Functional characterization of newly-discovered mutations in human SR-BI. PLoS One 2012;7(9):e45660
Date
10/03/2012Pubmed ID
23029167Pubmed Central ID
PMC3448639DOI
10.1371/journal.pone.0045660Scopus ID
2-s2.0-84866661659 (requires institutional sign-in at Scopus site) 46 CitationsAbstract
In rodents, SR-BI has been firmly established as a physiologically relevant HDL receptor that mediates removal of HDL-cholesteryl esters (CE). However, its role in human lipoprotein metabolism is less defined. Recently, two unique point mutations in human SR-BI - S112F or T175A - were identified in subjects with high HDL-cholesterol (HDL-C) levels. We hypothesized that mutation of these conserved residues would compromise the cholesterol-transport functions of SR-BI. To test this hypothesis, S112F- and T175A-SR-BI were generated by site-directed mutagenesis. Cell surface expression was confirmed for both mutant receptors in COS-7 cells upon transient transfection, albeit at lower levels for T175A-SR-BI. Both mutant receptors displayed defective HDL binding, selective uptake of HDL-CE and release of free cholesterol (FC) from cells to HDL. Mutant receptors were also unable to re-organize plasma membrane pools of FC. While these impaired functions were independent of receptor oligomerization, inability of T175A-SR-BI to mediate cholesterol-transport functions could be related to altered N-linked glycosylation status. In conclusion, high HDL-C levels observed in carriers of S112F- or T175A-SR-BI mutant receptors are consistent with the inability of these SR-BI receptors to mediate efficient selective uptake of HDL-CE, and suggest that increased plasma HDL concentrations in these settings may not be associated with lower risk of cardiovascular disease.
Author List
Chadwick AC, Sahoo DAuthor
Daisy Sahoo PhD Dean, Professor in the Medicine department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
AnimalsCD36 Antigens
COS Cells
Glycosylation
Humans
Mutagenesis, Site-Directed
Mutation
