SM22α对血管平滑肌细胞骨架及收缩功能的影响

SM22α(smooth muscle 22 alpha,SM22α)是血管平滑肌细胞(vascular smooth muscle cells,VSMC)的标志蛋白,为了探讨该蛋白与VSMC表型和功能的关系,利用血清饥饿法诱导VSMC由合成型向收缩型转变,用RT—PCR对不同表型VSMC的SM22α表达活性进行检测,并通过转染反义SM22α表达载体,观察SM22α表达对VSMC细胞骨架和收缩功能的影响。结果显示,在VSMC由合成型逆转为收缩型的过程中,SM22α和平滑肌α-肌动蛋白(smooth muscle α—actin,SMα—actin)的表达分别被显诱导和轻度上调,与此同时,细胞骨架由稀疏的网格状变成均匀、致密的束状,VSMC重新获得收缩功能。用反义SM22α抑制该基因表达后,血清饥饿诱导的VSMC细胞骨架重构受阻,乙酰胆碱刺激引发的细胞收缩消失。结果提示,SM22α参与VSMC细胞骨架的构成及调节细胞的收缩功能,对维持VSMC处于收缩表型具有重要作用。     

PDGF-BB下调血管平滑肌标志物SM22α表达的机制

血管平滑肌细胞（vascular smooth muscle cell,VSMC）表型转化是血管重塑性疾病的细胞病理学基础,血小板源性生长因子（platelet-derived growth factor,PDGF）-BB抑制平滑肌分化标志基因表达、加速其降解,是VSMC表型转化的关键。该研究用PDGF-BB刺激VSMC诱导细胞发生表型转化,利用Western blot和免疫共沉淀等技术,检测PDGF-BB对早期分化相关基因平滑肌22 alpha（smooth muscle 22 alpha,SM22α）磷酸化与泛素化的影响。实验结果显示,PDGF-BB促进VSMC增殖;上调增殖相关蛋白PCNA的表达,下调分化相关蛋白SM22α与SMα-actin的表达;诱导SM22α发生磷酸化和泛素化,而且,该过程与SM22α水平下调具有时相相关性;抑制剂阻断分析证实,ERK和PKC参与介导了PDGF-BB诱导的SM22α磷酸化。以上结果提示,在VSMCs表型转化中,PDGF-BB可能是通过激活ERK-PKC信号通路,促进SM22α的磷酸化和泛素依赖的蛋白质降解。     

SM22α在血管平滑肌细胞中的作用

平滑肌22α(SM22α)是平滑肌细胞(VSMC)骨架相关蛋白,通过与肌动蛋白的作用参与VSMC骨架重构,是近年发现的一种VSMC分化标志物,其表达具有平滑肌组织特异性和细胞表型特异性.血管平滑肌细胞(VSMC)表型转化是动脉粥样硬化、高血压等血管重塑性疾病的共同病理生理过程.VSMC表型转化过程中平滑肌特异基因的表达变化和细胞骨架的重构是当前研究的热点问题之一.本文就SM22α的结构特征及其在VSMC中的作用机制进行综述.     

SM22α在细胞骨架组构及血管重塑中的作用

血管平滑肌细胞（VSMC）表型转化是动脉粥样硬化、高血压和血管成形术后再狭窄等血管重塑性疾病的共同病理生理过程。VSMC表型转化过程中平滑肌特异基因的表达变化和细胞骨架的组构是当前研究的热点问题之一。平滑肌22α（SM22α）是近年发现的一种VSMC分化标志物,其表达具有平滑肌组织特异性和细胞表型特异性,该蛋白作为一种肌动蛋白细胞骨架相关蛋白参与VSMC骨架组构和收缩调节。本文就SM22α的结构特征及其在VSMC骨架组构和血管重塑中的作用机制进行综述。     

平滑肌22α蛋白在血管稳态和血管重构中的作用

有关血管稳态和重构的分子机制一直是近年来的研究热点,也被视为治疗血管损伤性疾病的突破点.大量研究证实,血管损伤修复及病理性重构过程与血管平滑肌细胞(vascular smooth muscle cells,VSMCs)的表型转化、异常增殖与迁移、细胞衰老关系密切.平滑肌22α(smooth muscle 22α,SM2...     

