Tissue Distribution of Calmodulin-Kinase II Subunits

The subunit structure of native CaM-kinase II isozymes and the expression of subunits at the level of mRNA have not been studied in detail in tissues other than brain, where the a- and (3-subunit mRNA is enriched compared to 8- and 7-subunit mRNA (Tobimat-su and Fujisawa, 1989). In brain, a-, p-, and P -subunits are differentially expressed both regionally and devel-opmentally (Kelly et al., 1987 Tobimatsu and Fujisawa, 

Based on Northern analysis, skeletal muscle has been reported to express primarily p-, 8-, and 7-subunit mRNA, whereas cardiac muscle, smooth muscles, and other peripheral organs appear to express 8- and 7-subunits (Tobimatsu and Fujisawa, 

RT-PCR analysis of mRNA from various tissue sources indicates that the full-sized 8-subunit is expressed only in brain (Schworer et al., 1993). Therefore, the reported distribution of the 8-subunit mRNA in peripheral tissues reflects the differential distribution of the smaller 82, 83 and 84 variants. For example, the RT-PCR analysis indicates that aortic smooth muscle expresses 82 and 83, cardiomyocytes primarily 83, and skeletal muscle the 84-isoforms (Schworer et al., 1993). 

HAROLD A. SINGER, S. THOMAS ABRAHAM. AND CHARLES M. SCHWORER 

unpublished observations). Expression of varying sized 8-subunit variants has been documented at the protein level in rat brain and aortic medial smooth muscle extracts by immunoblotting with an antipeptide antibody (CK2-Delta) that specifically recognizes 

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