G-protein-coupled receptors and tyrosine kinases: crossroads in cell signaling and regulation.

G-protein-coupled receptors and protein tyrosine kinases represent two prominent pathways for cellular signaling. As our knowledge of cell signaling pathways mediated by the superfamily of G-protein-coupled receptors and the smaller family of receptor tyrosine kinases expands, so does our appreciation of how these two major signaling platforms share information and modulate each other, otherwise termed "cross-talk". Cross-talk between G-protein-coupled receptors and tyrosine kinases can occur at several levels, including the receptor-to-receptor level, and at crucial downstream points (e.g. phosphatidylinositol-3-kinase, Akt/protein kinase B and the mitogen-activated protein kinase cascade). Regulation of G-protein-coupled receptors by non-receptor tyrosine kinases, such as Src family members, also operates in signaling. A broader understanding of how G-protein-coupled receptors and tyrosine kinases cross-talk reveals new insights into signaling modalities in both health and disease.