G-protein regulatory pathways: rocketing into the twenty-first century.

Complex cellular responses involve the integration of heterotrimeric G protein systems with protein kinase signal transduction pathways. Key in this integration is the control of small GTP-binding proteins including Ras and Rho family members. In this paper, we discuss the control of signal transduction pathways by G proteins and their integration with specific tyrosine kinases. The integration of G proteins, kinases, and small GTP-binding proteins in controlling cellular responses is illustrated through the newly defined G alpha 12/13-regulated pathways. Furthermore, the polymorphonuclear leukocyte provides a primary cell system for analyzing the integration of G proteins, kinases, and small GTP-binding proteins in controlling cellular functions such as superoxide production, adherence, chemotaxis, and granule secretion.