Regulation of neurite outgrowth by G(i/o) signaling pathways

Neurogenesis is a long and winding journey. A neural progenitor cell migrates long distances, differentiates by forming a single axon and multiple dendrites, undergoes maturation, and ultimately survives. The initial formation of neurites during neuronal differentiation, commonly referred to as "neurite outgrowth," can be induced by a large repertoire of signals that stimulate an array of receptors and downstream signaling pathways. The G(i/o) family of heterotrimeric G-proteins are abundantly expressed in the brain and enriched at neuronal growth cones. Recent evidence has uncovered several G(i/o)-coupled receptors that induce neurite outgrowth and has begun to elucidate the underlying molecular mechanisms. Emerging data suggests that signals from several G(i/o)-coupled receptors converge at the transcription factor STAT3 to regulate neurite outgrowth and at Rac1 and Cdc42 to regulate cytoskeletal reorganization. Physiologically, signaling through G(i/o)-coupled cannabinoid receptors is critical for pro percentral nervous system development. As the mechanisms by which G(i/o)-coupled receptors regulate neurite outgrowth are clarified, it is becoming evident that modulating signals from G(i/o) and their receptors has great potential for the treatment of neurodegenerative diseases.