Endocytosis

Question 1

What is clathrin coat structure?

Answer 1

3 heavy 3 light chains, cage-like

Question 2

What are the four different adaptor proteins (one is most important) and what is their common structure?

Answer 2

AP1=TGN and endosomes AP2=main plasma membrane AP AP3=endosomes/tgn AP4= all have 4 polypeps..heterotetrameric w membrane association base core, hinge for clathrin, and accessory protein appendage

Question 3

How are cells recognized to endocytose? 2 ways

Answer 3

Either constitutively or signal on cargo molecule that adaptors recognize (ligand induced uptake)

Question 4

What are the steps in coat assembly to release?

Answer 4

1. cargo molecule (has sorting signal in cytosolic domain) + transmembrane receptor
2. adaptor to to receptor/cargo
3. adaptor and co to clathrin
4. buds off w help of dynamin ring squeeze
5. loss of cathrin and adaptor= naked transport vesicle

Question 6

after entering through CCV when/where are LDL or Transferin receptors recycled from?

Answer 6

sorting endosome sends receptors back to plasma membrane for recycling

Question 7

After LDLR and Transferrin receptors enter early lysosomes what are the TR recycled with? Hint: not iron..

Answer 7

apo-tranferrins

Question 8

Two are the two defects with the LDLR that can cause hypercholesteremia?

Answer 8

defective receptor/clathrin binding site=familial cholest.

defective ARH (adaptor protein)=autosomal recessive cholest.

Question 9

which proteins are the cholesterol transporters around the cell?

Answer 9

npc 1 and 2

Question 10

What is a protein that targets LDLR for degradation in the lysosome rather than recycling? what is it secreted by?

Answer 10

PCSK9 secreted by liver

Question 11

Name which of these is NOT constitutitvely uptaken… LDL Trasferrin EGF

Answer 11

EGF. ligand induced endocytosis

Question 12

Explain the pathway of degradation for EGFR? whats the special complex in endosome that passes it down?

Answer 12

UBQ puts on tails so not recycled> ESCRT passes them down thru endosome until they bud off to go to lysosome

Question 13

How do insulin receptors/binding make more glucose enter the cell?

Answer 13

Insulin binding signals GLUT4 receptors stored in endosomes to go to the surface to induce more glucose uptake

Question 14

CCV endocytosis is what kind of -cytosis?

Answer 14

PINNOcytosis

Question 15

How does the cell engulf bacteria or antigens coated in antibodies?

Answer 15

Fc receptors bind to antigens and then signal casacade induces actin to encircle

Question 16

How can bacteria enter and evade desctruction? what are the 2 mechs for invasion

Answer 16

trigger (just binding of bacteria) and zipper (via adhesin secreted by bacteria)

Question 17

Once pathogen enters what are the 3 choices it has?

Answer 17

1. escape endosome
2. prevent fusion w lysosmes after endosome
3. stay in phagolysosome post fusion w lysosome

Question 18

How does anthrax infect?

Answer 18

binds w its B subunit that forms a ring, A eventually joins, then pH causes it to form a pore in endosome so i can escape degradation

Question 19

Which network do viruses exploit? how about Ebola?

Answer 19

endolytic. Use pH to escape endosomes/lysosomes at various times depending upon what virus it is.

Ebola GP (viral glycoprotein) binds NPC1 to escape lysosome