Characterization of mouse neuronal Ca2+/calmodulin kinase II inhibitor α

We have overexpressed an 8.5-kDa mouse Ca2+/calmodulin kinase II inhibitor α protein (mCaMKIINα) in Escherichia coli and demonstrate that the recombinant protein is a potent inhibitor of Ca2+/calmodulin kinase II (CaMKII) in vitro. However, antibodies raised against recombinant mCaMKIINα react with an ∼ 37-kDa protein present in mouse brain. The pattern of expression of the ∼ 37-kDa protein is similar to that of mCaMKIINα mRNA as both are expressed in normal but not Japanese encephalitis virus (JEV)-infected mouse brain. Subcellular localization studies indicate that the ∼ 37-kDa protein is present in the post-synaptic density (PSD) where mCaMKIIα is known to perform key regulatory functions. We conclude that the ∼ 37-kDa protein identified in this study is mCaMKIINα and its localization in the PSD indicates a novel role for this protein in the regulation of neuronal CaMKIIα.