microRNA let‐7g suppresses PDGF‐induced conversion of vascular smooth muscle cell into the synthetic phenotype |
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| Authors: | Tzu‐Ming Wang Ku‐Chung Chen Po‐Yuan Hsu Hsiu‐Fen Lin Yung‐Song Wang Chien‐Yuan Chen Yi‐Chu Liao Suh‐Hang H. Juo |
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| Affiliation: | 1. Department of Medical Research, China Medical University Hospital, Taichung, Taiwan;2. Department of Biochemistry and Molecular Cell Biology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan;3. Department of Neurology, Kaohsiung Medical University, Kaohsiung, Taiwan;4. Department of Life Science, National Taiwan University, Taipei, Taiwan;5. Institute of Fisheries Science, National Taiwan University, Taipei, Taiwan;6. Graduate Institute of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan;7. Department of Neurology, National Yang‐Ming University School of Medicine, Taipei, Taiwan;8. Department of Neurology, Taipei Veterans General Hospital, Taipei, Taiwan;9. Graduate Institute of Biomedical Sciences, China Medical University, Taichung, Taiwan;10. Institute of New Drug Development, China Medical University, Taichung, Taiwan;11. Brain disease research center, China Medical University, Taichung, Taiwan |
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| Abstract: | Platelet‐derived growth factor (PDGF) can promote vascular smooth muscle cells (VSMCs) to switch from the quiescent contractile phenotype to synthetic phenotype, which contributes to atherosclerosis. We aimed to investigate the role of microRNA let‐7g in phenotypic switching. Bioinformatics prediction was used to find let‐7g target genes in the PDGF/mitogen‐activated protein kinase kinase kinase 1 (MEKK1)/extracellular signal‐regulated kinase (ERK)/Krüppel‐like factor‐4 (KLF4) signalling pathway that affects VSMC phenotypic switching. The luciferase reporter assay and let‐7g transfection were used to confirm let‐7g target genes. Two contractile proteins alpha‐smooth muscle actin (α‐SMA) and calponin were VSMC‐specific genes and were measured as the indicators for VSMC phenotype. Lentivirus carrying the let‐7g gene was injected to apolipoprotein E knockout (apoE?/?) mice to confirm let‐7g's effect on preventing atherosclerosis. Through the PDGF/MEKK1/ERK/KLF4 signalling pathway, PDGF‐BB can inhibit α‐SMA and calponin. The PDGFB and MEKK1 genes were predicted to harbour let‐7g binding sites, which were confirmed by our reporter assays. Transfection of let‐7g to VSMC also reduced PDGFB and MEKK1 levels. Moreover, we showed that let‐7g decreased phosphorylated‐ERK1/2 while had no effect on total ERK1/2. KLF4 can reduce VSMC‐specific gene expression by preventing myocardin–serum response factor (SRF) complex from associating with these gene promoters. The immunoprecipitation assay showed that let‐7g decreased the interaction between KLF4 and SRF. Further experiments demonstrated that let‐7g can increase α‐SMA and calponin levels to maintain VSMC in the contractile status. Injection of lentivirus carrying let‐7g gene increased let‐7g's levels in aorta and significantly decreased atherosclerotic plaques in the apoE?/? mice. We demonstrated that let‐7g reduces the PDGF/MEKK1/ERK/KLF4 signalling to maintain VSMC in the contractile status, which further reduce VSMC atherosclerotic change. |
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| Keywords: | microRNA let‐7g
PDGF
vascular smooth muscle cell α ‐SMA calponin atherosclerosis |
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