Distribution of calcium/calmodulin-dependent kinase 2 in the brain of Apteronotus leptorhynchus

Antibodies directed against the mammalian alpha and beta subunits of calciu m/calmodulin-dependent kinase 2 (CaMK2) and brain dissection were used for immunoblot analysis of these proteins in various brain regions of Apteronot us leptorhynchus. Western blots revealed that the CaMK2 alpha antibody labe led a single band of the expected molecular mass (similar to 50 kDa) for th is enzyme in rat cortex and electric fish brain. CaMK2 alpha was enriched i n fish forebrain and hypothalamus and also strongly expressed in midbrain s ensory areas. Western blots revealed that CaMK2 beta antibodies labeled ban ds in an appropriate molecular mass range (similar to 58-64 kDa) for this e nzyme in mammalian cortex and electric fish brain. However, a higher molecu lar mass band (similar to 80 kDa) was also labeled; because all these bands were eliminated by preadsorbtion with the CaMK2-derived peptide antigen, t hey may all represent CaMK2 beta-like isoforms. We mapped the brain distrib ution of CaMK2 isoforms with emphasis on the electrosensory system. CaMK2 a lpha was present at high density in dorsal forebrain, hypothalamic nuclei, torus semicircularis, and tectum. It was also enriched in discrete fiber tr acts in forebrain, diencephalon, and rhombencephalon. CaMK2 beta-like isofo rms were enriched in ventral forebrain, hypothalamic nuclei, torus semicirc ularis and the reticular formation. Unlike CaMK2 alpha, CaMK2 beta-like iso forms were predominantly present in cell bodies and rarely found in fiber t racts or neuropil. In the electrosensory lateral line lobe, CaMK2 alpha was restricted to specific feedback fibers, i.e., tractus stratum fibrosum and its terminal field in the ventral molecular layer. In contrast, CaMK2 beta -like isoforms were enriched in somata and dendrites of pyramidal cells and granular interneurons. J. Comp. Neurol. 408:171-203, 1999. (C) 1999 Wiley- Liss, Inc.