DIFFERENTIAL SUBCELLULAR-LOCALIZATION OF NEURAL ISOFORMS OF THE CATALYTIC SUBUNIT OF CALMODULIN-DEPENDENT PROTEIN PHOSPHATASE (CALCINEURIN)IN CENTRAL-NERVOUS-SYSTEM NEURONS - IMMUNOHISTOCHEMISTRY ON FORMALIN-FIXED PARAFFIN SECTIONS EMPLOYING ANTIGEN RETRIEVAL BY MICROWAVE IRRADIATION

We examined the immunohistochemical distribution of the two mammalian isoforms of calcineurin catalytic subunits, An and A beta, in central nervous system (CNS) tissues of cows, rats, and humans. Cryostat secti ons and paraffin sections of paraformaldehyde-fixed tissues were stain ed with antipeptide antibodies for each isoform. The same localization pattern was observed in both cryostat and paraffin sections. In the l atter, the intensity of the staining was dramatically enhanced by micr owave irradiation. Calcineurin isoforms were localized in a variety of nerve cells but not in neuroglial cells. Their differential expressio n as the A alpha isoform in the nucleus and the A beta isoform in the cytoplasm was present in a variety of CNS nerve cells, most distinctiv ely in Purkinje cells of the cerebellum and pyramidal cells of the cer ebrum, irrespective of species. These results suggest that each isofor m has distinct intracellular sites of action in CNS neurons and that t he phenomenon has been conserved during mammalian evolution.