Budasz-Rwiderska M, Jank M, Motyl T
Department of Physiological Sciences, Faculty of Veterinary Medicine, Warsaw Agricultural University, Warsaw, Poland.
J Physiol Pharmacol. 2005 Jun;56 Suppl 3:195-214.
Myostatin (MSTN) and transforming growth factor-beta1 (TGF-beta1) belong to the same TGF-beta superfamily of proteins. They are involved in regulation of skeletal muscle growth and development as well as muscle catabolism. The aim of the present study was to investigate the relationship between MSTN and TGF-beta1 expression in proliferating and differentiating mouse C2C12 myoblasts cultured in normal and catabolic conditions and to evaluate the effect of exogenous TGF-beta1 as well as "knock down" of TGF-beta1 receptor type II on MSTN expression in proliferating and differentiating myogenic cells. The direct effect of TGF-beta1 on myostatin was also examined. Myostatin expression increased gradually with cell confluency in proliferating cultures, while the level of TGF-beta1, detected in the form of a 100 kDa small latent complex diminished. Myostatin expression was accompanied by a partial cell cycle arrest. Three forms of myostatin were found: a 52 kDa precursor, a 40 kDa latency associated propeptide, and a 26 kDa active peptide. A decrease in myostatin and TGF-beta1 levels was observed during the first three days of differentiation, which was subsequently followed by significant increase of their expression during next three to four days of differentiation. Catabolic state induced by dexamethasone significantly increased the level of all forms of myostatin as well as latent (100 kDa) and active (25 kDa) forms of TGF-beta1 in differentiating myoblasts in a dose dependent manner. Exogenous TGF-beta1 (2 ng/ml) significantly increased myostatin levels both in proliferating and differentiating C2C12 myoblasts, whereas silencing of the TGF-beta1 receptor II gene significantly lowered myostatin level in examined cells. The presented results indicate that TGF-beta1 may control myostatin-related regulation of myogenesis through up-regulation of myostatin, predominantly in the course of terminal differentiation and glucocorticoid-dependent catabolic stimulation.
肌肉生长抑制素（MSTN）和转化生长因子-β1（TGF-β1）属于同一类转化生长因子-β超家族蛋白。它们参与骨骼肌生长发育以及肌肉分解代谢的调节。本研究的目的是探讨在正常和分解代谢条件下培养的增殖和分化小鼠C2C12成肌细胞中MSTN与TGF-β1表达之间的关系，并评估外源性TGF-β1以及II型TGF-β1受体“敲低”对增殖和分化的成肌细胞中MSTN表达的影响。还检测了TGF-β1对肌肉生长抑制素的直接作用。在增殖培养物中，肌肉生长抑制素的表达随着细胞汇合度逐渐增加，而以100 kDa小潜伏复合物形式检测到的TGF-β1水平降低。肌肉生长抑制素的表达伴随着部分细胞周期停滞。发现了三种形式的肌肉生长抑制素：52 kDa前体、40 kDa潜伏相关前肽和26 kDa活性肽。在分化的前三天观察到肌肉生长抑制素和TGF-β1水平降低，随后在接下来的三到四天分化过程中其表达显著增加。地塞米松诱导的分解代谢状态以剂量依赖的方式显著增加了分化的成肌细胞中所有形式的肌肉生长抑制素以及潜伏（100 kDa）和活性（25 kDa）形式的TGF-β1的水平。外源性TGF-β1（2 ng/ml）显著增加了增殖和分化的C2C12成肌细胞中的肌肉生长抑制素水平，而TGF-β1受体II基因的沉默显著降低了所检测细胞中的肌肉生长抑制素水平。所呈现的结果表明，TGF-β1可能主要在终末分化和糖皮质激素依赖性分解代谢刺激过程中通过上调肌肉生长抑制素来控制与肌肉生长抑制素相关的肌生成调节。
