The Mechanism Of Rap2Signaling Pathway Regulating Renal Cell Carcinoma Migration And Invasion

Rap2, a Ras family small G protein, includes Rap2A, Rap2B and Rap2C threeisoforms, regulating multiple cellular activities. As Rap2showed structuralsimilarity with other Ras family small G proteins, it shares several proteins withother member of Ras family. In addition, Rap2is involved in binding specificpatterns signaling pathway other than Ras members through its specific bindingproteins. So far, four kinds of Rap2-specific-reaction-proteins including PARG,TNIK, MINK and MAP4K4have been identified. However, their functions duringtumor formation still remain to be investigated.In the previous study, the data shows that the activity of Rap2is higher in renalcell carcinoma than the adjacent normal tissue, and the ectopic expression of Rap2in renal cells promoted cell migration. However, it still remains unknown that themechanism for the higher activity of Rap2in renal cancer tissues, and how thehigher activity contributes to cell migration and invasion. In this study, weinvestigated the activity of Rap2in renal cancer cell lines by GST pull down assay,and analyzed the expression level of Rap1GAP1and RasGEF1B in different renalcancer cell lines. The results showed that the activity of Rap2was increased largelyin renal cancer cells, and suggested that the increased activity of Rap2in renalcancer cell may due to the regulation of expression of Rap1GAP1and RasGEF1B,the negative regulator and positive regulator for Rap2signaling. To understand thesignaling pathway for Rap2to regulate cell migration and invasion, TNIK andMAP4K4, the Rap2downstream effectors, were silenced by RNAi method, and cellmigration ability were analyzed by wound healing and transwell assay. The resultsindicated that Rap2promoted renal cell migration and invasion through TNIK andMAP4K4. It is reported that FAK could positively regulated cell migration andcancer cell invasion. In this study, we confirmed that Rap2or Rap2-12V, the activemutant of Rap2,rather than Rap2-17N was able to increase that expression level ofFAK. In summery, our results improved the understanding of mechanism of higheractivity of Rap2in renal cancer cells Rap2-dependent and signaling pathwaystoward cell migration and cell invasion.