细胞代数和密度影响血管平滑肌细胞表型重塑和收缩反应性的机制

探讨细胞代数和密度对血管平滑肌细胞(vascular smooth muscle cell,VSMC)表型重塑能力的影响及机制,观察血清饥饿诱导的不同代数和密度的VSMC骨架的组构特征及收缩反应性,检测细胞骨架中收缩蛋白的含量和比例变化。结果发现,低代数(3代)、高密度的VSMC经血清饥饿诱导后易于形成束状、极性排列的应力纤维,乙酰胆碱(Ach)刺激可产生明显的收缩反应。Western印迹显示,3代高密度VSMC中,平滑肌22α(SM22α)在F-肌动蛋白中的组成比例及其在F-/G-肌动蛋白的含量之比明显高于8代细胞。结果提示,SM22α在F-肌动蛋白中的分布比例可能决定了应力纤维的排布方式,是细胞获得收缩性的主要调节因素,在VSMC表型重塑过程中具有重要意义。     

Apelin-13促进血管平滑肌细胞增殖、迁移和血管新生内膜增生

研究apelin-13对血管平滑肌细胞（vascular smooth muscle cell, VSMC）增殖和迁移的影响及其作用机制.用免疫印迹分析检测apelin-13对VSMC增殖、迁移以及分化相关基因表达的影响,结果表明,apelin-13能以时间和浓度依赖的方式诱导VSMC增殖和迁移相关基因cyclin D1和MMP-2表达,促进细胞增殖和迁移;同时使VSMC分化标志基因SM22α和SM α-actin表达水平降低.而且,用鬼笔环肽对细胞骨架进行染色的结果显示,apelin-13可以促进VSMC从收缩表型向增殖表型转化.体内实验也表明,敲低apelin可抑制球囊损伤诱导的新生内膜形成,提示apelin-13在体内具有促进血管新生内膜形成的作用.总之,本文结果表明,apelin 13通过调节VSMC增殖、迁移以及分化基因表达,进而促进其从分化型向增殖型转化,并向内膜下迁移和增殖.     

SM22α参与血清饥饿诱导的血管平滑肌细胞微丝重塑

血清饥饿可诱导体外培养的血管平滑肌细胞(vascularsmoothmusclecells,VSMC)由合成型转变为收缩型,微丝重塑是该过程的一个重要事件。平滑肌22α(smoothmuscle22alpha,SM22α)是VSMC的标志蛋白,为了证实SM22α是否参与调节VSMC的微丝重塑过程,采用反义技术,封闭SM22α表达,利用间接免疫荧光染色、透射电镜观察SM22α表达对VSMC微丝重塑的影响,利用细胞平面迁移实验观察SM22α表达对VSMC运动功能的影响。实验结果显示,在血清饥饿培养的VSMC中,伴随着SM22α和SMα肌动蛋白表达上调,微丝数量明显增多,呈极性束状分布。用反义SM22α抑制SM22α表达后,血清饥饿诱导的VSMC微丝重塑受阻,微丝纤细,排列紊乱,且细胞迁移活性下降。结果提示,在VSMC微丝组装过程中,SM22α可能起一种捆绑蛋白作用。     

细胞骨架相关蛋白SM22α与肿瘤

平滑肌22α(smooth muscle 22 alpha,SM22α)蛋白是一种细胞骨架相关蛋白,其在种属间的高度同源性和进化上的高度保守性提示了其重要的生物学意义.最新研究发现,SM22α在多种肿瘤组织中表达异常,该蛋白除可通过与肌动蛋白相互作用参与细胞骨架重构外,还可作为信号分子参与细胞生长,细胞外基质降解和血管生成.其作为一种新型抑癌基因,在肿瘤发生,发展中的作用日益成为人们关注的焦点.本文就SM22α的结构特征、表达特点及其与肿瘤的关系进行综述.     

