Interorganelle trafficking of ceramide is regulated by phosphorylation-dependent cooperativity between the PH and START domains of CERT
Interorganelle trafficking of ceramide is regulated by phosphorylation-dependent cooperativity between the PH and START domains of CERT
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DOI：
10.1074/jbc.m702291200
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发表时间：
2007-06-15
影响因子：
4.8
通讯作者：
Hanada, Kentaro
中科院分区：
文献类型：
--
作者：
Kumagai, Keigo;Kawano, Miyuki;Hanada, Kentaro
脂质的合成和转运是膜生物发生的重要事件。然而，很少有人知道细胞内的脂质运输是如何调节的。神经酰胺在内质网（ER）合成，并由神经酰胺转运蛋白CERT转运至高尔基体，在高尔基体中转化为鞘磷脂。CERT具有用于高尔基体靶向的磷酸肌醇结合普列克底物蛋白同源（PH）结构域和用于神经酰胺膜间转移的脂质转移START结构域。我们在这里表明，CERT接收多个丝氨酸重复基序，酪蛋白激酶I的一个可能的网站磷酸化，和磷酸化下调ER到高尔基体的神经酰胺运输。体外试验表明，磷酸化诱导PH和START结构域之间的自抑制相互作用，从而灭活磷酸肌醇结合和神经酰胺转移活性的CERT。鞘磷脂和胆固醇从细胞中的丢失引起CERT的去磷酸化而激活它，CERT功能不同结构域的协同控制是调节神经酰胺胞内运输的一种新的分子事件。
The synthesis and transport of lipids are essential events for membrane biogenesis. However, little is known about how intracellular trafficking of lipids is regulated. Ceramide is synthesized at the endoplasmic reticulum (ER) and transported by the ceramide transfer protein CERT to the Golgi apparatus, where it is converted to sphingomyelin. CERT has a phosphoinositidebinding pleckstrin homology (PH) domain for Golgi-targeting and a lipid transfer START domain for intermembrane transfer of ceramide. We here show that CERT receives multiple phosphorylations at a serine-repeat motif, a possibe site for casein kinase I, and that the phosphorylation down-regulates the ER-to-Golgi transport of ceramide. In vitro assays show that the phosphorylation induces an autoinhibitory interaction between the PH and START domains and consequently inactivates both the phosphoinositide binding and ceramide transfer activities of CERT. Loss of sphingomyelin and cholesterol from cells causes dephosphorylation of CERT to activate it. The cooperative control of functionally distinct domains of CERT is a novel molecular event to regulate the intracellular trafficking of ceramide.