Immunological evidence that the β isoform of Ca²⁺/calmodulin‐dependent protein kinase IV is a cerebellar granule cell‐specific product of the CaM kinase IV gene

Abstract

Abstract Ca 2+ /calmodulin‐dependent protein kinase IV (CaM kinase IV) exists as two monomeric isoforms, α and β. In this study, we raised an antibody against the β isoform and provided immunohistochemical evidence for specific expression of the β isoform in cerebellar granule cells as a single gene‐derived translational product distinct from the α isoform. Immunohistochemical examination showed that the β‐immunoreactivity was confined to the nuclei of the cerebellar granule cells, in contrast to the more widespread immunoreactivity for the α isoform in both nuclei and cytoplasm of the cerebellar granule cells and many other neurons with dominant nuclear localization. In developing cerebella, the β‐immunoreactivity gradually appeared in the internal granule cells during the postnatal 2nd and 3rd weeks, while the α‐immunoreactivity had already appeared in the internal granule cells in the 1st postnatal week. Unlike the α isoform, β‐immunoreactivity was not detected in the Purkinje cells at any developmental stages. The differential expression of the α and β isoforms suggests that each isoform may be involved in different cerebellar functions.