| Cell surface receptors that couple to heterotrimeric guanine nucleotide-binding (G) proteins mediate cellular responses to a large variety of external signals. How this signal transduction occurs is a matter involving complex and highly specific molecular relays. Among the known molecular signaling relays initiated with G protein-coupled receptors (GPCRs), those employing protein tyrosine kinases (PTKs) are possibly the least well understood.;I focused primarily on one of the best understood GPCRs, the m1 muscarinic acetylcholine receptor (mAChR), and a cytoplasmic PTK called PYK2, a member of the newly discovered focal adhesion kinase (FAK) family of PTKs. I found that stimulation of the m1 mAChR leads to the tyrosine phosphorylation and activation of PYK2. One readout of this GPCR-regulated PTK activity is the phosphorylation of the carboxy-terminal cytoplasmic tail of the Shaker family potassium channel Kv1.2, which has been implicated as a signaling target of PYK2.;Furthermore, using a stable cell line approach, I dissected components of the molecular events attending the regulation of PYK2 by m1 mAChRs. In addition to its own catalytic activity, phosphorylated PYK2 tyrosine residues Y402 and Y881 play key roles in regulating associations between the PTK and other cellular proteins, including c-Src, Grb2, and a ribosome-associating protein of unknown function called EWS. Taken together, these findings delineate a broad range of cellular events regulated by a single GPCR through a specific PTK. Beyond identifying a novel signal transduction pathway linking GPCRs to EWS, this research on the cooperation of GPCRs and PTKs contributes to a new groundwork for the study of cell-to-cell communication. |
