Inhibition of Urokinase-type Plasminogen Activator (uPA) Abrogates Myogenesis In Vitro
Inhibition of Urokinase-type Plasminogen Activator (uPA) Abrogates Myogenesis In Vitro
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DOI：
10.1055/s-0038-1656001
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发表时间：
1997-03
影响因子：
6.7
通讯作者：
P. Muñoz-Cánoves;F. Miralles;M. Baiget;Jordi Félez
中科院分区：
文献类型：
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作者：
P. Muñoz-Cánoves;F. Miralles;M. Baiget;Jordi Félez
尿激酶型纤溶酶原激活物（uPA）是血液纤溶级联反应的组成部分之一。uPA是一种广谱蛋白水解酶，参与多种生理病理过程，包括细胞纤溶、粘附、迁移、侵袭和重塑。在这里，我们提供了uPA参与肌生成的证据，这一过程需要剧烈的细胞膜重组，从而从成肌细胞祖细胞产生多核肌管。我们已经解剖了整个不同的生肌区室的uPA的表达，发现在C2 C12成肌细胞中与肌管形成相关的uPA酶活性增加，uPA mRNA在融合和分化开始之前增加。当融合和分化被特异性抑制剂（DMSO，细胞松弛素B）阻断时，uPA水平强烈下调。该过程是可逆的和特异性的：去除抑制剂立即恢复uPA mRNA的水平，而抗uPA抗体对uPA酶活性的特异性抑制导致融合程度降低50%，并消除肌肉特异性基因产物，如α-肌动蛋白和MyoD。此外，在获得MyoD后，成纤维细胞转化为肌肉样细胞导致uPA mRNA的急剧增加，这部分是由于uPA基因的转录激活。这些结果表明，在融合和分化之前，uPA表达的增加通过MyoD介导的机制发生，而正常MyoD表达需要该蛋白酶的纤溶酶原激活依赖性活性。因此，这些研究将生肌因子的影响范围扩展到血液系统的内在成分纤维蛋白溶解。两者合计，一种机制所使用的成肌细胞成为一个分化的肌管，涉及尿激酶的诱导细胞外蛋白水解，提出。
Summary Urokinase-type plasminogen activator (uPA) is one of the components of blood’s fibrinolytic cascade. uPA acts as a broad spectrum proteolytic enzyme involved in different physio-pathological processes including cellular fibrinolysis, adhesion, migration, invasion and remodeling. Here, we present evidence that uPA participates in myogenesis, a process which requires drastic cell membrane reorganization, leading to the plurinucleated myotube from the progenitor myoblast. We have dissected the expression of uPA throughout the different myogenic compartments and found an increase in uPA enzymatic activity associated with myotube formation in C2C12 myoblast cells, with uPA mRNA increasing prior the onset of fusion and differentiation. When both fusion and differentiation were blocked by specific inhibitors (DMSO, cyto-chalasin B) the levels of uPA were strongly downregulated. This process was reversible and specific: the removal of the inhibitors immediately restored the levels of uPA mRNA while the specific inhibition of uPA enzymatic activity by an anti-uPA antibody resulted in a 50% reduction of the extent of fusion and in the abrogation of muscle-specific gene products, such as a-actin and MyoD. Moreover, the conversion of fibroblasts to muscle-like cells upon acquisition of MyoD resulted in a dramatic increase of uPA mRNA, which was partially due to transcriptional activation of the uPA gene. These results indicate that the increase in uPA expression prior to fusion and differentiation occurs via a MyoD-mediated mechanism whereas the normal MyoD expression requires the plasminogen activation-dependent activity of this protease. Therefore, these studies extend the sphere of influence of myogenic factors to fibrinolysis, an intrinsic component of the hematological system. Taken together, one mechanism used by the myoblast cell to become a differentiated myotube, involving the inductive extracellular proteolysis of urokinase, is proposed.