Expression and function of COOH-terminal myosin heavy chain isoforms in mouse smooth muscle
Expression and function of COOH-terminal myosin heavy chain isoforms in mouse smooth muscle
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DOI：
10.1152/ajpcell.00567.2006
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发表时间：
2007-07-01
影响因子：
5.5
通讯作者：
Paul, Richard J.
中科院分区：
文献类型：
--
作者：
Martin, Anne F.;Bhatti, Sunita;Paul, Richard J.
平滑肌肌球蛋白马达的亚型SM 1和SM 2在羧基末端尾区的长度不同。它们的比例随着发育、激素状态和疾病而变化，但它们的功能尚不清楚。我们开发了携带肌球蛋白重链（MyHC）转基因SM 1、cMyc标记的SM 1、SM 2和V5标记的SM 2的小鼠，并且所有转基因对应于SMa NH 2末端同种型。通过平滑肌α-肌动蛋白启动子将转基因表达靶向平滑肌。免疫印迹分析显示，cMyc标记的SM 1和V5标记的SM 2 MyHC蛋白在主动脉和膀胱中大量表达，并且转基因mRNA在携带未标记的SM 1或SM 2转基因的小鼠中表达。尽管标记的MyHCs的蛋白质表达显著，但我们发现SM 1：SM 2蛋白质比率仅发生微小变化。在携带未标记的SM 1或SM 2转基因的小鼠中观察到功能表型的显著变化。SM 1转基因小鼠的主动脉和膀胱中的力增加（72 +/-14%，92 +/- 11%），而SM 2转基因小鼠中的力降低至57 +/- 1%和80 +/- 3%。在快速缩短步长后，SM 1转基因膀胱具有更快（1.8 +/- 0.3 s）和SM 2更慢（7.1 +/- 0.5 s）的力重建速率。我们假设，SM 1：SM 2比例的微小变化可能会被放大，如果它们与粗丝组装的变化相关，并成为收缩性改变的基础。这些数据提供的证据表明，在体内的平滑肌肌球蛋白的COOH-末端亚型的功能，并表明，SM 1：SM 2的比例在平滑肌组织中受到严格的监管。
Isoforms of the smooth muscle myosin motor, SM1 and SM2, differ in length at the carboxy terminal tail region. Their proportion changes with development, hormonal status and disease, but their function is unknown. We developed mice carrying the myosin heavy chain (MyHC) transgenes SM1, cMyc-tagged SM1, SM2, and V5-tagged SM2, and all transgenes corresponded to the SMa NH2-terminal isoform. Transgene expression was targeted to smooth muscle by the smooth muscle alpha-actin promoter. Immunoblot analysis showed substantial expression of the cMyc-tagged SM1 and V5-tagged SM2 MyHC protein in aorta and bladder and transgene mRNA was expressed in mice carrying unlabeled SM1 or SM2 transgenes. Despite significant protein expression of tagged MyHCs we found only small changes in the SM1: SM2 protein ratio. Significant changes in functional phenotype were observed in mice carrying unlabeled SM1 or SM2 transgenes. Force in aorta and bladder was increased (72 +/- 14%, 92 +/- 11%) in SM1 and decreased to 57 +/- 1% and 80 +/- 3% in SM2 transgenic mice. SM1 transgenic bladders had faster (1.8 +/- 0.3 s) and SM2 slower (7.1 +/- 0.5 s) rates of force redevelopment following a rapid step shortening. We hypothesize that small changes in the SM1:SM2 ratio could be amplified if they are associated with changes in thick filament assembly and underlie the altered contractility. These data provide evidence indicating an in vivo function for the COOH-terminal isoforms of smooth muscle myosin and suggest that the SM1:SM2 ratio is tightly regulated in smooth muscle tissues.