CELL AND TISSUE DISTRIBUTION AND DEVELOPMENTAL-CHANGE OF NEURON-SPECIFIC 14 KDA PROTEIN (PHOSPHONEUROPROTEIN-14)

In the present paper, the distribution of a neuron-specific phosphoneu roprotein 14 (PNP 14) in cell and tissue was investigated in detail by the immunoblot method using affinity-purified antibody against this p rotein. The immunoblot of the supernatant fractions of various tissue homogenates of rat clearly demonstrated that PNP 14 was enormously ric h in the brain. The content in rat brain was as much as 0.1% of the ho mogenate. The immunocytochemical study showed that the protein was loc alized at nerve endings in the cerebellum. Existence of the protein wa s also comfirmed in cultured neuronal cells from postnatal rat midbrai n, but not in glial cells. Examination of subcellular localization of PNP 14 indicates that the protein was present in synaptic plasma membr anes and synaptic supernatant fractions, but not in synaptic vesicles. During the development of rat brain, PNP 14 came into existence after birth and it's amount linearly increased to a maximum at 21-28 days a fter birth. The content of the protein then remained at the same level for more than 10 months. We concluded that this protein is neuron spe cific and supposed that it may be involved in neuronal formation and f unction.