POSTRECEPTOR SIGNALING MECHANISMS FOR GROWTH-HORMONE

Recent data have shed significant new light on the mechanisms involved in the transmission of a biologic signal by GH. Following ligand-indu ced dimerization of the GH receptor multiple cascades are involved in GH signaling. These include activation of nonreceptor tyrosine kinases , in particular JAK2, which is a mechanism shared by the newly describ ed cytokine receptor superfamily. Furthermore, several classic pathway s (for example, guanine-nucleotide-binding proteins and protein kinase C), shared by numerous hormones, growth factors, and neurotransmitter s, are also involved in many of the actions of GH. The interrelationsh ips between the various signaling pathways for GH have not yet been fu lly defined. This review briefly summarizes the current state of knowl edge with respect to the processes involved in the effects of GH in ta rget cells.