CALCIUM CALMODULIN-DEPENDENT PROTEIN-KINASE-II EXPRESSION IN MOTOR-NEURONS - EFFECT OF AXOTOMY/

Although Ca2+/calmodulin-dependent (CaM) protein kinase II isoforms ar e present in the nervous system in high amounts, many aspects of in vi vo expression, localization, and function remain unexplored, During de velopment, CaM kinase II alpha and II beta are differentially expresse d, Here, we examined CaM kinase II isoforms in Sprague-Dawley rat scia tic motor neurons before and after axotomy. We cut the L4-5 spinal ner ves unilaterally and exposed the proximal nerve stumps to a fluoroprob e, to retrogradely label the neurons of origin, Anti-CaM kinase II bet a antibody showed immunoreactivity in motor neurons, which decreased t o low levels by 4 days after axotomy, We found a similar response by i n situ hybridization with riboprobes, The decrease in expression of mR NA and protein was confined to fluorescent motor neurons, For CaM kina se II alpha, in sib hybridization showed that the mRNA was in sciatic motor neurons, with a density unaffected by axotomy, However, these ne urons were also enlarged, suggesting an up-regulation of expression, N orthern blots confirmed an mRNA increase, We were unable to find CaM k inase II alpha immunoreactivity before or after axotomy in sciatic mot or neuron cell bodies, suggesting that CaM kinase II alpha is in the a xons or dendrites, or otherwise unavailable to the antibody, Using rat s with crush lesions, we radiolabeled axonal proteins being synthesize d in the cell body and used two-dimensional polyacrylamide gel electro phoresis with Western blots to identify CaM kinase II alpha as a compo nent of slow axonal transport, This differential regulation and expres sion of kinase isoforms suggests separate and unique intracellular rol es, Because we find CaM kinase II beta down-regulates during axonal re growth, its role in these neurons may be related to synaptic transmiss ion, CaM kinase II alpha appears to support axonal regrowth, (C) 1997 John Wiley & Sons, Inc.