Localization and Turnover of Phosphatidylinositol 4,5-Bisphosphate in Caveolin-enriched Membrane Domains

doi:10.1074/jbc.271.43.26453

Localization and Turnover of Phosphatidylinositol 4,5-Bisphosphate in Caveolin-enriched Membrane Domains*

Linda J. Pike^‡ and
Laurieann Casey

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

^‡ 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
. Fax: 314-362-7183.

Abstract

Caveolae are small, plasma membrane invaginations that have been implicated in cell signaling. In A431 cells, approximately half of the total cellular phosphatidylinositol 4,5-bisphosphate (PtdIns 4,5-P₂) was found to be localized in low density, Triton-insoluble membrane domains enriched in caveolin. Treatment of cells with either epidermal growth factor or bradykinin for 5 min at 37°C resulted in approximately a 50% decrease in this caveolar PtdIns 4,5-P₂ with no change in the levels of plasma membrane PtdIns 4,5-P₂. These data suggest that the PtdIns 4,5-P₂ present in cells is largely compartmentalized and that the caveolar PtdIns 4,5-P₂ is subject to hydrolysis by hormone-stimulated phospholipase C. As growth factor receptors, seven transmembrane domain receptors, heterotrimeric G proteins, and the inositol trisphosphate receptor have all been shown to be enriched in caveolae, these findings suggest that both the generation and response to inositol trisphosphate is highly compartmentalized within the cell.

Footnotes

↵* This work was supported by National Institutes of Health Grant PO1 HD20805208A1. 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.
↵¹ The abbreviations used are:

PtdIns 4,5-P₂

phosphatidylinositol 4,5-bisphosphate

PtdIns

phosphatidylinositol

lyso-PtdIns

lysophosphatidylinositol

PtdInsP

phosphatidylinositol monophosphate

DMEM

Dulbecco's modified Eagle's medium

EGF

epidermal growth factor

MES

4-morpholineethanesulfonic acid.
- Received July 22, 1996.
- Revision received September 4, 1996.