Identification and Molecular Mechanisms of the Rapid Tonicity-induced Relocalization of the Aquaporin 4 Channel.
Identification and Molecular Mechanisms of the Rapid Tonicity-induced Relocalization of the Aquaporin 4 Channel.
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DOI：
10.1074/jbc.m115.646034
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发表时间：
2015-07-03
期刊：
影响因子：
--
通讯作者：
Conner AC
中科院分区：
文献类型：
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作者：
Kitchen P;Day RE;Taylor LH;Salman MM;Bill RM;Conner MT;Conner AC
背景：水通道蛋白水通道蛋白 4 (AQP4) 控制血脑屏障的水渗透性。结果：低渗性以钙、钙调蛋白和激酶依赖性方式诱导 AQP4 快速重新定位。结论：AQP4可以在细胞膜和细胞内区室之间重新定位。意义：AQP4膜定位的药理学调节可以提供治疗脑水肿的新方法。完整膜蛋白的水通道蛋白家族由介导细胞水流的通道组成。水通道蛋白 4 (AQP4) 在中枢神经系统的神经胶质细胞中高度表达，并促进与中风和创伤性脑损伤相关的渗透驱动的病理性脑肿胀。在这里，我们表明，在原代皮质大鼠星形胶质细胞和转染的 HEK293 细胞中，AQP4 细胞表面表达可以响应张力的变化而快速、可逆地调节。易位机制涉及PKA激活、细胞外钙流入和钙调蛋白激活。我们确定了五个假定的 PKA 磷酸化位点，并使用定点诱变来表明，只有这些位点之一（丝氨酸 276）的磷酸化对于易位反应是必需的。我们在确定治疗脑水肿的新治疗方法的背景下讨论我们的发现。
Background: The water channel protein aquaporin 4 (AQP4) controls water permeability of the blood-brain barrier. Results: Hypotonicity induces rapid relocalization of AQP4 in a calcium-, calmodulin-, and kinase-dependent manner. Conclusion: AQP4 can be relocalized between the cell membrane and intracellular compartments. Significance: Pharmacological modulation of AQP4 membrane localization could provide a new approach to treating brain edema. The aquaporin family of integral membrane proteins is composed of channels that mediate cellular water flow. Aquaporin 4 (AQP4) is highly expressed in the glial cells of the central nervous system and facilitates the osmotically driven pathological brain swelling associated with stroke and traumatic brain injury. Here we show that AQP4 cell surface expression can be rapidly and reversibly regulated in response to changes of tonicity in primary cortical rat astrocytes and in transfected HEK293 cells. The translocation mechanism involves PKA activation, influx of extracellular calcium, and activation of calmodulin. We identify five putative PKA phosphorylation sites and use site-directed mutagenesis to show that only phosphorylation at one of these sites, serine 276, is necessary for the translocation response. We discuss our findings in the context of the identification of new therapeutic approaches to treating brain edema.