Intracellular MMP‐2 Activity in Skeletal Muscle Is Associated With Type II Fibers

Abstract

Matrix metalloproteinase 2 (MMP-2) is a proteolytic enzyme implicated in motility, differentiation and regeneration of skeletal muscle fibers through processing of extracellular substrates. Although MMP-2 has been found to be localized intracellularly in cardiomyocytes where the enzyme is thought to contribute to post-ischemic loss of contractility, little is known about intracellular MMP-2 activity in skeletal muscle fibers. In the present study we demonstrate intracellular MMP-2 in normal skeletal muscle by immunohistochemical staining. Immunogold electron microscopic analyses indicated that the enzyme was concentrated in Z-lines of the sarcomers, in the nuclear membrane and in mitochondria. By use of in situ zymography, we found that gelatinolytic activity in muscle fibers was colocalized with immunofluorecent staining for MMP-2. Staining for MMP-9, the other member of the gelatinase group of the MMPs, was negative. The broad-spectrum metalloprotease inhibitor EDTA and the selective gelatinase inhibitor CTT2, but not the cysteine inhibitor E64, strongly reduced the gelatinolytic activity. The intracellular gelatinolytic activity was much more prominent in fast twitch type II fibers than in slow twitch type I fibers, and there was a decrease in intracellular gelatinolytic activity and MMP-2 expression in muscles from mice exposed to high intensity interval training. Together our results indicate that MMP-2 is part of the intracellular proteolytic network in normal skeletal muscle, especially in fast twitch type II fibers. Further, the results suggest that intracellular MMP-2 in skeletal muscle fibers is active during normal homeostasis, and affected by level of physical activity.3

A high resolution atlas of gene expression in the domestic sheep (Ovis aries)

“…Numerous genes with structural, motor and regulatory functions were highly expressed in BFxT compared to Texel bicep muscle, with approximately 5- to 18-fold expression increases for various members of the collagen ( COL1A1 , COL1A2 , COL3A1 ) and myosin families ( MYH2 , MYL4 ), along with CSRP3 (a mechanosensor) [98], FMOD (fibromodulin, a regulator of fibrillogenesis) [99], keratocan ( KERA , a proteoglycan involved in myoblast differentiation) [100], matrix metalloproteinase 2 ( MMP2 , a proteolytic enzyme associated with muscle regeneration) [101], and calsequestrin 2 ( CASQ2 , one of the most abundant Ca 2+ -binding proteins in the sarcoplasmic reticulum, essential for muscle contraction) [102].…”

Effects of Resistance Training Volume on MMPs in Circulation, Muscle and Adipose Tissue

“…Deus et al [10] analyzed the tibialis anterior muscle which is primarily fast-twitch in rats [33], while our study used gastrocnemius muscle. Recently, Hadler-Olsen et al [12] reported that the predominance of glycolytic fibers favors the increase in enzyme activity. However, evidence suggests that the gastrocnemius muscle is more oxidative than the tibialis anterior [34].…”

Novel intracellular N‐terminal truncated matrix metalloproteinase‐2 isoform in skeletal muscle ischemia‐reperfusion injury

“…Recently, intracellular localization of MMP‐2 has been reported in various cell types and injury models . Our previous studies with H9C2 cardiomyocytes demonstrated that the NTT‐MMP‐2 isoform was generated by oxidative stress‐mediated activation of an alternate promoter within the first intron of the MMP‐2 gene .…”

“…Recently, intracellular localization of MMP-2 has been reported in various cell types and injury models. [27][28][29] Our previous studies with H9C2 cardiomyocytes demonstrated that the NTT-MMP-2 isoform was generated by oxidative stress-mediated activation of an alternate promoter within the first intron of the MMP-2 gene. 17,18 NTT-MMP-2 lacks both the secretory sequence and the inhibitory prodomain, and thus remains exclusively intracellular and is enzymatically active.…”