THE NEURONAL CYTOSKELETON - STRUCTURAL, FUNCTIONAL AND DYNAMIC ASPECTS

The cytoskeleton of practically every type of cell is constituted by 3 types of filaments: microfilaments, microtubules and intermediate filaments. The latter are cell-type specific and are represented in neurons by neurofilaments accompanied by other intermediate filaments, which have recently been described and whose nature depends on the period of development and on the neuronal type. Numerous studies demonstrate that many proteins are associated with microfilaments and microtubules and that they are responsible not only for the structure of the lattices but also for their function and dynamics. Moreover, these proteins can link one type of filament to another, and the network thus constituted, to the plasmic membrane and probably also to the nuclear membrane. The neuronal cytoskeleton is not static; it has, of course, a very important role in the maintenance of the structural integrity of the neuron, but it is also the promotor of axonal growth, the substratum against which many organelles move and thus has an essential role in axonal transport. In a few neuropathies chosen as examples for a disturbed axonal transport, abnormal bundles of filaments are observed; they are probably the end product of a primary disorder which has still to be analyzed.