Faculty Collaboration Database

Tryptophan 415 Is Critical for the Cholesterol Transport Functions of Scavenger Receptor BI. Biochemistry 2016 Jan 12;55(1):103-13

Date

12/15/2015

Pubmed ID

26652912

Pubmed Central ID

PMC5428993

DOI

10.1021/acs.biochem.5b00804

Scopus ID

2-s2.0-84954457161 (requires institutional sign-in at Scopus site)   11 Citations

Abstract

High density lipoproteins (HDL) are anti-atherogenic particles, primarily due to their role in the reverse cholesterol transport pathway whereby HDL delivers cholesteryl esters (CE) to the liver for excretion upon interaction with its receptor, scavenger receptor BI (SR-BI). We designed experiments to test the hypothesis that one or more of the eight highly conserved tryptophan (Trp; W) residues in SR-BI are critical for mediating function. We created a series of Trp-to-phenylalanine (Phe, F) mutant receptors, as well as Trp-less SR-BI (ΔW-SR-BI), and assessed their ability to mediate cholesterol transport. Wild-type (WT) or mutant SR-BI receptors were transiently expressed in COS-7 cells, and cell surface expression was confirmed. Next, we showed that Trp-less- and W415F-SR-BI had significantly decreased abilities to bind HDL and promote selective uptake of HDL-CE, albeit with higher selective uptake efficiency as compared to WT-SR-BI. Interestingly, only Trp-less-, but not W415F-SR-BI, showed an impaired ability to mediate efflux of free cholesterol (FC). Furthermore, both W415F- and Trp-less-SR-BI were unable to reorganize plasma membrane pools of FC based on lack of sensitivity to exogenous cholesterol oxidase. Restoration of Trp 415 into the Trp-less-SR-BI background was unable to rescue Trp-less-SR-BI's impaired functions, suggesting that Trp 415 is critical, but not sufficient for full receptor function. Furthermore, with the exception of Trp 262, restoration of individual extracellular Trp residues, in combination with Trp 415, into the Trp-less-SR-BI background partially rescued SR-BI function, indicating that Trp 415 must be present in combination with other Trp residues for proper cholesterol transport functions.

Author List

Holme RL, Miller JJ, Nicholson K, Sahoo D

Author

Daisy Sahoo PhD Dean, Professor in the Medicine department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Animals
Biological Transport
COS Cells
Cholesterol
Lipoproteins, HDL
Models, Molecular
Mutagenesis, Site-Directed
Mutation
Protein Binding
Protein Multimerization
Scavenger Receptors, Class B
Tryptophan