Fan Z, Makielski J C
Department of Medicine, University of Wisconsin, Madison, Wisconsin 53792, USA.
J Biol Chem. 1997 Feb 28;272(9):5388-95. doi: 10.1074/jbc.272.9.5388.
The ATP-sensitive potassium channel (KATP) controls insulin release in pancreatic beta-cells and also modulates important functions in other cell types. In this study we report that anionic phospholipids activated KATP in pancreatic beta-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.
ATP敏感性钾通道（KATP）控制胰腺β细胞中的胰岛素释放，并且还调节其他细胞类型中的重要功能。在本研究中，我们报告阴离子磷脂在胰腺β细胞、心肌细胞、骨骼肌细胞以及由两个亚基（SUR/Kir6.2）组成的克隆KATP（稳定表达于哺乳动物细胞系）中激活了KATP。其有效性与阴离子磷脂头部基团上的负电荷数量成正比。用多价阳离子筛选负电荷可拮抗该效应。用磷脂酶进行酶处理以减少脂质上的电荷，也会降低或消除该效应。这些结果表明，带有负电荷的完整磷脂是激活KATP的关键要求，这与通常通过需要裂解的磷脂的细胞信号传导途径不同。Kir6.2 C末端的两个带正电荷氨基酸残基的突变加速了通道活性的丧失，并降低了磷脂的激活作用，表明该区域参与了激活过程。质膜中阴离子磷脂的代谢可能是调节KATP以及内向整流器家族中其他离子通道的一种新的普遍机制。
