Visualization of peptide secretory vesicles in living nerve cells.

Analysis of real-time movements of peptidergic vesicles in live neurons provides insight into molecular mechanism(s) supporting the activity-dependent secretion of neurotrophins and neuropeptides. We examined the effect of overexpression of exogenous peptides comprising of the cytoplasmic tail sequence of vesicular carboxypeptidase E (CPE), proposed to be involved in the mechanism of trafficking of peptidergic secretory vesicles, in live hippocampal neurons. E16 rat hippocampal neurons were transfected with the peptidergic vesicle markers, CPE C-terminally tagged with red or green fluorescent protein, or brain-derived neurotrophic factor (BDNF) tagged with green fluorescent protein, and grown on dishes specialized for real-time live cell visualization. Movements of peptidergic vesicles were imaged in a temperature-controlled chamber on a confocal inverted microscope and analyzed with respect to their velocity, displacement distance, and processivity.