Pike L J, Casey L
Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
J Biol Chem. 1996 Oct 25;271(43):26453-6. doi: 10.1074/jbc.271.43.26453.
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 degrees 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.
小窝是质膜的小内陷，与细胞信号传导有关。在A431细胞中，发现细胞总磷脂酰肌醇4,5-二磷酸（PtdIns 4,5-P2）的大约一半定位于富含小窝蛋白的低密度、不溶于Triton的膜结构域中。在37℃用表皮生长因子或缓激肽处理细胞5分钟，导致这种小窝PtdIns 4,5-P2减少约50%，而质膜PtdIns 4,5-P2水平没有变化。这些数据表明，细胞中存在的PtdIns 4,5-P2在很大程度上是分隔存在的，并且小窝PtdIns 4,5-P2会受到激素刺激的磷脂酶C的水解作用。由于生长因子受体、七跨膜结构域受体、异源三聚体G蛋白和肌醇三磷酸受体都已被证明在小窝中富集，这些发现表明细胞内肌醇三磷酸的产生和反应都高度分隔。
