Membrane Targeting and Coupling of NHE1-IntegrinαIIbβ3-NCX1 by Lipid Rafts following Integrin-Ligand Interactions Trigger Ca2+ Oscillations

• Published in: The Journal of biological chemistry Vol. 284; no. 6; p. 3855
• Main Authors: Yung-Hsiang Yi, Pei-Yun Ho, Tung-Wei Chen, Wen-Jie Lin, Vladimir Gukassyan, Tsung-Heng Tsai, Da-Wei Wang, Tien-Shen Lew, Chih-Yung Tang, Szecheng J. Lo, Tsung-Yu Chen, Fu-Jen Kao, Chi-Hung Lin
• Format: Journal Article
• Language: English
• Published: American Society for Biochemistry and Molecular Biology 06.02.2009
• DOI: 10.1074/jbc.M804334200
• ISSN: 0021-9258

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 α IIb β 3 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 α IIb β 3 . Lipid raft-dependent mechanisms modulate the membrane targeting and formation of the NHE1-integrin α IIb β 3 -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 α IIb β 3 signaling. Fluorescence resonance energy transfer based on fluorescence lifetime measurements is employed here to monitor the intermolecular interactions among NHE1-integrin α IIb β 3 -NCX1, which could not be properly detected using conventional biochemical assays.