Abstract 17: SURP and G Patch Domain Containing 1 is a Novel Regulator of Cholesterol Metabolism
rs10401969 tags a large GWAS-identified locus associated with coronary artery disease (CAD) and plasma LDL cholesterol. This locus contains over a dozen genes, as well as a nonsynonymous SNP in TM6SF2. Recently, several studies have shown that TM6SF2 impacts lipid metabolism, and concluded that it is a causative gene within the locus. However, it is possible that one or more of the other genes at this locus may also contribute to CAD risk. SURP and G patch domain containing 1 (SUGP1) is a putative splicing factor, and we have previously reported that cholesterol genes can be coordinately regulated by alternative splicing. Since rs10401969 is contained within intron 8 of SUGP1, we hypothesized that SUGP1 may contribute to the relationship between rs10401969 and plasma LDLC. Western blot analysis of lymphoblastoid cell lines (n=48) revealed that SUGP1 protein levels differed by rs10401969 genotype. In HepG2 and Huh7 cells transfected with a SUGP1 mini-gene construct, we found that rs10401969 induces SUGP1 exon 8 skipping, creating a SUGP1 transcript that is subject to nonsense-mediated decay. Through EMSAs, we established that rs10401969 disrupted binding of HNRNPA1, a well-known splicing factor of SUGP1 RNA. To establish the physiological effects of SUGP1, we overexpressed Sugp1 by tail vein delivery into CD1 male mice (n=10), and after 1 and 4-weeks, plasma cholesterol levels were increased 20% and 50%, respectively, compared to controls. In HepG2 and Huh7 cells, we found that SUGP1 targets 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), which encodes the rate-limiting step of cholesterol biosynthesis. SUGP1 knock-down stimulated alternative splicing of HMGCR and decreased transcript stability, resulting in reduced HMGCR enzyme activity, cholesterol synthesis and increased LDL uptake. These findings are consistent with the increase in plasma cholesterol observed after Sugp1 overexpression in vivo. In summary, these results support a role for SUGP1 as a multi-functional RNA binding protein that regulates cholesterol metabolism and suggest that this effect contributes to the GWAS association of rs10401969 with CAD.
Author Disclosures: M.W. Medina: None. C. Yu: None. M.J. Kim: None. E. Theusch: None. D. Naidoo: None. K. Stevens: None. Y. Kuang: None.
- © 2015 by American Heart Association, Inc.