Endocytosis

Question 1

How to create an Endocytosis vesicle starting from PIP3

Answer 1

PIP3 becomes Pip2 from enzyme PTEN. Pip2 recruits and activates Arp2. Arp2 then binds cargo receptors. Clathrin recruited, binds to Arp2. Dynamin required to complete vesicle fission.

Question 2

When are recycled receptors returned to the membrane and what is the signal for recycling vs degradation?

Answer 2

It is returned before the formation of the multivesicular body. Recycled=phosphorylated.
Degraded = ubiquitinated.

Question 3

Constitutive vs stimulated Endocytosis

Answer 3

Constitutive: does not require a ligand to bind. Example:LDL
Stimulated: requires ligand to bind receptor. Example: EGF

Question 4

What protein helps form multivesicular bodies?

Answer 4

Escort Proteins (ESCRT)

Question 5

Four major steps of lysosomes formation

Answer 5

1. Multivesicular body formation
2. Glycosylation of inner membrane (presents degradation of endosome membrane)
3. Acidification of endosome
4. Fusion with lysosome