Cholesterol binding, efflux, and a PDZ-interacting domain of scavenger receptor-BI mediate HDL-initiated signaling

Chatchawin Assanasen, Chieko Mineo, Divya Seetharam, Ivan S. Yuhanna, Yves L. Marcel, Margery A. Connelly, David L. Williams, Margarita De La Llera-Moya, Philip W. Shaul, David L. Silver

Research output: Contribution to journalArticle

122 Scopus citations

Abstract

The binding of HDL to scavenger receptor-BI (SR-BI) mediates cholesterol movement. HDL also induces multiple cellular signals, which in endothelium occur through SR-BI and converge to activate eNOS. To determine the molecular basis of a signaling event induced by HDL, we examined the proximal mechanisms in HDL activation of eNOS. In endothelial cells, HDL and methyl-β-cyclodextrin caused comparable eNOS activation, whereas cholesterol-loaded methyl-β-cyclodextrin had no effect. Phosphatidylcholine-loaded HDL caused greater stimulation than native HDL, and blocking antibody against SR-BI, which prevents cholesterol efflux, prevented eNOS activation. In a reconstitution model in COS-M6 cells, wild-type SR-BI mediated eNOS activation by both HDL and small unilamellar vesicles (SUVs), whereas the SR-BI mutant AVI, which is incapable of efflux to SUV, transmitted signal by only HDL. In addition, eNOS activation by methyl-β-cyclodextrin was SR-BI dependent. Studies of mutant and chimeric class B scavenger receptors revealed that the C-terminal cytoplasmic PDZ-interacting domain and the C-terminal transmembrane domains of SR-BI are both necessary for HDL signaling. Furthermore, we demonstrated direct binding of cholesterol to the C-terminal transmembrane domain using a photoactivated derivative of cholesterol. Thus, HDL signaling requires cholesterol binding and efflux and C-terminal domains of SR-BI, and SR-BI serves as a cholesterol sensor on the plasma membrane.

Original languageEnglish (US)
Pages (from-to)969-977
Number of pages9
JournalJournal of Clinical Investigation
Volume115
Issue number4
DOIs
StatePublished - Apr 2005

ASJC Scopus subject areas

  • Medicine(all)

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    Assanasen, C., Mineo, C., Seetharam, D., Yuhanna, I. S., Marcel, Y. L., Connelly, M. A., Williams, D. L., De La Llera-Moya, M., Shaul, P. W., & Silver, D. L. (2005). Cholesterol binding, efflux, and a PDZ-interacting domain of scavenger receptor-BI mediate HDL-initiated signaling. Journal of Clinical Investigation, 115(4), 969-977. https://doi.org/10.1172/JCI23858