LEcture 13 Flashcards
LDL Particles?
Whole cholesterol esters and free cholesterol that are surrounded by a phospholipid layer and then that whole thing is surrounded by a large protein called Apolipoprotein b.
Retromer?
Membrane bound organelle/vesicle coming from the endosome
-long tubules
Retrograde traffic?
From the endosome to the PM
or From the endosome to the trans-golgi
Initiator of retromer formation?
Rab5-GTP or Rab7-GTP
Adaptor Proteins for retromer formation?
Vps26/29/35
Coat protein for retromer formation?
Sorting Nexins
How does the cell differentiate between the two fates of a receptor?
Mono-ubiquitination
Tails of receptors stick into the cytosol from the CCV what happens when the receptor is targeted for degradation?
Multivesicular bodies. Vesicles bud off from the endosome containing the receptor and are endocytosed
T/F: MVB is the sign of a receptor destined for degradation
True
ESCRT complex?
Forms the multivesicular bodies
Only budding that occurs away from the cytosolic surface?
Multivesicular budding
Lysosome?
Membrane enclosed sac full of hydrolases
-Only actie in low pH 5
Hydrolases examples?
Nucleases, Proteases, Lipases
Low pH of lysosomes is maintained by?
ATP-dependent proton pump
Four pathways of lysosomal degradation?
- Endocytosis
- Phagocytosis
- Macropinocytosis
- Autophagy
Endocytosis
-Bringing things from the outside of the cell through the endosomes and to the lysosome for breaking down
-Uptake of macromolecules at the PM often via a receptor and also uptake of macromolecules in the extracellular fluid
Phagocytosis?
-No receptors, adaptors or vesicles
-Engulfment of large molecules(bacteria)
-Cytoskeleton in the PM projects out and surrounds the cargo forms a phagosome
Macropinocytosis?
- Non-specific uptake of fluids, solutes & particles attached to the PM
-Cell needs a particular nutrient
Micropinocytosis?
Cell is sampling fluid around itself
Autophagy?
-Self-eating
-Large scale digestion of cytosol, membranes, organelles, aggregates, etc.
Selective Autophagy?
cell recognizing something in the system that it must get rid of
Autophagy and backed up ubiquitination protease system?
Ubiquitinated proteins are normally broken down by the proteasome but if that system is very overwhelmed not all of the ubiquitinated proteins will make it into the proteasome and they will start aggregating into large aggregates at this point autophagy may be used
Non-selective autophagy?
-Occurs when the cell is starving
-It will start taking up random things in the cytoplasm and break them down just to get nutrients to survive in a starvation situation
Macroautophagy?
- Nucleation event: small vesicles coalesce in the cytoplasm and form an initial membranous structure called a phagophore
- Phagophore grows by fusion with additional vesicles to form an autophagosome
- Autophagosome will bind to the lysosome and degradation occurs
ATG8
recognizes the receptor which is bound to the cargo that needs to be degraded
