24 KDA GTP-BINDING PROTEINS IN OPTIC NERVE DYNAMICS

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The vertebrate retina is the primary visual organ. Visual information collected by the retinal ganglion neurons is transmitted to the brain via axons which make up the myelinated optic nerve. This nerve, besides being of key importance in vision, also serves as an excellent system to investigate axonal transport of membranous organelles and precursors of plasma membranes and synaptic vesicles. It has recently been shown that the severed optic nerve can, at least in part, regenerate along a peripheral nerve graft and reach the correct region of the brain, thus serving as an excellent system to examine the requirements for CNS regeneration. Finally, there is evidence of optic nerve pathology in Alzheimer's disease. For several years we have been investigating the rapid axonal transport machinery in rabbit, and more recently in bovine optic nerve. We have very recently characterized a group of low molecular weight GTP binding proteins associated with optic nerve rapid transport vesicles and potential target membranes, i.e. synaptic plasma membrane and synaptic vesicles. In view of the recent evidences defining an important role of this protein class in secretion and vesicular transport, we have proposed a systematic investigation of the structure, biosynthesis, localization and function of these low molecular weight GTP binding proteins. We will particularly localize these proteins in the developing retina and optic nerve. We will employ methods of biochemistry, tissue culture, immunocytochemistry and video intensification microscopy in these investigations. We feel that these studies will, hopefully, shed new light on the mechanism of rapid axonal transport in adult and developing optic nerve which may have significant implications for CNS development and potentially, regeneration.