Caveolin-1-deficient aortic smooth muscle cells show cell autonomous abnormalities in proliferation, migration, and endothelin-based signal transduction.
We previously showed that ablation of caveolin-1 (Cav-1) gene expression in mice promotes neointimal hyperplasia in vivo, a phenomenon normally characterized by smooth muscle cell (SMC) migration and proliferation. Whether these defects are cell autonomous, i.e., due to loss of Cav-1 within SMCs or loss of Cav-1 expression in other adjacent cell types in vivo, remains unknown. Cav-1 has been shown to associate with receptors for many vasoactive factors on the SMC surface. Therefore, Cav-1 might be an important regulator of SMC proliferation, migration, and signal transduction. To mechanistically dissect the role of Cav-1 in SMC signaling, we isolated SMCs from the aortas (AoSMCs) of Cav-1-deficient (Cav-1(-/-)) mice and characterized these cells with respect to their proliferation, migration, and Ca(2+) response to an important vasoactive factor, endothelin-1 (ET-1). 5-Bromo-2'-deoxyuridine incorporation and a wound-healing assay showed an increase in proliferation and migration rates in Cav-1(-/-) compared with wild-type (Cav-1(+/+)) AoSMCs. Cav-1(-/-) AoSMCs demonstrated upregulation of phosphorylated ERK1/2, cyclin D1, and proliferating cell nuclear antigen and reduced expression of the cyclin-dependent kinase inhibitor p27(Kip1). The Ca(2+) response was examined in the presence of ET-1 and assessed by confocal microscopy with the Ca(2+)-sensitive fluorescent probe fluo 3. When treated with ET-1, Cav-1(-/-) AoSMCs exhibited a faster and larger increase in free intracellular Ca(2+) than Cav-1(+/+) cells. The ET-1-induced response in Cav-1(-/-) cells was mediated by the ET(B) receptor, as shown using the ET(B) receptor antagonist BQ-788 and the ET(A) receptor antagonist BQ-123. In Cav-1(-/-) cells, ET(A) receptor expression was reduced and ET(B) receptor expression was upregulated. Therefore, Cav-1 ablation increased the ET-1-induced Ca(2+) response in SMCs by altering the type and expression level of the ET receptor (i.e., receptor isoform switching). These data suggest a novel regulatory role for Cav-1 in SMCs with respect to their proliferation, migration, and Ca(2+)-mediated signaling.
Hassan
Ghada S
GS
Department of Molecular Pharmacology and Medicine, Albert Einstein College of Medicine, Bronx, NY, USA.
Williams
Terence M
TM
Frank
Philippe G
PG
Lisanti
Michael P
MP
D000818:Animals; D000963:Antimetabolites / Q000494:pharmacology; D001011:Aorta / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D001973:Bromodeoxyuridine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D051242:Caveolin 1 / Q000172:deficiency* / Q000235:genetics; D018797:Cell Cycle Proteins / Q000502:physiology; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology; D049109:Cell Proliferation / Q000187:drug effects; D002469:Cell Separation; D002478:Cells, Cultured; D019332:Endothelin-1 / Q000502:physiology; D016232:Endothelins / Q000502:physiology*; D004789:Enzyme Activation / Q000502:physiology; D005455:Fluorescent Antibody Technique; D015151:Immunoblotting; D066298:In Vitro Techniques; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018613:Microscopy, Confocal; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D014945:Wound Healing / Q000187:drug effects
D000963:Antimetabolites; D051242:Caveolin 1; D018797:Cell Cycle Proteins; D019332:Endothelin-1; D016232:Endothelins; D019950:Mitogen-Activated Protein Kinase 1; D001973:Bromodeoxyuridine; D002118:Calcium