Protein Phosphatase 1α Mediates Ceramide-induced ERM Protein Dephosphorylation A NOVEL MECHANISM INDEPENDENT OF PHOSPHATIDYLINOSITOL 4, 5-BIPHOSPHATE (PIP2) AND MYOSIN/ERM PHOSPHATASE
Protein Phosphatase 1α Mediates Ceramide-induced ERM Protein Dephosphorylation A NOVEL MECHANISM INDEPENDENT OF PHOSPHATIDYLINOSITOL 4, 5-BIPHOSPHATE (PIP2) AND MYOSIN/ERM PHOSPHATASE
复制标题
DOI：
10.1074/jbc.m111.306456
复制
发表时间：
2012-03-23
影响因子：
4.8
通讯作者：
Hannun, Yusuf A.
中科院分区：
文献类型：
--
作者：
Canals, Daniel;Roddy, Patrick;Hannun, Yusuf A.
ERM（ezrin、radixin和moesin）蛋白是与皮质肌动蛋白、质膜和膜蛋白结合的细胞骨架相互作用蛋白，其在专门的质膜结构如微绒毛和丝状伪足中发现。ERM蛋白受磷脂酰肌醇4，5-二磷酸（PIP 2）和C-末端苏氨酸的磷酸化调节，并且其失活涉及PIP 2水解和/或肌球蛋白磷酸酶（MP）。最近，我们证明，ERM蛋白也受到反调节的生物活性鞘脂神经酰胺和鞘氨醇1-磷酸。质膜神经酰胺诱导ERM去磷酸化，而1-磷酸鞘氨醇诱导其磷酸化。在这项工作中，我们追求神经酰胺调节去磷酸化的机制。我们发现，这种去磷酸化是独立的水解和定位的PIP 2和MP。然而，结果显示，通过用蛋白磷酸酶1（PP 1）药理学抑制剂和特异性地通过针对PP 1 α的siRNA处理来阻断ERM去磷酸化，而冈田酸（PP 2A抑制剂）失败。此外，PP 1 α的催化失活突变体作为内源性PP 1 α的显性负性。其他结果表明，PP 1 α激活的神经酰胺机制在很大程度上不依赖于PIP 2水解和MP。综上所述，这些结果证明了一种新的，急性的ERM调节机制依赖于PP 1 α和质膜神经酰胺。
ERM (ezrin, radixin, and moesin) proteins are cytoskeletal interacting proteins that bind cortical actin, the plasma membrane, and membrane proteins, which are found in specialized plasma membrane structures such as microvilli and filopodia. ERM proteins are regulated by phosphatidylinositol 4, 5-biphosphate (PIP2) and by phosphorylation of a C-terminal threonine, and its inactivation involves PIP2 hydrolysis and/or myosin phosphatase (MP). Recently, we demonstrated that ERM proteins are also subject to counter regulation by the bioactive sphingolipids ceramide and sphingosine 1-phosphate. Plasma membrane ceramide induces ERM dephosphorylation whereas sphingosine 1-phosphate induces their phosphorylation. In this work, we pursue the mechanisms by which ceramide regulates dephosphorylation. We found that this dephosphorylation was independent of hydrolysis and localization of PIP2 and MP. However, the results show that ERM dephosphorylation was blocked by treatment with protein phosphatase 1 (PP1) pharmacological inhibitors and specifically by siRNA to PP1 alpha, whereas okadaic acid, a PP2A inhibitor, failed. Moreover, a catalytic inactive mutant of PP1 alpha acted as dominant negative of the endogenous PP1 alpha. Additional results showed that the ceramide mechanism of PP1 alpha activation is largely independent of PIP2 hydrolysis and MP. Taken together, these results demonstrate a novel, acute mechanism of ERM regulation dependent on PP1 alpha and plasma membrane ceramide.