Membrane Trafficking Flashcards
Which Rans are found in certain compartments?
Rab-5 on endosomal membranes.
Rab-7 on late endosomal membranes
Rab 4 and 11 important for cargo recycling back to PM.
what differs between lipid uptake and iron homeostasis?
L –> LDL destroyed (LDL-R recycled)
I –> Receptor and Tf (soluble iron carrying protein) recycled back to PM to pick up more iron.
What are lysosomes and what two models contents transfer?
storage granules for mature lysosomal enzymes - periodically fuse with late endosomes –> compartment for degradation (no mannose 6 phosphate receptors!!).
Proteolytic & acidic organelles.
Kissing = continuous cycle of transient interactions between LEs and lysosomes.
Direct fusion = of endosome and lysosome to form hybrid organelle.
What consensus has been reached regarding transfer of material from late endosomes to lysosome?
HYBRID organelle formed by heterotypic fusion between late endosome and lysosome.
full complement of lysosomal enzymes but SOME mannose 6 phosphate receptors.
Lysosome reformation requires retrieval of some membrane proteins by vesicular traffic.
How do Salmonella Enterica evade lysosomes?
Produces PIP phsphatases which change the [] of PIPs in phagocyte membrane –> retards phagosome maturation.
How does listeria monocytogenes escape the phagosome?
secretes pore forming toxin listeriolysin O –> slows maturation of phagosomal compartment by altering vacuolar pH and calcium []. Gives bacteria time to escape.
What is the structure of adaptors in clathrin mediated endocytosis?
Link cargo to clathrin 4 subunits - Gamma, Alpha, Delta or Eta - Mew (binds sorting sequences in vesicle cargo proteins) - Sigma - Beta AP-2 important for PM internalisation AP-1 for TGN exit.
