Kemp T J, Sadusky T J, Simon M, Brown R, Eastwood M, Sassoon D A, Coulton G R
Molecular Pathology, Imperial College of Science, Technology, and Medicine, London, SW7 2AZ, United Kingdom.
Genomics. 2001 Mar 15;72(3):260-71. doi: 10.1006/geno.2000.6461.
Skeletal muscle is able to respond to a range of stimuli, including stretch and increased load, by increasing in diameter and length in the absence of myofiber division. This type of cellular growth (hypertrophy) is a highly complex process involving division of muscle precursor cells (myoblasts) and their fusion to existing muscle fibers as well as increased protein synthesis and decreased protein degradation. Underlying the alterations in protein levels are increases in a range of specific mRNAs including those coding for structural proteins and proteins that regulate the hypertrophic process. Seven days of passive stretch in vivo of tibialis anterior (TA) muscle has been shown to elicit muscle hypertrophy. We have identified a cDNA corresponding to an mRNA that exhibits increased expression in response to 7 days of passive stretch imposed on TA muscles in vivo. This 944-bp novel murine transcript is expressed primarily in cardiac and skeletal muscle and to a lesser extent in brain. Translation of the transcript revealed an open reading frame of 85 amino acids encoding a nuclear localization signal and two overlapping casein kinase II phosphorylation sites. This gene has been called "small muscle protein (X chromosome)" (Smpx; HGMW-approved human gene symbol SMPX) and we hypothesize that it plays a role in skeletal muscle hypertrophy.
骨骼肌能够通过在无肌纤维分裂的情况下增加直径和长度，对一系列刺激做出反应，包括拉伸和负荷增加。这种类型的细胞生长（肥大）是一个高度复杂的过程，涉及肌肉前体细胞（成肌细胞）的分裂及其与现有肌纤维的融合，以及蛋白质合成增加和蛋白质降解减少。蛋白质水平变化的基础是一系列特定mRNA的增加，包括那些编码结构蛋白和调节肥大过程的蛋白质的mRNA。体内对胫骨前肌（TA）进行七天的被动拉伸已被证明可引起肌肉肥大。我们鉴定出一种与mRNA对应的cDNA，该mRNA在体内对TA肌肉施加七天被动拉伸后表达增加。这种944bp的新型小鼠转录本主要在心肌和骨骼肌中表达，在脑中表达较少。该转录本的翻译揭示了一个85个氨基酸的开放阅读框，编码一个核定位信号和两个重叠的酪蛋白激酶II磷酸化位点。该基因被称为“小肌肉蛋白（X染色体）”（Smpx；HGMW批准的人类基因符号SMPX），我们推测它在骨骼肌肥大中起作用。
