Induction of MicroRNA-221 by Platelet-derived Growth Factor Signaling Is Critical for Modulation of Vascular Smooth Muscle Phenotype*
- ‡Department of Biochemistry, Tufts University School of Medicine, and the §Molecular Cardiology Research Institute, Tufts Medical Center, Boston, Massachusetts 02111
- 2 To whom correspondence should be addressed: Molecular Cardiology Research Institute, Tufts Medical Center, 800 Washington St., Box 8486, Boston, MA 02111. Tel.: 617-636-0614; Fax: 617-636-5649; E-mail: akiko.hata{at}tufts.edu.
Abstract
The platelet-derived growth factor (PDGF) signaling pathway is a critical regulator of animal development and homeostasis. Activation of the PDGF pathway leads to neointimal proliferative responses to artery injury; it promotes a switch of vascular smooth muscle cells (vSMC) to a less contractile phenotype by inhibiting the SMC-specific gene expression and increasing the rate of proliferation and migration. The molecular mechanism for these pleiotropic effects of PDGFs has not been fully described. Here, we identify the microRNA-221 (miR-221), a small noncoding RNA, as a modulator of the phenotypic change of vSMCs in response to PDGF signaling. We demonstrate that miR-221 is transcriptionally induced upon PDGF treatment in primary vSMCs, leading to down-regulation of the targets c-Kit and p27Kip1. Down-regulation of p27Kip1 by miR-221 is critical for PDGF-mediated induction of cell proliferation. Additionally, decreased c-Kit causes inhibition of SMC-specific contractile gene transcription by reducing the expression of Myocardin (Myocd), a potent SMC-specific nuclear coactivator. Our study demonstrates that PDGF signaling, by modulating the expression of miR-221, regulates two critical determinants of the vSMC phenotype; they are SMC gene expression and cell proliferation.
Footnotes
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↵3 The abbreviations used are: SMC, smooth muscle cell(s); vSMC, vascular SMC; PDGF, platelet-derived growth factor; PDGFR, PDGF receptor; UTR, untranslated region; mi-, micro-; CNN, smooth muscle calponin; IPAH, idiopathic pulmonary artery hypertension; Myocd, myocardin; PASMC, pulmonary artery smooth muscle cells; siRNA, small interference RNA; DAPI, 4′-6-Diamidino-2-phenylindole; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; SCF, stem cell factor; qRT, quantitative real-time; GFP, green fluorescent protein; FITC, fluorescein isothiocyanate; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; PCNA, proliferating cell nuclear antigen; BMP, bone morphogenetic protein; SMA, α-smooth muscle actin.
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↵* This work was supported, in whole or in part, by National Institutes of Health Grants HL082854 (to A. Hata) and HL086572 (to G. L.) (NIHLB). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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The on-line version of this article (available at http://www.jbc.org) contains supplemental Figs. S1 and S2.
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↵1 These authors contributed equally to this work.
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- Received November 19, 2008.
- Revision received December 15, 2008.
- The American Society for Biochemistry and Molecular Biology, Inc.
