Developmental and regional expression of multifunctional Ca2+/calmodulin-dependent protein kinase isoforms in rat brain.
Multifunctional Ca2+/calmodulin-dependent protein kinase (CaM kinase) participates in diverse calcium signaling pathways in neurons. The alpha- and beta-CaM kinase isoforms are neuron-specific and highly abundant in rat brain. The variable domain of CaM kinase is a potential site for the generation of isoform diversity by alternative spicing of its N- and/or C-terminal segments. We used specific PCR primers which span the variable domain of either alpha- or beta-CaM kinase and isolated three new isoforms from rat brain, namely alpha B-, beta e- and beta'e-CaM kinase. alpha beta-CaM kinase contains 11 amino acids, likely inserted by alternative splicing, at the C-terminal segment of the variable domain. This insertion introduces a nuclear localization signal (NLS) that targets alpha B-CaM kinase to the nucleus of transfected cells; alpha-CaM kinase is excluded from the nucleus. The mRNA and the protein corresponding to this isoform are detected only in the diencephalon/midbrain regions. We have also identified two alternatively spliced isoforms of beta-CaM kinase that lack the 24 amino acid sequence at the N-terminal segment of the variable domain. Alternative splicing of these two isoforms occurs with a three base pair shift of the 3'-splice site. Our analysis shows that these new beta-CaM kinase isoforms are expressed primarily in early developmental stages, and we therefore term them beta e - (embryonic) and beta' e-CaM kinase. Recombinant alpha B-, beta e and beta' e-CaM kinase expressed in COS-7 cells exhibit characteristic Ca2+/calmodulin-dependent protein kinase activity and autophosphorylation.
D000375:Aging / Q000378:metabolism*; D017398:Alternative Splicing; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000201:enzymology*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D004622:Embryo, Mammalian / Q000378:metabolism; D005314:Embryonic and Fetal Development; D007527:Isoenzymes / Q000378:metabolism*; D015335:Molecular Probes / Q000235:genetics; D008969:Molecular Sequence Data; D051381:Rats; D017207:Rats, Sprague-Dawley
D007527:Isoenzymes; D015335:Molecular Probes; D017871:Calcium-Calmodulin-Dependent Protein Kinases