The lysine methyltransferase SMYD2 facilitates neointimal hyperplasia by regulating the HDAC3-SRF axis

Coronary restenosis is an important cause of poor long-term prognosis in patients with coronary heart disease.Here,we show that lysine methyltransferase SMYD2 expression in the nucleus is significantly elevated in serum-and PDGF-BB-induced vascular smooth muscle cells(VSMCs),and in tissues of carotid artery injury-induced neointimal hyperplasia.Smyd2 overexpression in VSMCs(Smyd2-vTg)facilitates,but treatment with its specific inhibitor LLY-507 or SMYD2 knockdown significantly inhibits VSMC phenotypic switching and carotid artery injury-induced neointima formation in mice.Transcriptome sequencing revealed that SMYD2 knockdown represses the expression of serum response factor(SRF)target genes and that SRF overexpression largely reverses the inhibitory effect of SMYD2 knockdown on VSMC proliferation.HDAC3 directly interacts with and deacetylates SRF,which enhances SRF transcriptional activity in VSMCs.Moreover,SMYD2 promotes HDAC3 expression via tri-methylation of H3K36 at its promoter.RGFP966,a specific inhibitor of HDAC3,not only counteracts the pro-proliferation effect of SMYD2 overexpression on VSMCs,but also inhibits carotid artery injury-induced neointima formation in mice.HDAC3 partially abolishes the inhibitory effect of SMYD2 knockdown on VSMC proliferation in a deacetylase activity-dependent manner.Our results reveal that the SMYD2-HDAC3-SRF axis constitutes a novel and critical epigenetic mechanism that regulates VSMC phenotypic switching and neointimal hyperplasia.

新型β-葡萄糖苷酶BglD2异源表达及水解虎杖苷能力

从海洋细菌Bacillus sp.D1中克隆、重组表达β-葡萄糖苷酶BglD2,研究其酶学性质,并对其水解虎杖苷制备白藜芦醇的能力进行分析。BglD2的最适催化温度和pH分别为45℃和6.5,在30℃和pH 6.5条件下的半衰期约为20 h。BglD2能够水解含β(1→3)、β(1→4)、β(1→6)等键型的多种底物。BglD2具有良好的糖促活特性,100 mmol/L葡萄糖和150 mmol/L木糖分别将酶活力提升2.0倍和2.3倍。BglD2具有较好的乙醇促活及耐受特性,30℃时,10%乙醇使酶活力提升1.2倍,25%乙醇存在时其仍保留60%的酶活力。BglD2具有水解虎杖苷制备白藜芦醇的能力,35℃条件下反应2 h水解率为86%。具有乙醇耐受及抗产物抑制等特性的β-葡萄糖苷酶BglD2在酶法水解虎杖苷制备白藜芦醇方面有应用潜力。