L6: Protein turnover and autophagy part 2

Question 1

LC3 1 and 2

Answer 1

LC31 needs the attachment of lipid side chains to be inserted in the membranes. To attach it becomes LC32 to be inserted involving ATG (a complex) and binds to linker proteins p62 or 1 and they in turn bind to ubiqutin chains.

Question 2

lipidation

Answer 2

Lipidation of LC3-I to LC3-II is taken as a readout for autophagic
activity

Question 3

where does assembly of the autophagosome start

Answer 3

Assembly of an autophagosome starts at the phagophore (derived
from ER or Golgi) and is a kinase-regulated process

Question 4

how to visualise autophagy

Answer 4

use rapamycin that activates phagophore formation. Stimulated autophagy.
another way using bafilomycin that prevents fushion of the autophagosome with the lyososme and arrest autophagy and see accumulation of intermediate steps.

Question 5

types of autophagy

Answer 5

Selective autophagy:
p62 and Nbr1 interaction with LC3-II and poly-ubiquitylated substrate
proteins; encapsulation into double-membraned autophagosome
Non-specific autophagy:
LC3-II association with macromolecular complexes and cellular organelles
(e.g. mitochondria); encapsulation into double-membraned
autophagosome

Question 6

fusing autophagosome with lysosome

Answer 6

SNAREs. Lysosome, single membrane organelle and very acific environment for enzymes to chop peptides to amino acids. SNARE complexes mediate the fusion with autophagosome
.

Question 7

knockout autophagy in muscle

Answer 7

> get myopathy (muscle atrophy, accumulation of abnormal
mitochondria, sarcomere disorganisation)
skeletal muscle highly specialised and lots of mitochondria. accumulation of damaged mitochondria.