title: A protein kinase Cepsilon-anti-apoptotic kinase signaling complex protects human vascular endothelial cells against apoptosis through induction of Bcl-2.
abstract: Endothelial cell apoptosis is associated with vascular injury and predisposes to atherogenesis. Endothelial cells express anti-apoptotic genes including Bcl-2, Bcl-XL and survivin, which also contribute to angiogenesis and vascular remodeling. We report a central role for protein kinase Cepsilon (PKCepsilon) in the regulation of Bcl-2 expression and cytoprotection of human vascular endothelium against apoptosis. Using myristoylated inhibitory peptides, a predominant role for PKCepsilon 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 PKCepsilon (Adv-PKCepsilon-CA) or control Adv-beta-galactosidase demonstrated a 3-fold, PKCepsilon-dependent increase in Bcl-2 expression, with no significant change in Bcl-XL, Bad, Bak, or Bax. The induction of Bcl-2 inhibited apoptosis induced by serum starvation or etoposide, and PKCepsilon 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 PKCepsilon, suggesting PKCepsilon acts downstream of phosphoinositide 3-kinase. Co-immunoprecipitation studies demonstrated a physical interaction between PKCepsilon and Akt, which resulted in formation of a signaling complex, leading to optimal induction of Bcl-2. This study reveals a pivotal role for PKCepsilon in endothelial cell cytoprotection against apoptosis. We demonstrate that PKCepsilon 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.
authors.affiliation: Bywaters Center for Vascular Inflammation and Histopathology Section, Imperial College London, Hammersmith Hospital, London, W12 ONN United Kingdom.
authors.forename: Rivka
authors.initials: R
authors.lastname: Steinberg
authors.forename: Olivier A
authors.initials: OA
authors.lastname: Harari
authors.forename: Elaine A
authors.initials: EA
authors.lastname: Lidington
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Boyle
authors.forename: Mahrokh
authors.initials: M
authors.lastname: Nohadani
authors.forename: Allen M
authors.initials: AM
authors.lastname: Samarel
authors.forename: Motoi
authors.initials: M
authors.lastname: Ohba
authors.forename: Dorian O
authors.initials: DO
authors.lastname: Haskard
authors.forename: Justin C
authors.initials: JC
authors.lastname: Mason
mesh_terms: D017209:Apoptosis; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism*; D004789:Enzyme Activation; D006801:Humans; D051744:Protein Kinase C-epsilon / Q000737:chemistry / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D015398:Signal Transduction; D014471:Umbilical Veins / Q000166:cytology / Q000378:metabolism