Role Of Intersectin Adaptor Protein In Regulation Of End

工作总结：我们小组感兴趣的是了解交叉素(ITSN)接头蛋白在调节信号转导通路中的作用，特别是受体酪氨酸激酶(RTK)。ITSN是一个不断增长的适配器蛋白家族的成员，它拥有保守的Eps15同源(EH)结构域以及额外的蛋白质识别基序。含EH的蛋白质在调节依赖于笼蛋白的内吞作用中起着不可或缺的作用。ITSN由两个NH4末端的EH结构域、一个卷曲线圈(CC)区域和5个串联的Src同源3(SH3)结构域组成。此外，ITSN还有一个更大的剪接变体，称为ITSN-L，它具有编码DBL同源(DH)结构域、Pleckstrin同源(PH)结构域和C2结构域的COOH-末端延伸。DH结构域是Ras类GTP酶的Rho亚家族的鸟嘌呤核苷酸交换因子(GEF)，包括Rho、Rac和Cdc42。这些结构域与直接与脂质和膜相互作用的PH结构域协同工作。因此，ITSN-L可能在神经系统内调节Rho家族的激活。C2结构域结合磷脂膜、蛋白质或可溶性肌醇多磷酸，既依赖于钙离子，也不依赖于钙离子。虽然各种实验都表明ITSN参与了内吞作用的调节，但我们现在已经证明了ITSN激活了信号转导通路。过去十年的研究表明，内吞作用和有丝分裂信号之间存在联系。因此，我们的发现表明，ITSN可能是这两个细胞过程之间的一个可能的分子联系。我们目前的重点是了解ITSN激活信号通路的机制。ITSN的靶标之一是ELK-1转录因子。虽然ELK-1经典地被认为是RAS-MAPK通路的靶标，但我们已经证明ITSN以MEK和MAPK非依赖性的方式激活ELK-1。因此，ITSN似乎刺激了一条与经典的RAS-MAPK途径不同的途径，以激活ELK-1。我们正在确定这条途径的性质。此外，我们还想确定这一信号活动对ITSN功能的重要性。鉴于ITSN在内吞作用中的调节作用，我们目前正在研究ITSN通过调节RTK内吞、循环和降解来调节RTK功能的可能功能。

Summary of Work: Our group is interested in understanding the role of the Intersectin (ITSN) adaptor protein in regulating signal transduction cascades in general and receptor tyrosine kinases (RTKs) in particular. ITSN is a member of a growing family of adaptor proteins that possess conserved Eps15 homology (EH) domains as well as additional protein recognition motifs. EH-containing proteins play an integral role in regulating clathrin-dependent endocytosis. ITSN consists of two NH4-terminal EH domains, a coiled-coil (CC) region and 5 tandem Src homology 3 (SH3) domains. In addition, there is a larger splice variant of ITSN, termed ITSN-L, which possess a COOH-terminal extension encoding a Dbl homology (DH) domain, a Pleckstrin homology (PH) domain and a C2 domain . DH domains function as guanine nucleotide exchange factors (GEFs) for the Rho subfamily of Ras-like GTPases which include Rho, Rac and Cdc42. These domains function in concert with PH domains which direct interaction with lipids and membrane. Thus, ITSN-L may serve to regulate Rho family activation within the nervous system. C2 domains bind phospholipid membranes, proteins or soluble inositol polyphosphates using both Ca+2-dependent and -independent mechanisms. Although a variety of experiments have implicated ITSN in the regulation of endocytosis, we have now demonstrated that ITSN activates signal transduction pathways. Research over the past decade has suggested a link between endocytosis and mitogenic signaling. Thus, our findings suggest that ITSN may be one possible molecular link between these two cellular processes. Our current focus is on understanding the mechanism by which ITSN activates signaling pathways. One of the targets of ITSN is the Elk-1 transcription factor. Although Elk-1 is classically known as a target of the Ras-MAPK pathway, we have demonstrated that ITSN activates Elk-1 in a MEK and MAPK-independent manner. Thus, ITSN appears to stimulate a pathway distinct from the classic Ras-MAPK pathway in order to activate Elk-1. We are in the process of determining the nature of this pathway. In addition we want to determine the importance of this signaling activity for ITSN function. Given the role of ITSN in the regulation of endocytosis, we are currently examining the possible function of ITSN in modulating RTK function through regulation of RTK endocytosis, recycling and degradation.