Zaidi: Trafficking 2 Flashcards
Antibody interaction in phagocytosis
Antibodies bind to microbe, Fc chain recognized by Fc receptor on macrophage/neutrophil
Binding triggers formation of pseudopod which engulfs particle and forms phagosome
Regulated secretory pathway
Triggered by signals
Blockage of cholesterol uptake pathway results in
Atherosclerosis
Constitutive secretory pathway
Operates continuously
Hurlers disease
Mutation in the enzyme required to break down glycosaminoglycan chains
GlcNAc phosphotransferase
Transfers GlcNAc-Pi to mannose to create GlcNAc-M6P
GlcNAc is then removed and you have M6P
Phagocytes include
WBCs such as macrophages and neutrophils
Storage of receptor proteins in recycling endosomes
Receptor proteins such as glucose transporters can be stored in endosomes.
Cell recieves signal that it needs more glucose when insulin binds insulin receptor
More glucose transporters are then transported to membrane from endosomes
Proteins destined for secretion are packaged where and involves what
Into secretory vesicles in the TGN
Involves selective aggregation/clumping of proteins
Lysosomal storage disease
Genetic defects in lysosomal hydrolases
Accumulation of undigested material in lysosomes
Vesicle coat involved in pinocytosis
Clathrin coated pits
Proteins are concentrated into vesicle by
Retrieval of other proteins that go back to TGN and ER
Pseudopod formation driven by and controlled by
Driven by localized actin polymerization and reorganization
Controlled by Rho GTPases and PI signaling
LDL receptors have binding site for
Clathrin, to ensure the vesicle forms around the LDL receptors
Membrane protein/hydrolases transport to lysosomes
Co-translationally transported into RER and then transported via golgi complex to TGN
TGN buds off into endosomes which develop into lysosomes
Phagocytosis
Large particles ingested by phagosomes
What happens to undigested material
It is secreted through exocytosis
Lysosomal hydrolases have what sorting signal
Mannose-6-Phosphate is attached to them in the Cis golgi network
M6P receptors in TGN recognize the sugar
Vacuolar ATPase
Pumps H+ into lysosomes to maintain acidid pH and drive transport of small metabolites
Caveolae
Flask-shaped invaginations in PM, enriched in cholesterol and glycosphingolipids
Major structural protein is Caveolin
TGN promotes
Proteolytic processing of the secretory proteins- activation mechanism
Inclusion cell disease
All of the lysosomal hydrolases are missing in many cell types. Undigested substrates accumulate as “inclusions”
Defective or missing GlcNAc phosphotransferase
Lysosomal hydrolases with mannose are never phosphorylated to create M6P.
Therefore, hydrolases do not get delivered to lysosomes, they are carried to cell surface and secreted
Caveolae invaginate into membrane by virtue of, they pinch off from PM by
Lipid composition, NOT the clathrin coat
Pinch of PM by dynamin-form caveosome
These DO NOT connect with lysosomes
Exocytosis route
Transport vesicles move from TGN to PM
What happens to LDL receptors after they successfully bring LDL into endosomes
They are recycled back to the plasma membrane
What type of vesicles bud off from TGN to create endosomes
Clathrin-coated vesicles
Receptor-mediated endocytosis
Imports select macromolecules from outside cell
They bind receptors on membrane and accumulate in clathrin coated pits
Example of this mechanism is cholesterol uptake
Endocytosis
Uptake of macromolecules from exterior across plasma membrane
Pinocytosis
Small particles ingested by pinocytic vesicles
Lysosomes are derived from and contain
Late endosomes
Contain hydrolytic enzymes
