title: Endothelin-1 activates mesangial cell ERK1/2 via EGF-receptor transactivation and caveolin-1 interaction.
abstract: Endothelin-1 (ET-1) stimulates glomerular mesangial cell proliferation and extracellular matrix protein transcription through an ERK1/2-dependent pathway. In this study, we determined whether ET-1 activation of glomerular mesangial cell ERK1/2 is mediated through EGF receptor (EGF-R) transactivation and whether intact caveolae are required. We showed that ET-1 stimulated tyrosine phosphorylation of the EGF-R in primary cultured, growth-arrested rat mesangial cells. In response to ET-1, ERK1/2 phosphorylation was increased by 27 +/- 1-fold and attenuated by AG-1478, a specific EGF-R inhibitor, to 9 +/- 1-fold. Moreover, filipin III and beta-cyclodextrin, two cholesterol-depleting drugs known to disrupt caveolae, significantly reduced ET-1-induced phosphorylation of ERK1/2. In addition, preincubation of mesangial cells with a myristoylated peptide that binds to the caveolin-1 scaffolding domain diminished ET-1 activation of ERK1/2. ET-1 caused interaction of caveolin-1 with phosphorylated ERK1/2 identified by coimmunoprecipitation. Activation of ERK1/2 and its interaction with caveolin-1 were reduced by AG-1478, beta-cyclodextrin, or inhibition of PKC. Phosphorylated ERK1/2 localized at focal adhesion complexes along with phospho-caveolin-1, suggesting specific sites of compartmentalization of these signaling molecules. Hence, ET-1 activates mesangial cell ERK1/2 predominantly through a pathway involving EGF-R transactivation, leading to a mechanism involving attachment to caveolin-1, presumably in caveolae.
authors.affiliation: Institute of Medical Science, Department of Medicine, University of Toronto, Toronto, Ontario, Canada M5S 1A8.
authors.forename: Hong
authors.initials: H
authors.lastname: Hua
authors.forename: Snezana
authors.initials: S
authors.lastname: Munk
authors.forename: Catharine I
authors.initials: CI
authors.lastname: Whiteside
mesh_terms: D000818:Animals; D051242:Caveolin 1; D022461:Caveolins / Q000502:physiology*; D002478:Cells, Cultured; D019332:Endothelin-1 / Q000502:physiology*; D004789:Enzyme Activation / Q000502:physiology; D066246:ErbB Receptors / Q000235:genetics*; D005455:Fluorescent Antibody Technique; D005920:Glomerular Mesangium / Q000166:cytology / Q000201:enzymology*; D007158:Immunologic Techniques; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D015533:Transcriptional Activation / Q000502:physiology*
chemical_list: C495537:Cav1 protein, rat; D051242:Caveolin 1; D022461:Caveolins; D019332:Endothelin-1; D066246:ErbB Receptors; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases