Anionic Phospholipids Activate ATP-sensitive Potassium Channels

doi:10.1074/jbc.272.9.5388

Anionic Phospholipids Activate ATP-sensitive Potassium Channels*

Zheng Fan^‡ and
Jonathan C. Makielski

From the Department of Medicine, University of Wisconsin, Madison, Wisconsin 53792 and University of Chicago, Chicago, Illinois 60637

^‡ To whom correspondence should be addressed:
Dept. of Medicine, Room 1683, MSC Bldg., 1300 University Ave., Madison, WI 53706.
Tel.: 608-263-2250; Fax: 608-262-4761; E-mail: zfan{at}facstaff.wisc.edu

Abstract

The ATP-sensitive potassium channel (KATP) controls insulin release in pancreatic β-cells and also modulates important functions in other cell types. In this study we report that anionic phospholipids activated KATP in pancreatic β-cells, cardiac myocytes, skeletal muscle cells, and a cloned KATP composed of two subunits (SUR/Kir6.2) stably expressed in a mammalian cell line. The effectiveness was proportional to the number of negative charges on the head group of the anionic phospholipid. Screening negative charges with polyvalent cations antagonized the effect. Enzymatic treatment with phospholipases that reduced charge on the lipids also reduced or eliminated the effect. These results suggest that intact phospholipids with negative charges are the critical requirement for activation of KATP, in distinction from the usual cell signaling pathway through phospholipids that requires cleavage. Mutations of two positively charged amino acid residues at the C terminus of Kir6.2 accelerated loss of channel activity and reduced the activating effects of phospholipids, suggesting involvement of this region in the activation. Metabolism of anionic phospholipids in plasmalemmal membrane may be a novel and general mechanism for regulation of KATP and perhaps other ion channels in the family of inward rectifiers.

Footnotes

↵* This work was supported by a grant-in-aid from the American Heart Association, Wisconsin affiliate (to Z. F.) and grants from the Sprague Foundation and the Oscar Rennebohm Foundation, Inc. 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:

KATP

ATP-sensitive potassium channel

PPI

phosphoinositide

PI(4,5)

P₂, phosphatidylinositol 4,5-bisphosphate

PI(4)P

phosphatidylinositol 4-phosphate

PI

phosphatidylinositol

PS

phosphatidylserine

PC

phosphatidylcholine

PE

phosphatidylethanolamine

IP₃

inositol 1,4,5-triphosphate

DOG

1,2-dioctanoyl glycerol (8:0 DG)

DPG

1,2-dipalmitoyl glycerol (16:0 DG)

PLC-PI

phosphatidylinositol-specific phospholipase C

PLC

phospholipase C

PLA₂

phospholipase A₂

PLD

phospholipase D

AMP-PNP

adenosine 5′-(β,γ-imino)triphosphate

AMP-PCP

adenosine 5′-(β,γ-methylenetriphosphate)

HEK

human embryonic kidney.
- Received December 3, 1996.
- Revision received December 27, 1996.