SM22α对血管平滑肌细胞肌动蛋白聚合和交联的调节

目的:探讨平滑肌22alpha(SM22α)调节血管平滑肌细胞(VSMC)骨架重构的分子机制。方法:血清饥饿法诱导VSMC由合成型转化成收缩型,转染pEGFP-SM22α表达质粒后观察SM22α在细胞中的分布及其与肌动蛋白纤丝(F-actin)的定位关系;应用反义技术封闭内源性SM22α表达,蛋白分步提取和Western blot分析检测敲减SM22α基因表达对肌动蛋白单体G-actin聚合的影响;F-actin体外交联实验观察SM22α对F-actin交联成束的影响。结果:SM22α在细胞中的分布与F-actin相一致;抑制内源性SM22α表达后,细胞中的SMα-actin主要以可溶性单体G-actin形式存在;F-actin体外交联实验结果表明,GST-SM22α蛋白纯品可促进F-actin交联形成粗大、束状的应力纤维,而敲减内源性SM22α的细胞裂解液促进F-actin交联的活性明显降低。结论:SM22α是参与VSMC细胞骨架重构的调节蛋白,不仅可促进G-actin聚合形成F-actin,而且还可加速F-actin交联成束,在VSMC骨架重构过程中起着十分重要的作用。     

Angiogenic factor AGGF1 blocks neointimal formation after vascular injury via interaction with integrin α7 on vascular smooth muscle cells

Angiogenic factor AGGF1 (AngioGenic factor with G-patch and FHA (Forkhead-Associated) domain 1) blocks neointimal formation (formation of a new or thickened layer of arterial intima) after vascular injury by regulating phenotypic switching of vascular smooth muscle cells (VSMCs). However, the AGGF1 receptor on VSMCs and the underlying molecular mechanisms of its action are unknown. In this study, we used functional analysis of serial AGGF1 deletions to reveal the critical AGGF1 domain involved in VSMC phenotypic switching. This domain was required for VSMC phenotypic switching, proliferation, cell cycle regulation, and migration, as well as the regulation of cell cycle inhibitors cyclin D, p27, and p21. This domain also contains an RDDAPAS motif via which AGGF1 interacts with integrin α7 (ITGA7), but not α8. In addition, we show that AGGF1 enhanced the expression of contractile markers MYH11, α-SMA, and SM22 and inhibited MEK1/2, ERK1/2, and ELK phosphorylation in VSMCs, and that these effects were inhibited by knockdown of ITGA7, but not by knockdown of ITGA8. In vivo, deletion of the VSMC phenotypic switching domain in mice with vascular injury inhibited the functions of AGGF1 in upregulating α-SMA and SM22, inhibiting MEK1/2, ERK1/2, and ELK phosphorylation, in VSMC proliferation, and in blocking neointimal formation. Finally, we show the inhibitory effect of AGGF1 on neointimal formation was blocked by lentivirus-delivered shRNA targeting ITGA7. Our data demonstrate that AGGF1 interacts with its receptor integrin α7 on VSMCs, and this interaction is required for AGGF1 signaling in VSMCs and for attenuation of neointimal formation after vascular injury.     

血清饥饿可诱导人血管平滑肌细胞再分化

体外培养的分化型血管平滑肌细胞 (vascularsmoothmusclecells ,VSMC)以特异性标志基因表达、长梭形外观及对兴奋剂刺激产生收缩反应为其表型特征 .以血清饥饿法培养处于超汇合 (overconfluence)状态的人VSMC ,观察其分化型标志基因表达活性及其与细胞形态特征和收缩反应性之间的关系 ,探讨细胞生存环境对VSMC基因表达及表型的影响 .研究显示 ,生长至超汇合的VSMC由含血清培养转为血清饥饿后 ,收缩蛋白如SMα肌动蛋白 (SMα actin)、SM2 2α、h1 calponin、肌球蛋白重链 (MHC)SM1和SM2亚型的表达活性明显上调 ,证实血清饥饿诱导的收缩蛋白基因表达和血清应答因子 (serumresponsefactor ,SRF)与CArG顺式元件结合活性的增强有关 .同时 ,血清饥饿还可激活参与VSMC分化调节的转录调控因子SmLIM、Gax和分化相关蛋白HRG 1基因的转录 .随着血清饥饿培养时间的延长 ,VSMC逐渐形成多层、束状、成极性排列的形式 ,对兴奋剂刺激产生的收缩反应明显增强 .结果表明 ,超汇合状态的去分化型VSMC脱离血清刺激后 ,可以再分化成熟并重新获得收缩能力     

