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Search for a Novel Gla-containing Growth Factor as the Ligand for Mer Receptor Tyrosine Kinase

寻找新型含 Gla 生长因子作为 Mer 受体酪氨酸激酶的配体

基本信息

批准号：
09680596
负责人：
MIZUNO Kensaku
金额：
$ 2.37万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09680596/
关键词：
Growth Factor Gas6 Receptor Tyrosine Kinase Mer Androgen-binding Protein Gla Domain

项目摘要

We previously identified that Gas6 is a common ligand for Axi, Sky, and Mer receptor tyrosine kinases. Quantitative binding analysis revealed that the binding affinity of Gas6 to Mer is relatively low, with a Kd value of 29.0 nM.Thus, we assumed the existence of the Gas6-related protein as a ligand for Mer receptor. In this study, we searched for the Gas6-related protein that may function as the preferable ligand for Mer. Gas6 has a structure similar to that of protein S and is composed of a Gla domain, four EGF-like domains and a C-terminal sex hormone-binding globulin (SHBG)- like domain. When examining the role of each domain in receptor-binding and biological activities of Gas6, we found that receptor-binding and mitogenic activities were markedly reduced by inhibiting gamma -carboxylation of the Gla domain, while a Gas6 mutant composed of only an SHBG-like domain retained both of these activities. Thus, the SHBG-like domain is apparently an entity indispensable for Gas6 activities, and gamma -carboxylation of the Gla domain has a regulatory role in retaining the activity of native Gas6. We searched for the cDNA clones coding for Gas6-related proteins, using PCR and low stringency hybridization techniques, but we failed to clone coding, for such protein. Androgen-binding protein, which has low sequence similarity to the SHBG-like domain of Gas6, showed no binding ability to Mer, Sky or Axl receptor. Thus, we have not detected any Gas6-related protein other than protein S.It could be that Gas6-induced activation of Mer require co-factors or co-receptors in living organisms. We also showed that Axl-Fc, a soluble form of AxI receptor composed of the extracellular domain of AxI and the Fc region of immunoglobulin, had an inhibitory function for the growth potentiating activity of Gas6 on vascular smooth muscle cells.

我们以前确定Gas 6是Axi，Sky和Mer受体酪氨酸激酶的常见配体。定量结合分析显示Gas 6与Mer的结合亲和力相对较低，Kd值为29.0 nM，因此，我们假设Gas 6相关蛋白作为Mer受体的配体存在。在这项研究中，我们寻找Gas 6相关的蛋白质，可能作为Mer的优选配体。Gas 6具有与蛋白S相似的结构，由一个Gla结构域、四个EGF样结构域和一个C末端性激素结合球蛋白（SHBG）样结构域组成。当检查每个结构域在Gas 6的受体结合和生物活性中的作用时，我们发现通过抑制Gla结构域的γ-羧化，受体结合和促有丝分裂活性显著降低，而仅由SHBG样结构域组成的Gas 6突变体保留了这两种活性。因此，SHBG样结构域显然是Gas 6活性不可或缺的实体，并且Gla结构域的γ-羧化在保持天然Gas 6的活性中具有调节作用。我们用PCR和低严格性杂交技术寻找编码Gas 6相关蛋白的cDNA克隆，但我们未能克隆编码这种蛋白的cDNA。雄激素结合蛋白与Gas 6的SHBG样结构域序列相似性较低，不与Mer、Sky或Axl受体结合。因此，我们没有检测到任何Gas 6相关的蛋白质以外的蛋白质S。这可能是Gas 6诱导的激活Mer需要辅因子或辅受体在活的生物体。我们还表明，Axl-Fc，一种可溶性形式的AxI受体的AxI的胞外结构域和免疫球蛋白的Fc区组成，具有抑制功能的Gas 6对血管平滑肌细胞的生长增强活性。