Membrane lipid sensing during ERAD: coupling lipid composition to proteostatic fate.

The endoplasmic reticulum (ER) membrane is both the central site of cellular lipid synthesis and the platform on which ER-associated degradation (ERAD) selects membrane proteins for ubiquitination and proteasomal destruction. ERAD shapes ER lipid composition by degrading biosynthetic enzymes and regulators of lipid metabolism, while the lipid environment in turn modulates each step of the pathway. In this review, we apply biophysical concepts of membrane protein dynamics to explain how changes in membrane composition shift conformational equilibria and bias proteostatic fate. We distinguish three modes through which lipid information reaches ERAD: substrate-intrinsic sensing, adaptor-mediated coupling, and lipid sensitivity of the ubiquitination machinery itself. These perspectives reframe ERAD as a lipid-responsive pathway integrating membrane composition with selective protein turnover.