J Biol Chem, Vol. 273, Issue 7, 3909-3914, February 13, 1998

A 21-kDa Polypeptide Belonging to a New Family of Proteins Is Expressed in the Golgi Apparatus of Neural and Germ Cells

Délara Sabéran-Djoneidi, Renée Picart^¶, Denise Escalier, Michèle Gelman, Alain Barret^¶, Claude Tougard^¶, Jacques Glowinski, and Matthieu Lévi-Strauss

From the  INSERM U. 114 Chaire de Neuropharmacologie and ^¶ INSERM U. 36 Groupe de Biologie de la Cellule Neuroendocrine, Collège de France, 11 place Marcelin-Berthelot, 75005 Paris, France and  INSERM U. 25, Hôpital Necker, 161 rue de Sèvres, 75743 Paris Cedex 15, France

We have isolated a full-length murine clone corresponding to the rat neuronal 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-residue polypeptide that displays 56% identity with p19, a protein selectively expressed in the Golgi apparatus of neural cells (Sabéran-Djoneidi, D., Marey-Semper, I., Picart, R., Studler, J.-M., Tougard, C., Glowinski, J., and Lévi-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 brain and its prominent juxtanuclear Golgi-like localization in cultured neurons. Ultrastructural observation of cultured neurons and analysis of transfected COS cells revealed a specific labeling of the Golgi apparatus, suggesting, as for p19, the presence of a Golgi targeting signal in its primary sequence. Surprisingly, p21, which is much more strongly expressed in the olfactory epithelium than p19, is also present in the Golgi complex of spermatocytes and in the flagellar middle piece of late spermatids.