Calcium and polyphosphoinositide control of cytoskeletal dynamics.

Dynamic alterations in the structure of the neuronal cytoskeleton are necessary for axonal growth and guidance during development and may also be involved in modulation of synaptic function. Recent evidence suggests that the structural and mechanochemical properties of the cytoskeletal protein, actin, are critical to our understanding of neuronal motility and cytoskeletal plasticity. Regulatory proteins that control actin polymerization, network organization and actin filament--membrane interactions have been described in non-neuronal and neuronal cell types. Many of these proteins are activated by increases in intracellular calcium. Recent results also suggest that receptor-mediated changes in polyphosphoinositide turnover may be involved in the control of cell structure. Interestingly, two major actin-binding proteins found in brain, gelsolin and profilin, specifically interact with phosphatidylinositol 4,5-bisphosphate, and may themselves play a role in regulating phosphoinositide turnover.