Ci-VSP Is a Depolarization-activated Phosphatidylinositol-4,5-bisphosphate and Phosphatidylinositol-3,4,5-trisphosphate 5′-Phosphatase
Ci-VSP Is a Depolarization-activated Phosphatidylinositol-4,5-bisphosphate and Phosphatidylinositol-3,4,5-trisphosphate 5′-Phosphatase
复制标题
DOI：
10.1074/jbc.m803543200
复制
发表时间：
2009-01-23
影响因子：
4.8
通讯作者：
Oliver, Dominik
中科院分区：
文献类型：
--
作者：
Halaszovich, Christian R.;Schreiber, Daniela N.;Oliver, Dominik
磷酸肌醇是蛋白质功能的膜限调节剂，控制许多不同的细胞靶标。差异磷酸化同种型在各种亚细胞膜中具有不同的浓度，其可以响应细胞信号传导事件而动态变化。磷酸肌醇水平的维持和动态涉及一组复杂的酶，其中包括磷脂酶、脂质激酶和磷酸酶。最近，分离出一种含有电压传感器结构域的新型磷酸肌醇转换蛋白（称为 Ci-VSP）。已经表明 Ci-VSP 可以以电压依赖性方式改变磷酸肌醇水平。然而，Ci-VSP 催化的确切酶促反应尚不清楚。我们使用荧光磷酸肌醇结合探针和全内反射显微镜以及活细胞膜片钳测量来描绘 Ci-VSP 的底物和产物。通过膜去极化激活 Ci-VSP 后，磷脂酰肌醇 ( PI) (4,5)P-2- 和 PI(3,4,5)P-3 特异性结合域的膜缔合减少，表明 Ci-VSP 对这些磷酸肌醇的消耗。 PI(4,5)P-2 的消耗与膜 PI(4)P 的增加同时发生。类似地，PI(3,4)P-2 是在 PI(3,4,5)P-3 耗尽期间生成的。这些结果表明，Ci-VSP 充当 PI(4,5)P-2 和 PI(3,4,5)P-3 的 5'-磷酸酶。
Phosphoinositides are membrane-delimited regulators of protein function and control many different cellular targets. The differentially phosphorylated isoforms have distinct concentrations in various subcellular membranes, which can change dynamically in response to cellular signaling events. Maintenance and dynamics of phosphoinositide levels involve a complex set of enzymes, among them phospholipases and lipid kinases and phosphatases. Recently, a novel type of phosphoinositide-converting protein ( termed Ci-VSP) that contains a voltage sensor domain was isolated. It was already shown that Ci-VSP can alter phosphoinositide levels in a voltage-dependent manner. However, the exact enzymatic reaction catalyzed by Ci-VSP is not known. We used fluorescent phosphoinositide-binding probes and total internal reflection microscopy together with patch-clamp measurements from living cells to delineate substrates and products of Ci-VSP. Upon activation of Ci-VSP by membrane depolarization, membrane association of phosphatidylinositol ( PI) (4,5)P-2- and PI( 3,4,5)P-3-specific binding domains decreased, revealing consumption of these phosphoinositides by Ci-VSP. Depletion of PI(4,5)P-2 was coincident with an increase in membrane PI(4)P. Similarly, PI(3,4)P-2 was generated during depletion of PI(3,4,5)P-3. These results suggest that Ci-VSP acts as a 5'-phosphatase of PI(4,5)P-2 and PI(3,4,5)P-3.