A protein kinase Cε-anti-apoptotic kinase signaling complex protects human vascular endothelial cells against apoptosis through induction of Bcl-2

Endothelial cell apoptosis is associated with vascular injury and predisposes to atherogenesis. Endothelial cells express antiapoptotic genes including Bcl-2, Bcl-XL and survivin, which also contribute to angiogenesis and vascular remodeling. We report a central role for protein kinase C epsilon(PKC epsilon) in the regulation of Bcl-2 expression and cytoprotection of human vascular endothelium against apoptosis. Using myristoylated inhibitory peptides, a predominant role for PKC epsilon in vascular endothelial growth factor-mediated endothelial resistance to apoptosis was revealed. Immunoblotting of endothelial cells infected with an adenovirus expressing a constitutively active form of PKC epsilon (Adv-PKC epsilon-CA) or control Adv-beta-galactosidase demonstrated a 3-fold, PKC epsilon-dependent increase in Bcl-2 expression, with no significant change in Bcl-X-L, Bad, Bak, or Bax. The induction of Bcl-2 inhibited apoptosis induced by serum starvation or etoposide, and PKC epsilon activation attenuated etoposide-induced caspase-3 cleavage. The functional role of Bcl-2 was confirmed with Bcl-2 antagonist HA-14-1. Inhibition of phosphoinositide 3-kinase attenuated vascular endothelial growth factor-induced protection against apoptosis, and this was rescued by overexpression of constitutively active PKC epsilon, suggesting PKC epsilon acts downstream of phosphoinositide 3-kinase. Co-immunoprecipitation studies demonstrated a physical interaction between PKC epsilon and Akt, which resulted in formation of a signaling complex, leading to optimal induction of Bcl-2. This study reveals a pivotal role for PKC epsilon in endothelial cell cytoprotection against apoptosis. We demonstrate that PKC epsilon forms a signaling complex and acts co-operatively with Akt to protect human vascular endothelial cells against apoptosis through induction of the anti-apoptotic protein Bcl-2 and inhibition of caspase-3 cleavage.