A 19-KDA PROTEIN BELONGING TO A NEW FAMILY IS EXPRESSED IN THE GOLGI-APPARATUS OF NEURAL CELLS

The mouse 8.5 mRNA encodes a 171-residue novel protein which displays a highly significant similarity with the product of the previously cha racterized neuronal p1A75 cDNA (Sutcliffe, J. G., Milner, R. J., Shinn ick, T. M., and Bloom, F. E. (1983) Cell 33, 671-682). Northern blot a nd in situ hybridization experiments indicated that the 8.5 mRNA is sp ecifically expressed in neural and neuroendocrine tissues. An affinity -purified antibody directed against the recombinant 8.5 protein demons trated the existence of the 19-kDa natural protein in brain and eviden ced its prominent juxtanuclear Golgi-like localization in cultured neu rons. Ultrastructural analysis of the same preparation revealed a spec ific labeling of all the Golgi saccules and of some vesicles in the Go lgi zone. In transfected COS cells, the exogenous protein was also det ected in the Golgi area, indicating, therefore, the presence of a Golg i targeting signal in its primary sequence.