test 2, 14 vesicular trafficking Flashcards
What is the best environment for lysosomes?
- acidic with proteolytic cleavage sites
What are lysosomes best used for?
intracellular digestion
What maintains the acidic environment that lysosomes require to operate?
Vacuolar ATPase. Pumps H ions into the lysosomes environment
What are the different stages of lysosome development?
- early endosom
- late endosome
- endolysosome
- lysosome
What methods allow compounds to enter into a lysosome?
- phagocytosis
- endocytosis
- autophagy
- macropinocytosis
What sorts hydrolases to lysosome form the TGN?
- mannose-6-phosphate is required.
2. helps form a clathrin coated vesicle that is delivered to endosome and develops into lysosome
What compound is used to add the M6P to the lysosomal hydrolase?
UDP-GlcNAc, which ultimately will fall off and leave M6P attached
What is Hurler’s disease?
- mutation occurs in the enzyme that degrades glycosaminoglycan chain
What is inclusion cell disease?
- lysosomal hydrolases are absent in multiple cell types, leading do substrate accumulation
What enzyme is responsible for attaching M6P to lysosomal hydrolases?
- GlcNAc phosphotransferases. no phosphorylation means no signal that delivers vesicles to the lysosome.
If GlcNAc is mutated and ineffective, where will compounds be transported if not sent to the lysosome?
- cell surface and secreted into the bloodstream
What is endocytosis?
invagination of the PM that forms an endocytic vesicle of components from outside the cell. Use phagocytosis or pinocytosis
What is receptor-mediated endocytosis?
- selective concentration mechanism of uptake.
2. utilizesmolecules that bind to receptors and accumulate in clathrin-coated pits
What is one example that utilizes receptor-mediated endocytosos? What happens if something in the system were to fail?
- cholesterol
2. atherosclerosis
What are the fates of proteins that have been endocytosed?
- degradation via endolysome
- transcytosis out of the cell
- recycle of transport vesicles
What is the process of phagocytosis?
- performed by macrophages and neutrophils
2. fuse with lysosomes to degrade the ingested material
Phagocytes use exocytosis in what scenario to do what?
- secrete undigested material
By what mechanism are phagocytes activated to perform phagocytosis?
- Ab binds with Ag
- interaction triggers pseudopod formation
- pseudopod engulfs the Ag forming phagosome
What controls and drives the pseudopod formation during phagocytosis?
- actin polymerization and reogranization (structure rearrangement)
- phosphoinositide and Rho GTPases signaling
What is the first step in pinocytosis and what are the outcomes of the process?
- clathrin coated pits start the process
- continuous process in eukaryotes
- ingest small bits of PM
- traps extracellular fluid and solutes in the pits
How are caveolae pits different than the clathrin coated pits?
- enriched with cholesterol and glycosphingolipids and GPI anchored membranes
- invagination occurs due to lipid content
- require dynamin
- unable to fuse with lysosome
What is the process fo forming secretory vesicles?
- proteins aggregate in the TGN
- selected proteins packed into vesicles
- secreted proteins also undergo proteolytic processing
- require clathrin coats that fall away after formation of vesicle
What proteins are required to form the binding components of exocytosis to occur?
- synaptobrevin (v-SNARE)
- syntaxin (t-SNARE)
- SNAP25 (t-SNARE)
What role does synaptotagmin have with exocytosis?
- aids in fusion pore opening
