Matrix metalloproteinases (MMPs) are key regulatory molecules in the formation, remodeling, and degradation of extracellular matrix components in both physiological and pathological processes. However their intracellular presence and activity was also reported. The purpose of this study was to examine the expression and subcellular localization of the gelatinases MMP-2 and MMP-9 in skeletal muscle fibers of normal and physically trained rats. In control hindlimb muscle, the activity and expression of the gelatinases were barely detectable in muscle fibers. In contrast, 5 days after physical training, there was significant upregulation of gelatinolytic activity in myofibers, mainly in their nuclei, and to a lesser extent in sarcoplasm and sarcolemma, as assessed by high resolution in situ zymography. The nuclei of satellite cells did not contained the activity. Within the myonuclei, the gelatinolytic activity was distributed throughout the nuclear interchromatin area. Subcellular fractionation followed by gel zymography revealed that MMP-2, but not MMP-9, is the myonuclear gelatinase whose activation occurs upon training. Training activated and upregulated MMP-9 in the cytoplasm. By RT-PCR, there was significant increase in MMP-9 mRNA only. We conclude that training activates nuclear MMP-2, it also increases both the expression and activity of cytoplasmic/sarcolemmal MMP-9. We suggest that the gelatinases play roles in muscle adaptation to training; MMP-2 may be involved in the processes of nuclear gene expression.
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.