Changes in membrane curvature are required to control the function of subcellular compartments; malfunctions of such processes are associated with a wide range of human diseases. Membrane remodeling often depends upon the presence of phosphoinositides, which recruit protein effectors for a variety of cellular functions. Phafin2 is a phosphatidylinositol 3-phosphate (PtdIns3P)-binding effector involved in endosomal and lysosomal membrane-associated signaling. Both the Phafin2 PH and the FYVE domains bind PtdIns3P, although their redundant function in the protein is unclear. Through a combination of lipid-binding assays, we found that, unlike the FYVE domain, recognition of the PH domain to PtdIns3P requires a lipid bilayer. Using site-directed mutagenesis and truncation constructs, we discovered that the Phafin2 FYVE domain is constitutive for PtdIns3P binding, whereas PH domain binding to PtdIns3P is autoinhibited by a conserved C-terminal acidic motif. These findings suggest that binding of the Phafin2 PH domain to PtdIns3P in membrane compartments occurs through a highly regulated mechanism. Potential mechanisms are discussed throughout this report.

中文翻译：

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Phafin2的C端酸性基序抑制PH结构域结合磷脂酰肌醇3-磷酸。

需要改变膜曲率来控制亚细胞区室的功能。这些过程的故障与多种人类疾病有关。膜重塑通常取决于磷酸肌醇的存在，该磷酸肌醇募集蛋白质效应子以用于多种细胞功能。Phafin2是磷脂酰肌醇3-磷酸（PtdIns3P）结合效应子，参与内体和溶酶体膜相关信号传导。Phafin2 PH和FYVE结构域都结合PtdIns3P，尽管它们在蛋白质中的冗余功能尚不清楚。通过结合脂质结合测定，我们发现与FYVE域不同，PtdIns3P对PH域的识别需要脂质双层。使用定点诱变和截短构建体，我们发现，Phafin2 FYVE域对于PtdIns3P结合是组成性的，而与PtdIns3P结合的PH域则被保守的C端酸性基序自动抑制。这些发现表明，Phafin2 PH结构域与膜区室中的PtdIns3P的结合是通过高度调控的机制发生的。在本报告全文中讨论了潜在的机制。