Nuclear Localization of the δ Subunit of Ca2+/Calmodulin‐Dependent Protein Kinase II in Rat Cerebellar Granule Cells

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Abstract
: To examine the physiological roles of the δ subunit of Ca2+/calmodulin‐dependent protein kinase ∥ (CaM kinase ∥δ) in brain, we examined the localization of CaM kinase ∥δ in the rat brain. A specific antibody to CaM kinase ∥δ1‐δ4 isoforms was prepared by immunizing rabbits with a synthesized peptide corresponding to the unique carboxyl‐terminal end of these isoforms. The prepared antibody did not recognize the α, β, and γ subunits, which were each overexpressed in NG108‐15 cells. Immunoblot analysis on various regions and the nuclear fractions from rat brains suggested that some isoforms of CaM kinase ∥δ1‐δ4 were abundant in the nucleus in the cerebellum. Total RNA from the cerebellum was analyzed by RT‐PCR with a primer pair from variable domain 1 to variable domain 2. We detected the three PCR products δ3.1, δ3.4, and δ3 that contained the nuclear localization signal. These CaM kinase ∥δ3 isoforms were localized in the nuclei in transfected NG108‐15 cells. Immunohistochemical study suggested the existence of these isoforms in the nuclei in cerebellar granule cells. These results suggest that CaM kinase ∥δ3 isoforms are involved in nuclear Ca2+ signaling in cerebellar granule cells.

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