TY - JOUR
T1 - Differential use of E2 ubiquitin conjugating enzymes for regulated degradation of the rate-limiting enzymes HMGCR and SQLE in cholesterol biosynthesis
AU - Tan, Josephine M. E.
AU - Cook, Emma C. L.
AU - van den Berg, Marlene
AU - Scheij, Saskia
AU - Zelcer, Noam
AU - Loregger, Anke
PY - 2019
Y1 - 2019
N2 - Background and aims: Cholesterol is an essential lipid for cellular function and membrane integrity, and hence its cellular levels and distribution must be tightly regulated. Biosynthesis of cholesterol is ramped when its cellular levels are low. Herein, the ER-resident and rate-limiting enzymes 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) and squalene monooxygenase (SQLE) play a prominent role. We have recently reported that MARCH6, an E3 ubiquitin ligase, specifically promotes cholesterol-stimulated ubiquitylation and subsequent proteasomal degradation of SQLE, but not of HMGCR. To further delineate how post-translational regulation of SQLE and HMGCR is differentially achieved, we hypothesized that their sterol-dependent degradation machinery makes use of distinct E2 ubiquitin conjugating enzymes. Methods: To study this possibility, we therefore used a CRISPR/Cas9-based approach to screen for ER-associated degradation (ERAD)-associated E2 enzymes that are essential for MARCH6-dependent degradation of SQLE. Results: We report here the identification of UBE2J2 as the primary E2 ubiquitin conjugating enzyme essential for this process in mammalian cells, in contrast to UBE2G2, which is essential for sterol-stimulated degradation of HMGCR. We demonstrate that ablating UBE2J2 disturbs cholesterol-accelerated SQLE degradation in multiple human cell types, including cells of hepatic origin, and that the ability of UBE2J2 to support SQLE degradation critically depends on its enzymatic activity. Conclusions: Our findings establish UBE2J2 as an important partner of MARCH6 in cholesterol-stimulated degradation of SQLE, thereby contributing to the complex regulation of cellular cholesterol homeostasis.
AB - Background and aims: Cholesterol is an essential lipid for cellular function and membrane integrity, and hence its cellular levels and distribution must be tightly regulated. Biosynthesis of cholesterol is ramped when its cellular levels are low. Herein, the ER-resident and rate-limiting enzymes 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) and squalene monooxygenase (SQLE) play a prominent role. We have recently reported that MARCH6, an E3 ubiquitin ligase, specifically promotes cholesterol-stimulated ubiquitylation and subsequent proteasomal degradation of SQLE, but not of HMGCR. To further delineate how post-translational regulation of SQLE and HMGCR is differentially achieved, we hypothesized that their sterol-dependent degradation machinery makes use of distinct E2 ubiquitin conjugating enzymes. Methods: To study this possibility, we therefore used a CRISPR/Cas9-based approach to screen for ER-associated degradation (ERAD)-associated E2 enzymes that are essential for MARCH6-dependent degradation of SQLE. Results: We report here the identification of UBE2J2 as the primary E2 ubiquitin conjugating enzyme essential for this process in mammalian cells, in contrast to UBE2G2, which is essential for sterol-stimulated degradation of HMGCR. We demonstrate that ablating UBE2J2 disturbs cholesterol-accelerated SQLE degradation in multiple human cell types, including cells of hepatic origin, and that the ability of UBE2J2 to support SQLE degradation critically depends on its enzymatic activity. Conclusions: Our findings establish UBE2J2 as an important partner of MARCH6 in cholesterol-stimulated degradation of SQLE, thereby contributing to the complex regulation of cellular cholesterol homeostasis.
UR - https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85059899532&origin=inward
UR - https://www.ncbi.nlm.nih.gov/pubmed/30658189
U2 - https://doi.org/10.1016/j.atherosclerosis.2018.12.008
DO - https://doi.org/10.1016/j.atherosclerosis.2018.12.008
M3 - Article
C2 - 30658189
SN - 0021-9150
VL - 281
SP - 137
EP - 142
JO - Atherosclerosis
JF - Atherosclerosis
ER -