IDENTIFICATION AND CHARACTERIZATION OF PORCINE NP-190, A NOVEL PROTEIN THAT IS SPECIFICALLY EXPRESSED IN THE AXONAL MEMBRANE DURING THE EMBRYONIC PERIOD

To identify and analyze the function of proteins expressed in the grow th cones, we have screened monoclonal antibodies raised against the pr eparation of the growth cone particles derived from fetal porcine brai ns and found a novel neuronal antigen, termed NP-190. Biochemical char acterization of NP-190 demonstrated that it was an integral membrane p rotein with an apparent molecular weight of 190 kDa and that it was ma inly expressed in fetal brains, Homologous antigens with molecular wei ghts of 200 and 170 kDa were also identified in the fetal brain extrac ts of chickens and rats, respectively. Immunoblot experiments of brain extracts from chickens and rats in various stages of development indi cated that the expression of NP-190 homologs was developmentally regul ated; it began to appear and increased in the embryonic stage, then de creased to very low level in the adult brains. Immunostaining of cultu red primary of neurons from the embryonic day 18 rat cerebral cortex d emonstrated that rat NP-190 homolog localized in the cell bodies, axon s and growth cones, but not in dendrites, Partial amino acid sequence analysis of affinity purified NP-190 from fetal porcine brains demonst rated that it was a novel protein, These results suggest that NP-190 p lays a distinct role in brain development.