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

Many responses to nerve growth factor (NGF) are regulated through the receptor tyrosine kinase trkA. To understand more fully the functions of trkA in NGF responsive cells, we have expressed the intracellular domain of rat trkA as a fusion protein with the yeast gal4 transcription factor, and used the fusion pro rein to probe Pat and mouse cDNA libraries by the yeast two-hybrid system. We have identified a direct interaction between the intracellular domain of trkA and two members of the intermediate filament (IF) family of proteins, the guanine-nucleotide exchange protein Ras-GRF1, the p162 subunit of eIF3, and the beta-6 proteasome subunit. The interactions are dependent on an active trkA kinase, and RasGRF1, the beta-6 proteasomal subunit, 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 binding of Shc, FRS-2/SNT, and phospholipase C gamma-1, and it is highly specific 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 protein degradation and transcriptional activation.