To survive, neurons and other eukaryotic cells must rapidly repair (seal) plasmalemmal damage. Such repair occurs by an accumulation of intracellular vesicles at or near the plasmalemmal disruption. Diacylglycerol (DAG)-dependent and cAMP-dependent proteins are involved in many vesicle trafficking pathways. Although recent studies have implicated the signaling molecule cAMP in sealing, no study has investigated how DAG and DAG-dependent proteins affect sealing. By means of dye exclusion to assess Ca(2+)-dependent vesicle-mediated sealing of transected neurites of individually identifiable rat hippocampal B104 cells, we now report that, compared to non-treated controls, sealing probabilities and rates are increased by DAG and cAMP analogs that activate PKC and Munc13-1 and PKA. Sealing is decreased by inhibiting DAG-activated novel protein kinase C isozymes (nPKC) and θ (nPKCθ) and Munc13-1, the PKC effector myristoylated alanine rich PKC substrate (MARCKS) or phospholipase C (PLC). DAG-increased sealing is prevented by inhibiting MARCKS or protein kinase A (PKA). Sealing probability is further decreased by simultaneously inhibiting nPKC, nPKCθ, and PKA. Extracellular Ca(2+), DAG, or cAMP analogs do not affect this decrease in sealing. These and other data suggest that DAG increases sealing through MARCKS and that nPKC, nPKCθ, and PKA are all required to seal plasmalemmal damage in B104 and likely all eukaryotic cells.