Neuronal protein NP185 in avian and murine cerebellum: expression during development and evidence for its presence in nerve endings.

The neuronal protein NP185 is a neural tissue-specific protein isolated from clathrin-coated vesicles in brain. Using 8G8, a monoclonal antibody (MAb) characterized in our laboratory, we studied the expression and distribution of neuronal protein NP185 in developing avian cerebellum and in mature murine cerebellum. Furthermore, we compared these parameters to that of synapse-specific neuronal protein, synaptophysin, and an axon-specific (i.e., non-synaptic) neuronal protein, neurofilament NF68. We found that NP185 expression temporally and spatially corresponds to avian cerebellar synaptogenesis. In addition, NP185 distribution parallels synaptophysin distribution throughout development, while differing from that of either unassembled or filamentous forms of NF68. The evidence also suggests that embryonic NP185 expression coincides with synaptogenesis, and that NP185 remains concentrated in the terminal boutons of mature neurons. The synapse specificity of NP185 and the recent biochemical properties reported for this protein support the postulate that this molecule may trigger synaptic events and distinguish structurally and functionally active synapses.