Understanding and harnessing quality control in the secretory pathway

The National Institute of General Medical Sciences awarded the Regents of the University of Michigan $159,560 on December 31, 2026, under the Biomedical Research and Research Training program (CFDA 93.859) to develop and execute a high-throughput screening platform identifying endoplasmic reticulum-associated degradation (ERAD) degrons—short amino acid sequences that signal misfolded proteins for removal and degradation. The research addresses how cells recognize and selectively degrade misfolded proteins while preserving properly folded ones, with applications to metabolic disorders, neurodegeneration, and cancer. Performance occurs at the University of Michigan in Ann Arbor, Michigan, with completion targeted for June 30, 2029.

Abstract

The endoplasmic reticulum (ER) is an expansive organelle that is the site of a wide array of essential cellular processes. Classically, this organelle is appreciated for its role in protein biogenesis, serving as the entry point into the secretory pathway and endomembrane system. Accordingly, the vast majority of soluble secretory proteins, as well as transmembrane proteins, are first synthesized at the ER. Underscoring the substantial role of the ER in protein biogenesis, IT is estimated that roughly one-third of the entire proteome is made at this site. Because of this significant protein folding burden within the ER lumen, cells have adapted elaborate mechanisms for removal of misfolded proteins that serve to prevent accumulation of these toxic protein species. One major route for removal is through endoplasmic reticulum-associated degradation (erad). The erad system specifically recognizes misfolded proteins and delivers them into the cytosol where they are tagged with ubiquitin, marking them for degradation by the proteasome. Disruption of ER proteostasis is a hallmark of numerous diseases, including metabolic disorders, neurodegeneration, and cancer. Accordingly, the erad system is highly conserved and essential for viability. Erad knockout is lethal in mice, and mutations in the erad system are pathogenic to humans. How erad recognizes misfolded proteins and ignores folded proteins is poorly understood. Current evidence suggests that selectivity can be conferred by short amino acid sequences, termed "degrons," which are defined as the minimal motif within a protein that is required for recognition by degradation machinery. My preliminary results have uncovered novel erad degrons that are sufficient to drive an ER-localized-protein substrate into the erad pathway. In this proposal, i have developed a high-throughput screening platform to identify erad degrons from human proteins. I will use this system to identify human erad degrons at a proteome-wide scale, and define the mechanics of substrate recognition that govern the high fidelity and diversity of erad substrate selection. Additionally, i have developed a targeted protein degradation technology that utilizes erad degrons to selectively degrade pathogenic proteins that are made in the ER. To achieve these aims, i will use high-scale variant libraries and DNA sequencing technology to uncover degron sequences that the mammalian erad system recognizes and use these substrates to mechanistically interrogate mammalian erad. Additionally, i will use cell biology and biochemical techniques within mammalian tissue culture systems to potentiate targeted protein degradation from within the endomembrane system. Successful completion of this proposal would unlock the ability to selectively degrade the one-third of the proteome that fluxes through secretory pathway and illuminate how the system that governs the fidelity of this pathway functions.