A synonymous variant in scavenger receptor, class B, type I gene is associated with lower SR-BI protein expression and function.
OBJECTIVE
A synonymous variant within scavenger receptor class B type I gene (SCARB1), exon 8 rs5888, has been associated with altered lipid levels and cardiovascular risk in humans. The objective was to determine if rs5888 decreased SR-BI protein expression and function in vitro.


METHODS
SR-BI RNA secondary structure, turnover, polysomal distribution and protein expression were examined in COS cells transfected with wild-type or rs5888-SR-BI plasmids by selective 2'-hydroxyl acylation and primer extension assays, actinomycin D inhibition, polysomal profiling, and western blotting. SR-BI function in murine macrophages stably expressing wild-type or rs5888-SR-BI was assessed by measuring the specific cell association of (125)I,(3)H-cholesteryl ester (CE) radiolabeled HDL.


RESULTS
Rs5888 changed RNA secondary structure and led to marked differences in the polysomal profiles compared with wild-type transcript (p<0.02). As compared to wild-type cells, COS cells expressing rs5888 had significantly lower SR-BI protein expression (p<0.04), but no difference in total RNA transcript levels. There were no differences in SR-BI RNA turnover in murine macrophages, whereas specific cell association of (125)I (p<0.0001) or (3)H-CE (p<0.00001) was significantly lower in rs5888 cells.


CONCLUSIONS
The rs5888 variant affected SR-BI RNA secondary structure, protein translation, and was significantly associated with reduced SR-BI protein expression and function in vitro.
Constantineau
Jason
J
Department of Medicine, Division of Endocrinology and Metabolism, The Johns Hopkins University School of Medicine, Baltimore, MD 21224, United States.
Greason
Erin
E
West
Michael
M
Filbin
Megan
M
Kieft
Jeffrey S
JS
Carletti
Martha Z
MZ
Christenson
Lane K
LK
Rodriguez
Annabelle
A
D005091:Exons; D006801:Humans; D008264:Macrophages / Q000737:chemistry; D020641:Polymorphism, Single Nucleotide; D012313:RNA / Q000737:chemistry; D051122:Scavenger Receptors, Class B / Q000032:analysis* / Q000235:genetics* / Q000502:physiology; D014158:Transcription, Genetic
C495124:SCARB1 protein, human; D051122:Scavenger Receptors, Class B; D012313:RNA