Hrd1 interaction proteomics - Lipid disequilibrium disrupts ER proteostasis by impairing ERAD substrate glycan trimming and dislocation

Endoplasmic reticulum (ER)-associated degradation (ERAD) mediates the degradation of misfolded and unoligomerized proteins in the early secretory pathway. ERAD substrates are detected and delivered to membrane-embedded dislocation complexes. Following transfer into the cytosol, substrates are rapidly ubiquitinated and targeted to the 26S proteasome for degradation. Hrd1 is a highly conserved, ER-resident E3 ubiquitin-protein ligase that functions in ERAD. In this study, we employed stable isotope labeling with amino acids in cell culture (SILAC) to quantitatively assess the impact of altered lipid homeostasis on the composition of S-tagged Hrd1 complexes affinity purified from HEK293 cells. Although lipid disequilibrium impaired ERAD substrate delivery to Hrd1, the overall composition of the Hrd1 complex was unaffected.