Biphasic and directed translocation of protein kinase Cα inside cultured endothelial cells before migration.

Mechanical wounding of an endothelial monolayer induces an immediate Ca(2+) wave. Several hours later, the denuded area is covered by endothelial cells (ECs) that migrate to the wound. This migration process is closely related to protein kinase Cα (PKCα), a Ca(2+)-dependent protein that translocates from the cytosol to the cell membrane. Because the cells adjacent to the wounded area are the first to migrate into the wound, we investigated whether a mechanical wound immediately induces PKCα translocation in adjacent cells. We monitored Ca(2+) dynamics and PKCα translocation simultaneously using fluorescent microscopy. For this simultaneous observation, we used Fura-2-acetoxymethyl ester to visualize Ca(2+) and constructed a green fluorescent protein-tagged fusion protein to visualize PKCα. Mechanical wounding of the endothelial monolayer induced an immediate Ca(2+) wave in cells adjacent to the wounded cells before their migration. Almost concurrently, PKCα in the neighboring cells translocated to the cell membrane, then accumulated at the periphery near the wounded cell. This report is the first description of this biphasic and directed translocation of PKCα in cells before cell migration. Our results may provide new insights into the directed migration of ECs.