CORK--A NOVEL, PUTATIVE ALPHA-2 INTEGRIN KINASE

α 2 β 1整联蛋白是一种胶原受体，参与血小板活化、平滑肌细胞和T淋巴细胞迁移、内皮附着和脉管系统中的其他事件。我们先前证明胶原诱导的血小板聚集依赖于这种整合素的占据（沿着一种未知的共受体，可能是糖蛋白VI）。我们还发现，胶原蛋白激活，在α 2 β 1依赖性的方式，非受体酪氨酸激酶Syk，其次是磷脂酶Cgamma 2，事件似乎是必要的胶原蛋白诱导的聚集。α 2 β 1整合素如何激活血小板或诱导这些信号转导事件尚不清楚。整合素领域的许多证据表明，整合素的短胞质结构域在将信号传递到细胞中中起关键作用，这可能是由于与这些结构域结合的调节分子。为了鉴定潜在的胞质结构域调节蛋白，我们在酵母双杂交系统中筛选文库，使用lapha 2整合素胞质结构域作为诱饵。我们已经确定了一个部分cDNA序列，它编码了一个非常有趣的蛋白质。该蛋白的mRNA很大（9.5kb），分布广泛，似乎在血小板、平滑肌细胞和其他血管和非血管细胞中表达。此外，核苷酸序列分析表明该蛋白质的一个区域与许多丝氨酸/苏氨酸和双特异性激酶高度同源，表明该蛋白质是激酶。一个单独的较小区域与RasGAP（一种Ras GTP酶激活蛋白）同源，并且实际上该蛋白在酵母双杂交系统中与Ras结合，但不与其他对照蛋白结合，这表明该蛋白也可能在调节Ras或Ras相关蛋白中起作用。我们建议首先完成编码该蛋白的cDNA的测序，其次进一步表征该蛋白的结构、细胞和组织分布以及功能。这种新蛋白的特性可能有助于我们更好地了解血小板和其他血管细胞中α 2 β 1介导的。

The alpha2gbeta1 integrin is a collagen receptor involved in platelet activation, smooth muscle cell and T lymphocyte migration, endothelial attachment and other events in the vasculature. We previously demonstrated that collagen-induced platelet aggregation depends upon occupancy of this integrin (along with an unknown co-receptor, possible glycoprotein VI). We also found that collagen activates, in an alpha2beta1-dependent manner, the non-receptor tyrosine kinase Syk, followed by phospholipase Cgamma2, events that appear necessary for collagen-induced aggregation. How the alpha2beta1 integrin activates platelets or induces these signal transduction events is unknown. Much evidence in the integrin field suggests that the short cytoplasmic domains of integrins play critical roles in transmitting signals into cells, potentially due to regulatory molecular that bind to these domains. To identify potential cytoplasmic domain regulatory proteins, we screened a library in the yeast two-hybrid system, using the lapha2 integrin cytoplasmic domain as bait. We have identified a partial cDNA sequence that encodes what appears to be an extremely interesting protein. The mRNA for this protein is large (9.5kb), widely distributed, and appears to be expressed in platelets, smooth muscle cells and other vascular and non-vascular cells. Moreover, nucleotide sequence analysis indicates a region of this protein that is highly homologous to numerous serine/threonine and dual specificity kinases, suggesting that the protein is a kinase. A separate smaller region is homologous to RasGAP, a Ras GTPase activating protein, and indeed this protein binds to Ras in the yeast two- hybrid system, but not to other control proteins, suggesting that his protein might also play a role in regulating Ras or Ras-related proteins. We propose to first complete the sequencing of the cDNA encoding this protein, and second to further characterize the protein with regard to its structure, cell and tissue distribution, and function. Characterizing of this novel protein may help us to better understand alpha2beta1-mediated in platelets and other vascular cells.