A 21-KDA POLYPEPTIDE BELONGING TO A NEW FAMILY OF PROTEINS IS EXPRESSED IN THE GOLGI-APPARATUS OF NEURAL AND GERM-CELLS

We have isolated a full-length murine clone corresponding to the rat n euronal p1A75 partial cDNA (Sutcliffe, J. G., Milner, R. J., Shinnick, T. M., and Bloom, F, E. (1983) Cell 33, 671-682). It encodes a 185-re sidue polypeptide that displays 56% identity with p19, a protein selec tively expressed in the Golgi apparatus of neural cells (Saberan-Djone idi, D., Marey-Semper, I., Picart, R., Studler, J.-M., Tougard, C., Gl owinski, J., and Levi-Strauss, M. (1995) J. Biol. Chem. 270, 1888-1893 ). An antibody directed against the recombinant polypeptide allowed us to demonstrate the existence of the natural 21-kDa protein (p21) in b rain and its prominent juxtanuclear Golgi-like localization in culture d neurons. Ultrastructural observation of cultured neurons and analysi s of transfected COS cells revealed a specific labeling of the Gels ap paratus, suggesting, as for p19, the presence of a Gels targeting sign al in its primary sequence. Surprisingly, p21, which is much more stro ngly expressed in the olfactory epithelium than p19, is also present i n the Golgi complex of spermatocytes and in the flagellar middle piece of late spermatids.