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.
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).


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, SM22alpha, and alpha-actin). Interestingly, the second phase of ERK1/2 activation required metalloprotease activity, epidermal growth factor (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.
Grantcharova
Evelina
E
Institut für Pharmakologie, Charité Campus Benjamin Franklin, Berlin, Germany.
Reusch
H Peter
HP
Grossmann
Solveig
S
Eichhorst
Jenny
J
Krell
Hans-Willi
HW
Beyermann
Michael
M
Rosenthal
Walter
W
Oksche
Alexander
A
D000818:Animals; D002478:Cells, Cultured; D003285:Contractile Proteins / Q000378:metabolism*; D016232:Endothelins / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D066246:ErbB Receptors / Q000235:genetics*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000502:physiology; D049452:Green Fluorescent Proteins / Q000235:genetics; D006801:Humans; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D009154:Mutation; D032389:Myocytes, Smooth Muscle / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism / Q000494:pharmacology; D010447:Peptide Hydrolases / Q000378:metabolism*; D051381:Rats; D044023:Receptor, Endothelin B / Q000819:agonists / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000187:drug effects / Q000378:metabolism / Q000494:pharmacology; D015533:Transcriptional Activation
D003285:Contractile Proteins; D016232:Endothelins; D010446:Peptide Fragments; D044023:Receptor, Endothelin B; D011993:Recombinant Fusion Proteins; C074308:sovateltide; D049452:Green Fluorescent Proteins; D066246:ErbB Receptors; D048049:Extracellular Signal-Regulated MAP Kinases; D010447:Peptide Hydrolases; D019206:GTP-Binding Protein alpha Subunits, Gi-Go