Intracellular mechanisms of axon growth induction by CAMs and integrins: some unresolved issues

Integrins and cell adhesion molecules (CAMs) are important neuronal receptors mediating substrate-induced axon growth. Signaling of axon growth through these receptors involves both regulation of tyrosine phosphorylation and transient increases in intracellular Ca2+. Many of the details concerning these signal transduction events and mechanisms through which they regulate effectors of axon growth are poorly understood. This review discusses some of the gaps in our current knowledge, with suggestions on approaches to closing these gaps. Emphasis is on the role of tyrosine phosphatases in the regulation of axon growth, the origin and nature of Ca2+ signals produced by stimulation of CAMs and integrins, and possible links of these two pathways to cytoskeletal rearrangements and directed addition of plasma membrane.