Requirement for protein kinase C theta for cell cycle progression and formation of actin stress fibers and filopodia in vascular endothelial cells

Activation of the protein kinase C (PKC) family with phorbol esters induces endothelial proliferation and angiogenesis, but which of the events that constitute angiogenesis are affected by individual members of the PMC family is unknown. In rat capillary endothelial (BCE) cells, serum stimulation increased expression of a single PKC isoenzyme, PKC theta, and its translocation to the periphery. Conditional overexpression of a dominant-negative mutant of PKC theta markedly inhibited RCE proliferation, as well as closure of a ''wound'' by RCE migration and formation of capillary rings and tubules in vitro. PKC theta inhibition delayed the endothelial cell cycle at the G(2)/M phase and prevented formation of actin stress fibers and filopodia but not lamellipodia. The defect in cell morphology and wound closure in PKC theta-kn cells was reversed by overexpressing kinase-active PKC theta, indicating that these RCE functions depend upon PKC theta substrates. Thus, PKC theta is required for multiple processes essential for angiogenesis and wound repair, including endothelial mitosis, maintenance of a normal actin cytoskeleton, and formation of an enclosed tube.