Activity-dependent interaction of the intracellular domain of rat TrkA with intermediate filament proteins, the beta-6 proteasomal subunit, Ras-GRF1,and the p162 subunit of eIF3

Many responses to nerve growth factor (NGF) are regulated through the recep tor tyrosine kinase trkA. To understand more fully the functions of trkA in NGF responsive cells, we have expressed the intracellular domain of rat tr kA as a fusion protein with the yeast gal4 transcription factor, and used t he fusion pro rein to probe Pat and mouse cDNA libraries by the yeast two-h ybrid system. We have identified a direct interaction between the intracell ular domain of trkA and two members of the intermediate filament (IF) famil y of proteins, the guanine-nucleotide exchange protein Ras-GRF1, the p162 s ubunit of eIF3, and the beta-6 proteasome subunit. The interactions are dep endent on an active trkA kinase, and RasGRF1, the beta-6 proteasomal subuni t, and peripherin are directly phosphorylated by trkA. The interaction with trkA is not affected by mutations at either Tyr(499) or Tyr(794), the two major phosphotyrosine residues essential to the activation and receptor bin ding of Shc, FRS-2/SNT, and phospholipase C gamma-1, and it is highly speci fic in vitro for trkA, with little or no binding observed with trkB and/or trkC. The results show that trkA may play a regulatory Pole in a variety of cellular functions in addition to neuritogenesis, including regulated prot ein degradation and transcriptional activation.