Title: Should I stay or should I go? Investigating the fate of misfolded membrane proteins in the mammalian ER
Abstract:
One-third of all proteins enter the secretory pathway at the endoplasmic reticulum (ER) where they fold to adopt functional conformations. While ER chaperones stabilize proteins during folding and retain soluble misfolded proteins in the ER, membrane proteins present unique challenges and—at least in yeast—can be retained in the ER as a result of aggregation and ubiquitination. Notably, misfolded membrane protein retention is essential for cell health since these toxic substrates can be destroyed by ER-associated degradation (ERAD). Yet, some of these proteins escape the ER. To date, the factors dictating these fates in mammals remain obscure. We previously utilized a model substrate, SZ*, that can be targeted to both fates in yeast. SZ* retention required a ubiquitin-binding protein, Ubx2, but whether the human homologues of Ubx2 play similar roles is unclear. Therefore, I created a mammalian cell line with stable, inducible SZ* expression and found that SZ* is targeted for ERAD. This degradation is slowed by combined knockdown of two Ubx2 homologs. To monitor ER retention, I am developing a fluorescence reporter so the fate of SZ* can be quantified and additional retention factors identified from knockdown libraries.The contributions of factors affecting SZ* retention and ERAD will then be examined for effects on a disease-associated mutant of the cystic fibrosis transmembrane conductance regulator (CFTR). Together, defining the mechanisms of ER retention for misfolded membrane proteins will detail the cellular decisions regulating the severity of human diseases.
Brodsky Lab
Friday, January 12th, 2023
12:00PM
Langley A219B