IMMUNOHISTOCHEMICAL ANALYSIS OF PRESENILIN-2 EXPRESSION IN THE MOUSE-BRAIN - DISTRIBUTION PATTERN AND COLOCALIZATION WITH PRESENILIN-1 PROTEIN

Missense mutations of presenilin 1 (PS-1) and presenilin 2 (PS-2) gene s cause the majority of early-onset familial forms of Alzheimer's dise ase (AD). We previously characterized the distribution of the PS-1 pro tein in the mouse brain by immunohistochemistry using an antibody dire cted against an epitope located in the large hydrophilic loop [Moussao ui, S., Czech, C., Pradier, L., Blanchard, V., Bonici, B., Gohin, M., Imperato, A. and Revah, F., Immunohistochemical analysis of presenilin 1 expression in the mouse brain, FEES Lett., 383 (1996) 219-222]. Sim ilarly, we now report the distribution pattern of PS-2 protein in the mouse brain. For these experiments we used a polyclonal antibody raise d against a synthetic peptide corresponding to the amino-acid sequence 7-24 of the predicted human PS-2 protein. The specificity of the anti body was evidenced by its ability to recognize PS-2 protein in immunop recipitation studies and by antigen-peptide competition. In the mouse brain, PS-2 protein was present in numerous cerebral structures, but i ts distribution in these structures did not correlate with their susce ptibility to AD pathology. In all examined structures of the gray matt er, PS-2 protein was concentrated in neuronal cell bodies but it was n ot detected in the glial cells of the white matter. The regional distr ibution pattern of PS-2 protein was almost identical to that of PS-1 p rotein. Moreover, PS-2 protein co-localized with PS-1 protein in a lar ge number of neuronal cell bodies. In terms of subcellular localizatio n, PS-2 immunostaining was present almost exclusively in neuronal cell bodies while PS-I immunostaining was also present in dendrites. This could be explained by the different epitopes of the antibodies and the known proteolytic processing of both presenilins in vivo [Tanzi, R.E. , Kovacs, D.M., Kim, T.-W., Moir, R.D., Guenette, S.Y. and Wasco, W., The presenilin genes and their role in early-onset familial Alzheimer' s disease, Alzheimer's disease Rev., 1 (1996) 91-98]. Within neuronal cell bodies, the immunostaining of PS-2 protein, as well as that of PS -1 protein, had a reticular and granular appearance. This suggests in agreement with previous observations on PS-1 and PS-2 in COS and H4 ce lls [Kovacs, D.M., Fausett, H.J., Page, K.J., Kim, T.-W., Moir, R.D., Merriam, D.E., Hollister, R.D., Hallmark, O.G., Mancini, R., Felsenste in, K.M., Hyman, B.T., Tanzi, R.E., Wasco, W., Alzheimer-associated pr esenilins 1 and 2: neuronal expression in brain and localization to in tracellular membranes in mammalian cells, Nature Med., 2 (1996) 224-22 9] that these proteins are situated in intracytoplasmic organelles, po ssibly the endoplasmic reticulum and the Golgi complex.