Open Accessmicro RNA let‐7g suppresses PDGF ‐induced conversion of vascular smooth muscle cell into the synthetic phenotype
Author(s) -
Wang TzuMing,
Chen KuChung,
Hsu PoYuan,
Lin HsiuFen,
Wang YungSong,
Chen ChienYuan,
Liao YiChu,
Juo SuhHang H.
Publication year - 2017
Publication title -
journal of cellular and molecular medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.44
H-Index - 130
eISSN - 1582-4934
pISSN - 1582-1838
DOI - 10.1111/jcmm.13269
Subject(s) - calponin , pdgfb , myocardin , platelet derived growth factor receptor , vascular smooth muscle , serum response factor , mapk/erk pathway , microbiology and biotechnology , biology , reporter gene , kinase , transfection , growth factor , gene expression , actin , gene , biochemistry , endocrinology , receptor , smooth muscle
Platelet‐derived growth factor ( PDGF ) can promote vascular smooth muscle cells ( VSMC s) to switch from the quiescent contractile phenotype to synthetic phenotype, which contributes to atherosclerosis. We aimed to investigate the role of micro RNA 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 ( MEKK 1)/extracellular signal‐regulated kinase ( ERK )/Krüppel‐like factor‐4 ( KLF 4) 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 / MEKK 1/ ERK / KLF 4 signalling pathway, PDGF ‐ BB can inhibit α‐ SMA and calponin. The PDGFB and MEKK 1 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 MEKK 1 levels. Moreover, we showed that let‐7g decreased phosphorylated‐ ERK 1/2 while had no effect on total ERK 1/2. KLF 4 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 KLF 4 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 / MEKK 1/ ERK / KLF 4 signalling to maintain VSMC in the contractile status, which further reduce VSMC atherosclerotic change.