The carboxyl terminus of VEGFR-2 is required for PKC-mediated down-regulation

Mol Biol Cell. 2005 Apr;16(4):2106-18. doi: 10.1091/mbc.e04-08-0749. Epub 2005 Jan 26.

Abstract

Vascular endothelial growth factor receptor-2 (VEGFR-2/Flk-1) is a receptor tyrosine kinase (RTK) whose activation regulates angiogenesis. The regulatory mechanisms that attenuate VEGFR-2 signal relay are largely unknown. Our study shows that VEGFR-2 promotes phosphorylation of c-Cbl, but activation, ubiquitylation, and down-regulation of VEGFR-2 are not influenced by c-Cbl activity. A structure-function analysis of VEGFR-2 and pharmacological approach revealed that down-regulation of VEGFR-2 is mediated by a distinct mechanism involving PKC. A tyrosine mutant VEGFR-2, defective in PLC-gamma1 activation underwent down-regulation efficiently in response to ligand stimulation, suggesting that activation of classical PKCs are not involved in VEGFR-2 down-regulation. Further studies showed that the ectodomain of VEGFR-2 is dispensable for PKC-dependent down-regulation. Progressive deletion of the carboxyl-terminal domain showed that at least 39 amino acids within the carboxyl-terminal domain, immediately C-terminal to the kinase domain, is required for efficient PKC-mediated down-regulation of VEGFR-2. Mutation of serine sites at 1188 and 1191, within this 39 amino acid region, compromised the ability of VEGFR-2 to undergo efficient ligand-dependent down-regulation. Altogether the results show that the regulatory mechanisms involved in the attenuation of VEGFR-2 activation is mediated by nonclassical PKCs and the presence of serine sites in the carboxyl terminal of VEGFR-2.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Cell Line
  • Down-Regulation* / drug effects
  • Enzyme Activation / drug effects
  • ErbB Receptors / metabolism
  • Humans
  • Ligands
  • Phospholipase C gamma
  • Protein Kinase C / metabolism*
  • Proto-Oncogene Proteins / metabolism
  • Proto-Oncogene Proteins c-cbl
  • Serine / genetics
  • Serine / metabolism
  • Swine
  • Tetradecanoylphorbol Acetate / analogs & derivatives
  • Tetradecanoylphorbol Acetate / pharmacology
  • Type C Phospholipases / metabolism
  • Ubiquitin-Protein Ligases / metabolism
  • Vascular Endothelial Growth Factor Receptor-2 / genetics
  • Vascular Endothelial Growth Factor Receptor-2 / metabolism*

Substances

  • Ligands
  • Proto-Oncogene Proteins
  • Serine
  • phorbolol myristate acetate
  • Proto-Oncogene Proteins c-cbl
  • Ubiquitin-Protein Ligases
  • ErbB Receptors
  • Vascular Endothelial Growth Factor Receptor-2
  • Protein Kinase C
  • Type C Phospholipases
  • Phospholipase C gamma
  • Tetradecanoylphorbol Acetate