Yi Yung-Hsiang, Ho Pei-Yun, Chen Tung-Wei, Lin Wen-Jie, Gukassyan Vladimir, Tsai Tsung-Heng, Wang Da-Wei, Lew Tien-Shen, Tang Chih-Yung, Lo Szecheng J, Chen Tsung-Yu, Kao Fu-Jen, Lin Chi-Hung
Institute of Microbiology and Immunology, National Yang-Ming University, Taipei 112, Taiwan.
J Biol Chem. 2009 Feb 6;284(6):3855-64. doi: 10.1074/jbc.M804334200. Epub 2008 Nov 7.
The cyclic calcium release and uptake during calcium oscillation are thought to result from calcium-induced calcium release (CICR); however, it is unclear, especially in nonexcitable cells, how the initial calcium mobilization that triggers CICR occurs. We report here a novel mechanism, other than conventional calcium channels or the phopholipase C-inositol trisphosphate system, for initiating calcium oscillation downstream of integrin signaling. Upon integrin alphaIIbbeta3 binding to fibrinogen ligand or the disintegrin rhodostomin, sodium-proton exchanger NHE1 and sodium-calcium exchanger NCX1 are actively transported to the plasma membrane, and they become physically coupled to integrin alphaIIbbeta3. Lipid raft-dependent mechanisms modulate the membrane targeting and formation of the NHE1-integrin alphaIIbbeta3-NCX1 protein complex. NHE1 and NCX1 within such protein complex are functionally coupled, such that a local increase of sodium concentration caused by NHE1 can drive NCX1 to generate sodium efflux in exchange for calcium influx. The resulting calcium increase inside the cell can then trigger CICR as a prelude to calcium oscillation downstream of integrin alphaIIbbeta3 signaling. Fluorescence resonance energy transfer based on fluorescence lifetime measurements is employed here to monitor the intermolecular interactions among NHE1-integrin alphaIIbbeta3-NCX1, which could not be properly detected using conventional biochemical assays.
钙振荡过程中钙的周期性释放和摄取被认为是由钙诱导的钙释放（CICR）所致；然而，目前尚不清楚，尤其是在非兴奋性细胞中，触发CICR的初始钙动员是如何发生的。我们在此报告一种新机制，不同于传统的钙通道或磷脂酶C-肌醇三磷酸系统，用于在整合素信号下游启动钙振荡。当整合素αIIbβ3与纤维蛋白原配体或去整合素罗多斯托明结合时，钠-质子交换体NHE1和钠-钙交换体NCX1被主动转运至质膜，并与整合素αIIbβ3发生物理偶联。脂筏依赖性机制调节NHE1-整合素αIIbβ3-NCX1蛋白复合物的膜靶向和形成。这种蛋白复合物中的NHE1和NCX1在功能上相互偶联，使得由NHE1引起的局部钠浓度升高能够驱动NCX1产生钠外流以交换钙内流。细胞内由此产生的钙增加随后可触发CICR，作为整合素αIIbβ3信号下游钙振荡的前奏。本文采用基于荧光寿命测量的荧光共振能量转移来监测NHE1-整合素αIIbβ3-NCX1之间的分子间相互作用，而使用传统生化检测方法无法对其进行适当检测。
