3-hydroxy-3-methylglutaryl-CoA reductase regulatory and degradation machinery (HMGCR-ERAD)

The 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) regulatory and degradation machinery is a complex system in the endoplasmic reticulum (ER) that maintains cholesterol homeostasis by controlling the stability of HMGCR, the rate-limiting enzyme of the mevalonate pathway (NIH, 2023). This machinery utilizes the Endoplasmic Reticulum-Associated Degradation (ERAD) pathway to degrade HMGCR in response to elevated sterol levels, such as cholesterol or lanosterol (UniProt, 2024). The process involves the binding of HMGCR to Insig-1 or Insig-2 proteins, which then recruit E3 ubiquitin ligases like gp78 (AMFR), TRC8 (RNF139), and RNF145 to ubiquitinate the enzyme (PubMed, 2018). Ubiquitinated HMGCR is extracted from the ER membrane by the VCP/p97 ATPase and degraded by the 26S proteasome (Nature, 2022). Dysregulation of this machinery is linked to hypercholesterolemia, cardiovascular disease, and statin resistance in cancer (ResearchGate, 2025). While statins inhibit HMGCR activity, they also cause a compensatory increase in protein levels, making the degradation machinery an attractive target for novel small-molecule degraders like SR-12813 and Cmpd 81 (PubMed, 2023).

Other names

HMGCR degradation pathwayHMG-CoA reductase ERAD machineryInsig-mediated HMGCR degradationHMGCR-Insig-E3 ligase complex

Induction of HMG-CoA reductase degradation via the ERAD pathway or competitive inhibition of HMG-CoA reductase catalytic activity.