Growth factor receptor-bound protein 2 (Grb2) association with hemopoietic specific protein 1: linkage between Lck...

To analyze the growth factor receptor-bound protein 2 (Grb2) signaling pathway in lymphoid cells, we used expression cloning to isolate the genes encoding proteins that associate with Grb2. We find that the Src homology 3 domains of Grb2 directly associate, in vitro and in vivo, with murine hemopoietic specific protein 1 (HS1), a protein identical to Lck-binding protein 1. Because HS1 associates with the p56(lck) and p59(lyn) tyrosine kinases in vitro and in vivo, and becomes tyrosine phosphorylated upon various receptor stimulations, our present data suggest that HS1 mediates linkage between Lck or Lyn and Grb2 in lymphoid lineage cells.