INTRACELLULAR SIGNALING PATHWAYS ACTIVATED BY NEUROTROPHIC FACTORS

Soluble and membrane embedded neurotrophic factors bind to specific re ceptors on responsive neurons and thereby initiate dramatic changes in the proliferation, differentiation, and survival of their target cell s. Recent studies have elucidated many of the intracellular pathways b y which neurotrophins and ciliary neurotrophic factor (CNTF) function to regulate gene expression and thereby achieve diverse biological res ponses. In this review we have focused particular attention on the imp ortance of the Ras-MAP kinase pathway for neurotrophin signaling, and the role of the Jak-STAT pathway for CNTF signaling. Characterization of the enzymes, linker proteins, and transcription factors that are se quentially activated in response to neurotrophic factors has provided significant insight into the mechanisms by which these agents elicit s pecific biological responses during normal development and into the ad aptive responses of mature neurons.