Epidermal growth factor-stimulated tyrosine phosphorylation of caveolin-1. Enhanced caveolin-1 tyrosine phosphorylation following aberrant epidermal growth factor receptor status.
Caveolin-1 is the major coat protein of caveolae and has been reported to interact with various intracellular signaling molecules including the epidermal growth factor (EGF) receptor. To investigate the involvement of caveolin-1 in EGF receptor action, we used mouse B82L fibroblasts transfected with (a) wild type EGF receptor, (b) a C-terminally truncated EGF receptor at residue 1022, (c) a C-terminally truncated EGF receptor at residue 973, or (d) a kinase-inactive EGF receptor (K721M). Following EGF treatment, there was a distinct electrophoretic mobility shift of the caveolin-1 present in cells expressing the truncated forms of the EGF receptor, but this shift was not detectable in cells bearing either normal levels of the wild type EGF receptor or a kinase-inactive receptor. This mobility shift was also not observed following the addition of other cell stimuli, such as platelet-derived growth factor, insulin, basic fibroblast growth factor, or phorbol 12-myristate 13-acetate. Analysis of caveolin-1 immunoprecipitates from EGF-stimulated or nonstimulated cells demonstrated that the EGF-induced mobility shift of caveolin-1 was associated with its tyrosine phosphorylation in cells expressing truncated EGF receptors. Maximal caveolin-1 phosphorylation was achieved within 5 min after exposure to 10 nM EGF and remained elevated for at least 2 h. Additionally, several distinct phosphotyrosine-containing proteins (60, 45, 29, 24, and 20 kDa) were co-immunoprecipitated with caveolin-1 in an EGF-dependent manner. Furthermore, the Src family kinase inhibitor, PP1, does not affect autophosphorylation of the receptor, but it does inhibit the EGF-induced mobility shift and phosphorylation of caveolin-1. Conversely, the MEK inhibitors PD98059 and UO126 could attenuate EGF-induced mitogen-activated protein kinase activation, they do not affect the EGF-induced mobility shift of caveolin-1. Because truncation and overexpression of the EGF receptor have been linked to cell transformation, these results provide the first evidence that the tyrosine phosphorylation of caveolin-1 occurs via an EGF-sensitive signaling pathway that can be potentiated by an aberrant activity or expression of various forms of the EGF receptor.
Kim
Y N
YN
Department of Biomolecular Chemistry and Endocrinology and Reproductive Physiology Program, University of Wisconsin, Madison, Wisconsin 53706-1532, USA.
Wiepz
G J
GJ
Guadarrama
A G
AG
Bertics
P J
PJ
D000818:Animals; D051242:Caveolin 1; D022461:Caveolins; D002471:Cell Transformation, Neoplastic; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism*; D005419:Flavonoids / Q000494:pharmacology; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors; D009154:Mutation; D010766:Phosphorylation; D020033:Protein Isoforms / Q000378:metabolism; D011720:Pyrazoles / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction; D014443:Tyrosine; D019061:src-Family Kinases / Q000037:antagonists & inhibitors
C108123:4-amino-5-(4-methylphenyl)-7-(tert-butyl)pyrazolo(3,4-d)pyrimidine; C495541:Cav1 protein, mouse; D051242:Caveolin 1; D022461:Caveolins; D005419:Flavonoids; D008565:Membrane Proteins; D020033:Protein Isoforms; D011720:Pyrazoles; D011743:Pyrimidines; D011994:Recombinant Proteins; D014443:Tyrosine; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D019061:src-Family Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one