Vihanto Meri M, Vindis Cecile, Djonov Valentin, Cerretti Douglas P, Huynh-Do Uyen
Department of Nephrology and Hypertension, Inselspital, University of Bern, Switzerland.
J Cell Sci. 2006 Jun 1;119(Pt 11):2299-309. doi: 10.1242/jcs.02946.
Eph receptor tyrosine kinases are key players during the development of the embryonic vasculature; however, their role and regulation in adult angiogenesis remain to be defined. Caveolae are flask-shaped invaginations of the cell membrane; their major structural protein, caveolin-1, has been shown to regulate signaling molecules localized in these micro-domains. The interaction of caveolin-1 with several of these proteins is mediated by the binding of its scaffolding domain to a region containing hydrophobic amino acids within these proteins. The presence of such a motif within the EphB1 kinase domain prompted us to investigate the caveolar localization and regulation of EphB1 by caveolin-1. We report that EphB1 receptors are localized in caveolae, and directly interact with caveolin-1 upon ligand stimulation. This interaction, as well as EphB1-mediated activation of extracellular-signal-regulated kinase (ERK), was abrogated by overexpression of a caveolin-1 mutant lacking a functional scaffolding domain. Interaction between Ephs and caveolin-1 is not restricted to the B-subclass of receptors, since we show that EphA2 also interacts with caveolin-1. Furthermore, we demonstrate that the caveolin-binding motif within the kinase domain of EphB1 is primordial for its correct membrane targeting. Taken together, our findings establish caveolin-1 as an important regulator of downstream signaling and membrane targeting of EphB1.
Eph受体酪氨酸激酶是胚胎血管系统发育过程中的关键因子；然而，它们在成人血管生成中的作用和调控仍有待确定。小窝是细胞膜呈烧瓶状的内陷结构；其主要结构蛋白小窝蛋白-1已被证明可调节定位于这些微区的信号分子。小窝蛋白-1与其中几种蛋白的相互作用是由其支架结构域与这些蛋白中包含疏水氨基酸的区域结合介导的。EphB1激酶结构域中存在这样一个基序促使我们研究小窝蛋白-1对EphB1的小窝定位和调控。我们报告EphB1受体定位于小窝，并在配体刺激后直接与小窝蛋白-1相互作用。这种相互作用以及EphB1介导的细胞外信号调节激酶（ERK）的激活被缺乏功能性支架结构域的小窝蛋白-1突变体的过表达所消除。Ephs与小窝蛋白-1之间的相互作用并不局限于受体的B亚类，因为我们发现EphA2也与小窝蛋白-1相互作用。此外，我们证明EphB1激酶结构域内的小窝结合基序对其正确的膜靶向至关重要。综上所述，我们的研究结果表明小窝蛋白-1是EphB1下游信号传导和膜靶向的重要调节因子。
