Mohney Robert P, Das Margaret, Bivona Trever G, Hanes Richard, Adams Anthony G, Philips Mark R, O'Bryan John P
Laboratory of Signal Transduction, National Institute of Environmental Health Services, NIH/DHHS, Building 101, Research Triangle Park, NC 27709, USA.
J Biol Chem. 2003 Nov 21;278(47):47038-45. doi: 10.1074/jbc.M303895200. Epub 2003 Sep 11.
Intersectin (ITSN) is a molecular scaffold involved in regulating endocytosis and mitogenic signaling. We previously demonstrated that ITSN transformed rodent fibroblasts, accelerated hormone-induced maturation of Xenopus oocytes, and activated the Elk-1 transcription factor through an MEK- and Erk-independent mechanism. We now demonstrate that ITSN complexes with the Ras guanine nucleotide exchange factor Sos1 leading to increased RasGTP levels. Using fluorescence resonant energy transfer analysis, we demonstrate that ITSN complexes with Ras in living cells leading to Ras activation on intracellular vesicles. These vesicles contain epidermal growth factor receptor but are distinct from transferrin-positive vesicles. However, Ras is not required for ITSN stimulation of transcription. Rather, we demonstrate that ITSN signals through JNK to activate Elk-1. Although ITSN activation of Elk-1 was Ras-independent, ITSN cooperates with Ras to synergistically activate JNK. These findings indicate that ITSN activates multiple intracellular signaling pathways and suggest that this adaptor protein may coordinately regulate the activity of these pathways in vivo.
相交蛋白（ITSN）是一种参与调节内吞作用和有丝分裂信号传导的分子支架。我们之前证明，ITSN可转化啮齿动物成纤维细胞，加速激素诱导的非洲爪蟾卵母细胞成熟，并通过一种不依赖MEK和Erk的机制激活Elk-1转录因子。我们现在证明，ITSN与Ras鸟嘌呤核苷酸交换因子Sos1形成复合物，导致RasGTP水平升高。通过荧光共振能量转移分析，我们证明ITSN在活细胞中与Ras形成复合物，导致细胞内囊泡上的Ras激活。这些囊泡含有表皮生长因子受体，但与转铁蛋白阳性囊泡不同。然而，Ras并非ITSN刺激转录所必需。相反，我们证明ITSN通过JNK发出信号以激活Elk-1。尽管ITSN对Elk-1的激活不依赖Ras，但ITSN与Ras协同激活JNK。这些发现表明，ITSN激活多种细胞内信号通路，并提示这种衔接蛋白可能在体内协调调节这些通路的活性。
