Cholesterol Depletion Delocalizes Phosphatidylinositol Bisphosphate and Inhibits Hormone-stimulated Phosphatidylinositol Turnover

doi:10.1074/jbc.273.35.22298

Cholesterol Depletion Delocalizes Phosphatidylinositol Bisphosphate and Inhibits Hormone-stimulated Phosphatidylinositol Turnover*

Linda J. Pike‡ and
Joanne M. Miller

From the Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110

Abstract

Caveolae and detergent-insoluble, glycosphingolipid-enriched domains (DIGs) are cholesterol-enriched membrane domains that have been implicated in signal transduction because a variety of signaling proteins as well as phosphatidylinositol bisphosphate (PtdInsP₂) are compartmentalized in these domains. We report here that depletion of cellular cholesterol leads to the inhibition of epidermal growth factor- and bradykinin-stimulated PtdIns turnover in A431 cells. This is associated with the loss of compartmentalization of epidermal growth factor receptors, G_q, and PtdInsP₂ in the low density membrane domains. Replacement of cellular cholesterol leads to the reorganization of signaling molecules in the low density domains and the reestablishment of hormone-stimulated PtdIns hydrolysis. Oxysterol derivatives show a variable ability to functionally replace the cholesterol in this system. These data are consistent with the hypothesis that localization of signaling proteins and lipids to cholesterol-enriched domains is required for the proper function of hormone-stimulated PtdIns turnover.

Footnotes

↵* The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵‡ To whom correspondence should be addressed: Dept. of Biochemistry and Molecular Biophysics, Washington University School of Medicine, 660 So. Euclid, Box 8231, St. Louis, MO 63110. Tel.: 314-362-9502; Fax: 314-362-7183; E-mail: pike{at}biochem.wustl.edu.
Abbreviations:

DIGs

detergent-insoluble, glycosphingolipid-enriched domains

DMEM

Dulbecco’s modified Eagle’s medium

EGF

epidermal growth factor

MES

4-morpholineethanesulfonic acid

PDGF

platelet-derived growth factor

PtdIns

phosphatidylinositol

PtdInsP

phosphatidylinositol monophosphate

PtdInsP₂

phosphatidylinositol bisphosphate.
- Received April 13, 1998.
- Revision received June 6, 1998.
The American Society for Biochemistry and Molecular Biology, Inc.