Regulation Of EGFR And Its Family Members By RAB40C

ObjectiveFrom the perspective of the regulation of EGFR and its family members,we investigated the regulation of RAB40C on the expression of EGFR and its family members.In terms of mechanism,this study we clarified the detailed molecular mechanism of RAB40C regulation on the expression of EGFR and its family members.MethodsThe cells were cultured,and different plasmids and mutant plasmids were transfected into the cells,and was used to detect the protein expression by Western Blot.The regulation of EGFR and mutant expression and the regulation of cell specificity by RAB40C were analyzed in different cells;the specificity of RAB40C regulation of EGFR family members was analyzed.The molecular mechanism of RAB40C regulation of EGFR expression was analyzed from three aspects include general approach of protein degradation?EGFR and RAB40C.Immunohistochemistry the change of RAB40C in cancer cells.ResultsRAB40C significantly inhibits the expression of EGFR and also inhibits the oncogenic mutants of EGFR(EGFR^L858?EGFR^DEL?EGFRvIII).RAB40C also inhibits the expression of ERBB2 in the EGFR family,but does not inhibit other RTKs such as?MST1R?EGFR2?PDGFRB?.In terms of mechanism,proteasome inhibitors MG-132?PS-341 and lysosomal inhibitors chloroquine?HCQ?,Baf-A1 can not relieve the inhibitory effect of RAB40C on EGFR,but the proteolytic enzyme inhibitor Calpeptin can relieve the RAB40C inhibition of EGFR expression;RAB40C still has an inhibitory effect when EGFR kinase inhibitors Gefitinib is present or EGFR kinase inactivated mutants(EGFR^K721R?EGFR^K721M).The constitutive mutations in the GPTase domain of RAB40C(RAB40C^G28N?RAB40C^G28T?RAB40C^Q73L)has an inhibitory effect on EGFR expression,but its SOCS domain mutant(RAB40C^HL221-222AA?RAB40C^{LPL212-215AAAA})has no inhibitory effect on EGFR.ConclusionsRAB40C is a specific regulator of the EGFR family;this regulation is universal and it does not vary from cell to cell;it is also effective against oncogenic mutants of EGFR.The inhibition of EGFR expression by RAB40C is not through the proteasome or lysosomal pathways.Unlike the mechanisms already discovered,it may be a novel mechanism that is not currently discovered;RAB40C may regulate EGFR through a novel pathway independent of EGFR kinase activity.The regulation of EGFR by RAB40C is independent of the GTPase domain of RAB40C and it is dependent on the SOCS domain.