TRANSPORT OF CAM KINASE ALONG PROCESSES ELICITED BY NEURONAL CONTACT EVOKES AN INHIBITION OF ARBORIZATION AND OUTGROWTH IN DROSOPHILA-MELANOGASTER CULTURED NEURONS

Transgenic Drosophila strains expressing an inhibitory peptide of Ca2/calmodulin dependent protein kinase II (CaM Kinase), or a constitutiv ely activated CaM kinase, show altered neuronal process morphology com pared to wild type in scanning electron microscopy (SEM) of cultured m ature neurons from embryonic neuroblasts. We observed significantly en hanced process growth in cells with inhibited enzyme, and reduced proc ess growth in cells with activated enzyme, suggesting that active CaM kinase is involved in the inhibition of neurite growth during developm ent. The subcellular distribution of CaM kinase in wild type neuronal cultures was determined using a gold particle labeling procedure which allowed the mapping of the enzyme directly in the scanning electron m icroscope (SEM). Before neuronal contact there was little labeling of processes, but after connections had been made the processes were heav ily labeled. Our results suggest that the major transport of CaM kinas e to the terminals does not occur until after or during the formation of neuronal connections when a functional synapse might be formed. Tak en together, these results suggest a target-dependent transport of the enzyme along processes and an inhibitory role for CaM kinase on neuri te branching. (C) 1996 Wiley-Liss, Inc.