on April 6, 2006
Published online before print April 6, 2006, doi: 10.1161/01.ATV.0000220377.51354.30
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Submitted on February 13, 2006
Accepted on March 23, 2006
N-Terminal Proteolysis of the Endothelin B Receptor Abolishes Its Ability to Induce EGF Receptor Transactivation and Contractile Protein Expression in Vascular Smooth Muscle Cells
Evelina Grantcharova ;
From the Institut für Pharmakologie (E.G., W.R., A.O.), Charité Campus Benjamin Franklin, Berlin, Germany; Forschungsinstitut für Molekulare Pharmakologie (E.G., J.E., M.B., W.R., A.O.), Campus Berlin-Buch, Berlin, Germany; Abteilung für Klinische Pharmakologie (H.P.R.), Ruhr-Universität Bochum, Germany; and Roche-Diagnostics GmbH (H.-W.K.), Pharma-Research Penzberg, Germany.
* To whom correspondence should be addressed. E-mail: alexander.oksche{at}charite.de.
Objective--The extracellular N terminus of the endothelin B (ETB) receptor is cleaved by a metalloprotease in an agonist-dependent manner, but the physiological role of this N-terminal proteolysis is not known. In this study, we aimed to determine the functional role of the ETB receptor and of its N-terminal cleavage in vascular smooth muscle cells (VSMCs).
Methods and Results--VSMCs expressing either the full-length ETB receptor or an N-terminally truncated ETB receptor (corresponding to the N-terminally cleaved receptor) were analyzed for ligand-induced mitogen-activated protein kinase activation and expression of contractile proteins. In VSMCs expressing the full-length ETB receptor, IRL1620 (an ETB-selective agonist) induced a biphasic extracellular signal-regulated kinase 1/2 (ERK1/2) activation and increased expression of contractile proteins (smooth muscle myosin-1 [SM-1]/SM-2, SM22
, and -actin). Interestingly, the second phase of ERK1/2 activation required metalloprotease activity, EGF receptor transactivation, and predominantly activation of Gi proteins. In contrast, in VSMCs expressing N-terminally truncated ETB receptors, IRL1620 did not elicit EGF transactivation and failed to increase contractile protein expression.
Conclusions--This study is the first to show that stimulation of full-length ETB receptors promotes expression of contractile proteins and may thus participate in the differentiation of VSMCs.
Key words: transactivation • EGF receptor • ERK1/2 • differentiation