Protein kinase Cα and sphingosine 1-phosphate-dependent signaling in endothelial cell

Protein kinase C (PKC)-mediated signal transduction pathways convert extracellular stimulation into a variety of cellular functions. However, the role of various PKC isoforms in sphingosine 1-phosphate (S1P)-stimulated endothelial cells is not well understood. PKCα and PKCɛ activity are increased in endothelial cell cultures, and S1P receptor transfection studies indicate S1P3 stimulates PKCα and S1P1 leads to PKCɛ activity. Infection of endothelial cells with dominant negative (DN)PKCα adenovirus reduces cell migration and greatly inhibits morphogenesis in cells stimulated with S1P. This effect is specific to PKCα, as infection with DN PKCɛ does not alter either migration or morphogenesis. The PKC-specific chemical inhibitor GF109203X also inhibits these two responses. Infection of endothelial cells with dominant negative PKCα reduces S1P-induced calcium rise. This maximal rise requires calcium uptake, but it does not require enzymatic activity of the kinase. Pretreatment of these cells with the PKC-specific inhibitor GF109203X does not inhibit S1P-induced calcium rise. S1P-induced morphogenesis but not cell migration is critically dependent on extracellular calcium. Pretreatment of endothelial cells with phorbol 12-myristate 13-acetate for 5 min abolishes S1P-stimulated rise in calcium but had little or no effect on migration. The PMA-inhibited calcium rise can be prevented by PKC inhibitor or infection with dominant negative PKCα.