Obligatory role of protein kinase Cbeta and MARCKS in vesicular trafficking in living neurons.

Neurotransmitter release from neurons involves both vesicular trafficking and subsequent fusion of synaptic vesicles with the plasma membrane. The mechanisms involving the formation and fusion of vesicles that allow the exocytotic release of transmitters are understood well. Little is known, however, about the signaling mechanism involved in the trafficking of vesicles along the neurites. In this study, we used real-time confocal microscopy to search for evidence that vesicular trafficking in neurons requires the activation of protein kinase Cbeta (PKCbeta) and the myristoylated alanine-rich C kinase substrate (MARCKS) signaling pathway. Dopamine-beta-hydroxylase fused to green fluorescent protein has been used to trace vesicular movement. Angiotensin II, an established neuromodulatory hormone, stimulates translocation of green fluorescent protein-dopamine-beta-hydroxylase vesicles from the cell body to neurites. This translocation was blocked by an antisense oligonucleotide to PKCbeta and MARCKS. Stimulation of PKC by other means, such as phorbol-12-myristate-13-acetate or carbachol, also resulted in the redistribution of fluorescence in a manner similar to that observed for angiotensin II. These observations demonstrate that PKCbeta-MARCKS signaling may be a general mechanism for the stimulation of vesicular trafficking in brain neurons.