Cambridge Institute for Medical Research, University of Cambridge Wellcome Trust/Medical Research Council Building, Hills Road, Cambridge CB2 0XY, United Kingdom.
Proc Natl Acad Sci U S A. 2010 Oct 12;107(41):17539-44. doi: 10.1073/pnas.1007974107. Epub 2010 Sep 27.
Regulation of membrane lipid composition is crucial for many aspects of cell growth and development. Lipins, a novel family of phosphatidate (PA) phosphatases that generate diacylglycerol (DAG) from PA, are emerging as essential regulators of fat metabolism, adipogenesis, and organelle biogenesis. The mechanisms that govern lipin translocation onto membranes are largely unknown. Here we show that recruitment of the yeast lipin (Pah1p) is regulated by PA levels onto the nuclear/endoplasmic reticulum (ER) membrane. Recruitment requires the transmembrane protein phosphatase complex Nem1p-Spo7p. Once dephosphorylated, Pah1p can bind to the nuclear/ER membrane independently of Nem1p-Spo7p via a short amino-terminal amphipathic helix. Dephosphorylation enhances the activity of Pah1p, both in vitro and in vivo, but only in the presence of a functional helix. The helix is required for both phospholipid and triacylglycerol biosynthesis. Our data suggest that dephosphorylation of Pah1p by the Nem1p-Spo7p complex enables the amphipathic helix to anchor Pah1p onto the nuclear/ER membrane allowing the production of DAG for lipid biosynthesis.
膜脂组成的调节对于细胞生长和发育的许多方面都至关重要。脂磷酰肌醇（lipin）是一种新型的磷酸二酰甘油（PA）磷酸酶家族，可将 PA 转化为二酰基甘油（DAG），它作为脂肪代谢、脂肪生成和细胞器生物发生的重要调节剂而出现。控制脂磷酰肌醇向膜上移位的机制在很大程度上尚不清楚。在这里，我们表明酵母脂磷酰肌醇（Pah1p）的募集受核/内质网（ER）膜上 PA 水平的调节。募集需要跨膜蛋白磷酸酶复合物 Nem1p-Spo7p。一旦去磷酸化，Pah1p 可以通过短的氨基末端两亲性螺旋独立于 Nem1p-Spo7p 结合到核/ER 膜上。去磷酸化可增强 Pah1p 的体外和体内活性，但仅在存在功能螺旋的情况下才如此。该螺旋对于磷脂和三酰基甘油的生物合成都是必需的。我们的数据表明，Nem1p-Spo7p 复合物对 Pah1p 的去磷酸化使两亲性螺旋能够将 Pah1p 锚定到核/ER 膜上，从而为脂质生物合成产生 DAG。
