Protein kinase Cepsilon may act as EGF-inducible scaffold protein for phospholipase Cgamma1.
Phospholipase Cgamma1 (PLCgamma1) represents a major downstream signalling component of the epidermal growth factor (EGF) receptor (EGFR) and is activated by tyrosine phosphorylation. Here we show for the first time that cellular knockdown of protein kinase Cepsilon (PKCepsilon) leads to decreased activation of PLCgamma1 by EGF and that EGF induces tyrosine phosphorylation of PKCepsilon as well as association of PKCepsilon with both EGFR and PLCgamma1. Using several mutants, co-immunoprecipitation and phosphopeptide-based pull-down experiments we found that in dependency on c-Src and EGF-stimulation PKCepsilon may bind to the c-Src-specific phosphorylation site pY845-EGFR. Furthermore, we identified a single tyrosine residue, PKCepsilon-Y573, within a consensus binding sequence of the C-terminal SH2 domain of PLCgamma1 which is critical for both tyrosine phosphorylation of PKCepsilon and its association with PLCgamma1. Thus, in particular cells and independent of the kinase activity PKCepsilon may form a signalling module with EGFR and PLCgamma1. Thereby the tyrosine phosphorylation of PLCgamma1 via the EGFR may be facilitated. This is a novel function of PKCepsilon upstream of PLCgamma1 and a novel paradigm for the EGF-induced formation of multi-protein complexes.
Valkova
Christina
C
Institut für Biochemie und Biophysik, Biologisch-Pharmazeutische Fakultät, Friedrich-Schiller-Universität Jena, Philosophenweg 12, D-07743 Jena, Germany.
Maerz
Sabine
S
Imhof
Diana
D
Liebmann
Claus
C
D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002384:Catalysis / Q000187:drug effects; D002522:Chlorocebus aethiops; D016384:Consensus Sequence; D004789:Enzyme Activation / Q000187:drug effects; D004790:Enzyme Induction / Q000187:drug effects; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D066246:ErbB Receptors / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000378:metabolism; D051966:Phospholipase C gamma / Q000737:chemistry / Q000378:metabolism*; D019000:Phosphotyrosine / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D051744:Protein Kinase C-epsilon / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000378:metabolism; D034622:RNA Interference; D018909:src Homology Domains
D050505:Mutant Proteins; D019000:Phosphotyrosine; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D016392:Proto-Oncogene Proteins pp60(c-src); D051744:Protein Kinase C-epsilon; D051966:Phospholipase C gamma