ER Flashcards
How do we know that mutated CFTR is still functional?
Mature (glucosylated forms of proteins showed at lower temperatures).
Reversible effect as cells grown at 26C then incubated at 37 showed decrease in mature form with half life of five hours –> turned over.
Growing cells at low temp showed cAMP stimulated Cl- current which decreased as temp increased back up to 37C.
what us the fast response to ER stress?
PERK - phosphorylation of eIF2A
IRE1 - RNAses removes RNA halting translation.
what transcription factors are activated by the intermediate response?
ATF4, XBP1, ATF6 - initiate transcription of chaperones, anti-oxidants, EDEM/proteasome. (EDEM and ER mannosidase I)
how can the cell recover?
PPI dephosphorylates eIF2a
ATF4 slowly induces GADD34 which turns on PPI (unless PERK remains active & keeps phosphorylating eIF2a).
What is ICP34.5 ?
produced by HSV = activator of PP1.
Which viruses produce the following factors; mK3 UL49.5 E3/19k ICP47 US6?
murine gamma virus bovine herpes virus adenovirus HSV cytomegalovirus.
Which chaperones hold together the MCH1 dimer?
Bip, calnexin, ERp57.
How is apoptosis initiated in response to UPR?
IRE1 associates with TRAF2 –> ASK1 activated initiating phosphorylation and activation of JNK promoting apoptosis by phosphorylating and inhibiting Bcl-2 & Xl & by activating Bad & Bim.
What is a target of ATF4?
CHOP = a TF that was shown to increase transcription of Bim during ER stress.
What are the folding affects associated with CF?
Mutant Phe508 on NBD1 surface –> affects interaction with MSD2 and then ability of NBD1 and 2 to dimerise.
What happens to misfiled proteins?
They remain bound to chaperones
They are transported to cytosol and degraded in lysosomes.