyrosine residues, bridging proteins attach receptor to GDP bound (inactive) RAS, GDP replaced by GTP to activate RAS, which then activates RAF–>MAPK, or PI3K–>Akt–>mTOR
Pro-apoptotic proteins
BAX, BAK, BOK
Calcium storage in decreasing order
Mitochondria>ER>Cytosol
Examples of antioxidants
Vitamins A, C, E, and glutathione
Location and function of catalase
Peroxisomes, breaks down peroxide (H2O2)
Location and function of Superoxide Dismutase (SOD)
Cytosol and mitochondria; converts superoxide to H2O2
Location and function of glutathione peroxidase
Cytosol and mitochondria; converts H2O2 to H2O
Three ROS effects
Lipid peroxidation in membranes, forming peroxides
Oxidative modification of proteins
DNA lesions
What enzymes are activated by increased cytosolic Ca?
Phospholipases (membrane damage)
Proteases
Endonucleases
ATPases
Other antioxidants in the cytosol?
Vitamin C, ferritin, cerruloplasmin
Antioxidants in membranes
Vitamin E, A, and beta-carotene
Features of reversible cell injury
Swelling, loss of microvilli, membrane blebs, clumped chromatin, lipid, myelin figures
Features of irreversible cell injury
Pyknosis, karyorrhexis, karyolysis, absence of nuclei, cytoplasmic eosinophilia
Ultrastructural features of necrosis; what changes are reversible? Irreversible?
Swollen, rounded, detached
Swollen mitochondria with electron dense deposits
Swollen ER
Myelin figures (ceroid)
Reversible: small mitochondrial densities, detachment of ribosomes, clumping of chromatin
Only in irreversible cell injury: Large mitochondrial densities, loss of ribosomes, profound nuclear changes
AL amyloidosis is? Example? Made of
Primary; immune dyscrasias; lambda light chain of immunoglobulin
AA amyloidosis is? Example? Made of
Secondary; reactive or familial; serum amyloid A (IL1 and IL6 stimulate production)
Who gets AA amyloid in their glomeruli? Liver? medullary interstitium?
Abyssinians; siamese; shar-peis
What amyloidosis causes neurodegeneration? Made of
Abeta; amyloid precursor protein (APP)
What amyloidosis causes localized endocrine amyloid?
IAPP
Best stain for amyloid in cats
Thioflavin T
Which amyloid type retains congophilia after potassium permanganate? Which one loses congophilia?
AL; AA
What is the most common amyloidosis in animals?
AA
What causes lipofuscin? What does it stain with?
Lipid peroxidation of cell membranes; ORO, Sudan black, PAS+
What does melanin production require?
Tyrosine, tyrosinase (contains copper)
How does cyanide cause toxicity? How does this change the color of blood?
Binds and inhibits cytochrome C oxidase, so no oxidative phosphorylation; Oxygen remains on hemoglobin, so venous blood bright red
How does carbon monoxide cause toxicity? How does this change the color of blood?
Binds hemoglobin, replacing oxygen, forming carboxyhemoglobin, so blood cherry red
What is methemoglobin?
When ferrous iron is converted to ferric iron, does not bind oxygen as well
What is hemosiderin
Free iron bound by ferritin is converted to hemosiderin after accumulating in macrophages
How is hematoidin different?
Bright yellow, polarizes light, derived from hemosiderin, contains no iron, closely related to bilirubin
Where does bilirubin come from?
heme from hemoglobin, no iron, first converted to biliverdin, then to bilirubin
Which CDK inhibitors contribute to cellular senescence?
CDKN2A- p16 aka INK4a
Ultrastructural changes with apoptosis
Chromatin condensation into caps/crescents
Cell surface blebbing (apoptotic bodies)
Initiator caspases
2, 8, 9, 10
Executioner caspases
3, 6, 7
What caspase causes pyroptosis? via what?
Caspase 1; inflammasome
Also 4 and 5 (all inflammatory caspases)
What caspase is activated by p53 after DNA damage?
Caspase 2
What else stimulates caspase 3, 6, and 7?
Granzyme B from WBCs
What does caspase 8 do?
In extrinsic necrosis, forms death induced signal complex
What redirects cell to necroptosis? Outcome?
Inhibition of caspase 8; Necrosome forms from RIPK1, RIPK3, and FADD, which then phosphorylates MLKL
What does caspase 9 do?
In intrinsic necrosis, forms apoptosome in response to MOMP releasing cytochrome C
What does caspase 11 do?
Triggered by LPS and sepsis
How does apoptosis lead to phagocytosis? Name of process?
Phosphatidylserine flipped out, may become coated with antibodies and C1q; Efferocytosis
Triggers of necroptosis
TNF, FasL, DNA damage, LPS, interferon gamma via death receptors or TLR 3 and 4
Three possible responses to TNF binding TNFR1; what decides which fate?
- Survival through NFkappB signaling
- Extrinsic apoptosis through DISC formation
- Necroptosis
Ubiquitination of RIPK1
What is necroptosis?
Resembles necrosis morphologically, but occurs similarly to extrinsic apoptosis
Pro-inflammatory
Caspase-independent
What does MLKL do?
Polymerizes to form amyloid-like structure that disrupts cell membrane
What can inhibit necroptosis?
Caspase 8 cleavage of RIPK
Necrostatin
What triggers ferroptosis? What inhibits it? Why does it happen?
Excessive intracellular iron or ROS; Glutathione peroxidase 4; fenton reaction overwhelms glutathione, leading to ROS and lipid peroxidation
Ferroptosis morphologically resembles ___________.
Necrosis
Cause and result of pyroptosis; Initiated by ____________
Intracellular pathogens, pyrexia; caspase 1 (activates IL1)
Parthanatos is initiated by what? In response to what?
PARP1 in response to severe damage or stress
Entosis is
Detached epithelial cells enguled by autophagy
Chaperone proteins in cytoplasm? In mitochondria?
HSP 70
HSP 60
What happens if unfolded protein response is unsuccessful?
Apoptosis
What allows initiation of autophagy? How?
Inhibition of mTOR; mTOR inhibits ULK1 complex
Where is the isolation membrane derived from in autophagy? What drives its formation?
ER; ULK1 complex (initiation complex)
What does the ULK1 complex activate? What is this complex also called?
Phosphorylates AMBRA1, activating PI3K complex (nucleation complex)
What happens during elongation?
Vesicle forms (autophagosome) marked with LC3
What happens during maturation?
Autophagosome fuses with lysosomes via SNARE-like protein docking to form autophagolysosome
Deletion of what gene increases susceptibility of macrophages to tuberculosis due to defect in autophagy
Atg5
What factors promote autophagy?
BAD, BID (bind BCL-2, preventing binding of Beclin)
Caspase 9
Sirtuins (anti-aging)
p53 in nucleus
What factors inhibit autophagy?
Binding Beclin
BCL-2 (bind Beclin)
FLIP
p53 in cytoplasm
What molecules signal via G-protein coupled receptors?
Eicosanoids, chemokines, some growth factors, thrombin, N-formylmethionyl (bacterial peptides), PTH
What causes Niemann Pick Dz?
Lysosomal Storage Disease- Mutations in enzyme involved in cholesterol trafficking–> cholesterol accumulation in multiple organs
Major trigger and pathway for physiologic myocardial hypertrophy; Two triggers and the pathway for pathologic myocardial hypertrophy?
Mechanical stretch receptors–>PI3K-AKT pathway; Agonists, growth factors–>GPCR
Genes that encode muscle proteins (myocardial hypertrophy)
GATA4, NFAT, MEF2
