Raaijmakers Judith H, Deneubourg Laurence, Rehmann Holger, de Koning John, Zhang Zhongchun, Krugmann Sonja, Erneux Christophe, Bos Johannes L
Department of Physiological Chemistry and Centre of Biomedical Genetics, UMC Utrecht, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands.
Cell Signal. 2007 Jun;19(6):1249-57. doi: 10.1016/j.cellsig.2006.12.015. Epub 2007 Jan 20.
Arap3 is a phosphoinositide (PI) 3 kinase effector that serves as a GTPase activating protein (GAP) for both Arf and Rho G-proteins. The protein has multiple pleckstrin homology (PH) domains that bind preferentially phosphatidyl-inositol-3,4,5-trisphosphate (PI(3,4,5,)P3) to induce translocation of Arap3 to the plasma membrane upon PI3K activation. Arap3 also contains a Ras association (RA) domain that interacts with the small G-protein Rap1 and a sterile alpha motif (SAM) domain of unknown function. In a yeast two-hybrid screen for new interaction partners of Arap3, we identified the PI 5'-phosphatase SHIP2 as an interaction partner of Arap3. The interaction between Arap3 and SHIP2 was observed with endogenous proteins and shown to be mediated by the SAM domain of Arap3 and SHIP2. In vitro, these two domains show specificity for a heterodimeric interaction. Since it was shown previously that Arap3 has a higher affinity for PI(3,4,5,)P3 than for PI(3,4)P2, we propose that the SAM domain of Arap3 can function to recruit a negative regulator of PI3K signaling into the effector complex.
Arap3是一种磷酸肌醇（PI）3激酶效应器，作为Arf和Rho G蛋白的GTP酶激活蛋白（GAP）发挥作用。该蛋白具有多个普列克底物蛋白同源（PH）结构域，这些结构域优先结合磷脂酰肌醇-3,4,5-三磷酸（PI(3,4,5)P3），从而在PI3K激活后诱导Arap3转位至质膜。Arap3还包含一个与小G蛋白Rap1相互作用的Ras关联（RA）结构域和一个功能未知的无活性α基序（SAM）结构域。在一项针对Arap3新相互作用伙伴的酵母双杂交筛选中，我们鉴定出PI 5'-磷酸酶SHIP2是Arap3的相互作用伙伴。Arap3与SHIP2之间的相互作用在内源蛋白中被观察到，并显示由Arap3和SHIP2的SAM结构域介导。在体外，这两个结构域对异二聚体相互作用具有特异性。由于先前已表明Arap3对PI(3,4,5)P3的亲和力高于对PI(3,4)P2的亲和力，我们提出Arap3的SAM结构域可发挥作用，将PI3K信号传导负调节因子招募到效应复合物中。
