Tcherkezian Joseph, Triki Ibtissem, Stenne Raphaelle, Danek Eric I, Lamarche-Vane Nathalie
Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, Canada H3A 2B2.
Biol Cell. 2006 Aug;98(8):445-56. doi: 10.1042/BC20050101.
Rho GTPases regulate a wide range of cellular functions affecting both cell proliferation and cytoskeletal dynamics. They cycle between inactive GDP- and active GTP-bound states. This cycle is tightly regulated by GEFs (guanine nucleotide-exchange factors) and GAPs (GTPase-activating proteins). Mouse CdGAP (mCdc42 GTPase-activating protein) has been previously identified and characterized as a specific GAP for Rac1 and Cdc42, but not for RhoA. It consists of an N-terminal RhoGAP domain and a C-terminal proline-rich region. In addition, CdGAP-related genes are present in both vertebrates and invertebrates. We have recently reported that two predominant isoforms of CdGAP (250 and 90 kDa) exist in specific mouse tissues.
In the present study, we have identified and characterized human CdGAP (KIAA1204) which shares 76% sequence identity to the long isoform of mCdGAP (mCdGAP-l). Similar to mCdGAP, it is active in vitro and in vivo on both Cdc42 and Rac1, but not RhoA, and is phosphorylated in vivo on serine and threonine residues. In contrast with mCdGAP-l, human CdGAP interacts with ERK1/2 (extracellular-signal-regulated kinase 1/2) through a region that does not involve a DEF (docking site for ERK Phe-Xaa-Phe-Pro) domain. Also, the tissue distribution of CdGAP proteins appears to be different between human and mouse species. Interestingly, we found that CdGAP proteins cause membrane blebbing in COS-7 cells.
Our results suggest that CdGAP properties are well conserved between human and mouse species, and that CdGAP may play an unexpected role in apoptosis.
Rho GTP酶调节广泛的细胞功能，影响细胞增殖和细胞骨架动力学。它们在无活性的GDP结合状态和活性的GTP结合状态之间循环。这个循环受到鸟嘌呤核苷酸交换因子（GEFs）和GTP酶激活蛋白（GAPs）的严格调控。小鼠CdGAP（mCdc42 GTP酶激活蛋白）先前已被鉴定并表征为Rac1和Cdc42的特异性GAP，但不是RhoA的GAP。它由一个N端RhoGAP结构域和一个C端富含脯氨酸的区域组成。此外，CdGAP相关基因在脊椎动物和无脊椎动物中均有存在。我们最近报道，CdGAP的两种主要异构体（250和90 kDa）存在于特定的小鼠组织中。
在本研究中，我们鉴定并表征了人类CdGAP（KIAA1204），它与mCdGAP的长异构体（mCdGAP-l）具有76%的序列同一性。与mCdGAP相似，它在体外和体内对Cdc42和Rac1均有活性，但对RhoA无活性，并且在体内丝氨酸和苏氨酸残基上被磷酸化。与mCdGAP-l不同，人类CdGAP通过一个不涉及DEF（ERK苯丙氨酸-任一氨基酸-苯丙氨酸-脯氨酸对接位点）结构域的区域与ERK1/2（细胞外信号调节激酶1/2）相互作用。此外，CdGAP蛋白的组织分布在人类和小鼠物种之间似乎有所不同。有趣的是，我们发现CdGAP蛋白在COS-7细胞中引起膜泡形成。
我们的结果表明，CdGAP的特性在人类和小鼠物种之间得到了很好的保留，并且CdGAP可能在细胞凋亡中发挥意想不到的作用。
