title: Protein kinase C and downstream signaling pathways in a three-dimensional model of phorbol ester-induced angiogenesis.
abstract: Angiogenesis, a critical process in both health and disease, is mediated by a number of signaling pathways. Although proangiogenic stimuli, including vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and the phorbol ester phorbol-12 myristate-13 acetate (PMA) are known to promote blood vessel formation, their downstream targets are ill defined. We sought to investigate the signaling pathways required for vessel assembly by utilizing a three-dimensional collagen matrix in which human umbilical vein endothelial cells (HUVECs) form tubular structures. Our data show that PMA is sufficient for the induction of angiogenesis, and that protein kinase C (PKC) is necessary for this process. Evaluation of PKC isoforms alpha and sigma revealed that these proteins are uniquely regulated. Characterization of an additional PMA target, protein kinase D (PKD) demonstrated that this enzyme becomes phosphorylated in HUVECs, and may therefore be involved in proangiogenic signaling. Further examination of downstream effectors of PKC showed that extracellular signal-regulated kinase (ERK) is critical for angiogenesis, and is accordingly phosphorylated in response to PMA. Surprisingly however, phosphorylation of ERK is independent of PKC activity. In addition, we show that the PKC target sphingosine kinase (SPK) is required for vessel formation. These findings illustrate the complexities of blood vessel formation, and suggest that activators utilize multiple independent pathways to invoke a complete angiogenic response.
authors.affiliation: Vascular Biology Center, Medical College of Georgia, Augusta, Georgia 30912, USA.
authors.forename: Caroline J
authors.initials: CJ
authors.lastname: Taylor
authors.forename: Kouros
authors.initials: K
authors.lastname: Motamed
authors.forename: Brenda
authors.initials: B
authors.lastname: Lilly
mesh_terms: D018929:Cell Culture Techniques; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D004789:Enzyme Activation; D005109:Extracellular Matrix / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008954:Models, Biological; D018919:Neovascularization, Physiologic / Q000187:drug effects*; D011494:Protein Kinases / Q000378:metabolism*; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D013997:Time Factors; D014471:Umbilical Veins / Q000166:cytology
chemical_list: D011494:Protein Kinases; C475887:protein kinase C kinase; D020928:Mitogen-Activated Protein Kinases; D013755:Tetradecanoylphorbol Acetate