ACTIVATION OF PROTEIN-TYROSINE KINASE PYK2 BY THE M1 MUSCARINIC ACETYLCHOLINE-RECEPTOR

Several G protein-coupled receptors are known to direct the tyrosine p hosphorylation, and in some cases the activation, of diverse tyrosine kinases, Using a stable cell line approach, we characterize the activa tion of PYK2, a tyrosine kinase structurally related to focal adhesion kinase, by the G protein-coupled m1 muscarinic acetylcholine receptor . We find that PYK2 tyrosine kinase activity is critical for the m1 re ceptor-stimulated tyrosine phosphorylation of PYK2. Furthermore, we id entify two tyrosine residues that are subject to phosphorylation in re sponse to muscarinic signaling and show that this phosphorylation indu ces two cytosolic proteins, c-Src and Grb2, to bind to PYK2, This is t he first demonstration of the significance played by distinct PYK2 tyr osine residues in G protein-coupled signaling to this kinase, By compa rison, though m1 receptors induce the tyrosine phosphorylation of the cytoskeletal protein paxillin, the association of paxillin with PYK2 i s unaffected by muscarinic signaling. We also provide evidence that PY K2 specifically phosphorylates the carboxyl-terminal cytosolic portion of the potassium channel Kv1.2 in a manner regulated by the m1 recept or. These results delineate molecular events attending the m1 muscarin ic receptor stimulation of this tyrosine kinase and establish PYK2 as an effector of the m1 muscarinic receptor in the regulation of multipl e cell functions.