Lamorte Louie, Park Morag
Molecular Oncology Group, McGill University Hospital Centre, Department of Biochemistry, McGill University, Montreal, Quebec, Canada.
Anticancer Res. 2003 May-Jun;23(3A):2085-92.
Activation of the Met receptor tyrosine kinase through its ligand, hepatocyte growth factor (HGF), promotes an epithelial-mesenchymal transition and cell dispersal. However, little is known about the HGF-dependent signals that regulate these events. HGF stimulation of epithelial cell colonies leads to the enhanced recruitment of the CrkII and CrkL adapter proteins to Met-dependent signaling complexes. Overexpression of Crk adapter proteins in MDCK cells promotes spreading and loss of adherens junctions, events regulated by HGF. We recently demonstrated that the overexpression of CrkII promotes the formation of a multi-molecular complex containing CrkII, Paxillin and GIT-2, an ARF-GAP.
To determine the possible role of ARF1 and ARF6 in Crk- and HGF-dependent cell spreading, dominant negative mutants of ARF1 or ARF6 were microinjected into MDCK cells.
We report that MDCK cell lines overexpressing CrkII display reduced ARF6 but not ARF1 activity. While both ARF1 and ARF6 are required for the spreading of MDCK cells stimulated with HGF, ARF1 and ARF6 activity is dispensable for the spreading of cells microinjected with Crk.
We propose that Crk adapter proteins may act downstream of ARF1 and ARF6 to promote cell spreading or rely on different pathways to enhance cell spreading.
通过其配体肝细胞生长因子（HGF）激活Met受体酪氨酸激酶可促进上皮-间质转化和细胞扩散。然而，对于调节这些事件的HGF依赖性信号了解甚少。HGF刺激上皮细胞集落会导致CrkII和CrkL衔接蛋白更多地募集到Met依赖性信号复合物中。在MDCK细胞中过表达Crk衔接蛋白会促进细胞铺展和黏附连接的丧失，这些事件受HGF调节。我们最近证明，CrkII的过表达促进了包含CrkII、桩蛋白和GIT-2（一种ARF-GAP）的多分子复合物的形成。
为了确定ARF1和ARF6在Crk和HGF依赖性细胞铺展中的可能作用，将ARF1或ARF6的显性负性突变体显微注射到MDCK细胞中。
我们报告，过表达CrkII的MDCK细胞系显示ARF6活性降低，但ARF1活性未降低。虽然ARF1和ARF6都是HGF刺激的MDCK细胞铺展所必需的，但ARF1和ARF6活性对于显微注射Crk的细胞铺展是可有可无的。
我们提出，Crk衔接蛋白可能在ARF1和ARF6的下游发挥作用以促进细胞铺展，或者依赖不同途径增强细胞铺展。