TGF-beta superfamily members do not promote smooth muscle-specific alternative splicing, a late marker of vascular smooth muscle cell differentiation

Smooth muscle (SM) specific alternate splicing of a number of genes is a late marker of the differentiated vascular smooth muscle cell (VSMC) phenotype and is one of the first differentiation characteristics to be lost during de-differentiation and in disease. An understanding of how this aspect of VSMC phenotype is regulated may provide insights into the earliest events of the atherosclerotic process. TGF-beta1 is a potent regulator of VSMC differentiation and can induce expression of SM-specific contractile proteins in both pluripotent stem cells and de-differentiated VSMCs. The purpose of this study was to test the hypothesis that members of the TGFbeta-superfamily can also effect SM-specific alternative splicing. Firstly, we established that SM-specific splicing of alpha-tropomyosin, vinculin and SM-myosin heavy chain (MHC) increases during rat fetal/neonatal development and is decreased in VSMCs following balloon-induced carotid injury in the rat. Treatment of cultured rat VSMCs with TGFbeta-superfamily members resulted in a significant reduction in the ratio of SM to non-muscle (NM) alpha-tropomyosin, but did not effect SM-specific alternative splicing of vinculin or SM-MHC. Treatment of pluripotent C3H10T1/2 cells with TGF-beta1, which increased SM differentiation marker expression, did not increase SM-specific alpha-tropomyosin splicing. Taken together, these results demonstrate differential regulation of SM-specific alternative splicing and indicate that although TGF-beta1 promotes VSMC differentiation marker expression, TGF-beta1 cannot act as the sole trigger of VSMC differentiation.     

Resident phenotypically modulated vascular smooth muscle cells in healthy human arteries

Vascular interstitial cells (VICs) are non‐contractile cells with filopodia previously described in healthy blood vessels of rodents and their function remains unknown. The objective of this study was to identify VICs in human arteries and to ascertain their role. VICs were identified in the wall of human gastro‐omental arteries using transmission electron microscopy. Isolated VICs showed ability to form new and elongate existing filopodia and actively change body shape. Most importantly sprouting VICs were also observed in cell dispersal. RT‐PCR performed on separately collected contractile vascular smooth muscle cells (VSMCs) and VICs showed that both cell types expressed the gene for smooth muscle myosin heavy chain (SM‐MHC). Immunofluorescent labelling showed that both VSMCs and VICs had similar fluorescence for SM‐MHC and αSM‐actin, VICs, however, had significantly lower fluorescence for smoothelin, myosin light chain kinase, h‐calponin and SM22α. It was also found that VICs do not have cytoskeleton as rigid as in contractile VSMCs. VICs express number of VSMC‐specific proteins and display features of phenotypically modulated VSMCs with increased migratory abilities. VICs, therefore represent resident phenotypically modulated VSMCs that are present in human arteries under normal physiological conditions.     

Aldosterone enhances high phosphate–induced vascular calcification through inhibition of AMPK‐mediated autophagy

It remains unclear whether the necessity of calcified mellitus induced by high inorganic phosphate (Pi) is required and the roles of autophagy plays in aldosterone (Aldo)‐enhanced vascular calcification (VC) and vascular smooth muscle cell (VSMC) osteogenic differentiation. In the present study, we found that Aldo enhanced VC both in vivo and in vitro only in the presence of high Pi, alongside with increased expression of VSMC osteogenic proteins (BMP2, Runx2 and OCN) and decreased expression of VSMC contractile proteins (α‐SMA, SM22α and smoothelin). However, these effects were blocked by mineralocorticoid receptor inhibitor, spironolactone. In addition, the stimulatory effects of Aldo on VSMC calcification were further accelerated by the autophagy inhibitor, 3‐MA, and were counteracted by the autophagy inducer, rapamycin. Moreover, inhibiting adenosine monophosphate‐activated protein kinase (AMPK) by Compound C attenuated Aldo/MR‐enhanced VC. These results suggested that Aldo facilitates high Pi‐induced VSMC osteogenic phenotypic switch and calcification through MR‐mediated signalling pathways that involve AMPK‐dependent autophagy, which provided new insights into Aldo excess‐associated VC in various settings.