Role of Muscle Proteinases in Maintenance of Muscle Integrity and Mass

Abstract

Current evidence indicates that, of the thirteen known lysosomal peptide hydrolases, only seven, cathepsins A, B, C, D, H, L, and lysosomal carboxypeptidase B are located inside skeletal muscle cells. Only one of the reported neutral and alkaline proteases is located inside skeletal muscle cells', this neutral protease is the Ca2+‐dependent proteinase, CAF. With the possible exception of cathepsin N, which can degrade collagen, it seems probable that any protease that contributes to postmortem tenderization needs to be located inside muscle cells. Because very little degradation of myosin or actin occurs in postmortem muscle, most of the small amount of proteolytic degradation of the myofibrillar proteins that occurs during postmortem storage must be due to CAF, which is unique in being unable to degrade myosin and actin. It is not certain that postmortem proteolysis by CAF causes increased tenderness; some recently discovered actin‐fragmenting proteins could be involved.

The calpain system and skeletal muscle growth

“…The large size and highly ordered structure of intact myofibrils (1-2 µm in diameter and extending the entire length of the cell, up to several mm) would prevent them being taken up into lysosomes (Lowell et al 1986) or from entering the central channel containing the active sites of the proteasome (multicatalytic protease). Indeed, neither myofibrils nor structurally recognizable fragments of myofibrils have been observed in lysosomal structures, even in rapidly atrophying muscle (Goll et al 1989), and the proteasome has no effect on myofibrillar proteins when they are in the myofibrillar structure (Koohmaraie 1992;Solomon and Goldberg 1996). Both lysosomal cathepsins and the proteasome, however, rapidly degrade individual myofibrillar proteins under the appropriate conditions.…”

“…This review will focus on the role of the calpain system in skeletal muscle growth. It was originally proposed that the calpain system was responsible for initiating metabolic turnover of the myofibrillar proteins and that it therefore affected only rate of muscle protein degradation (Dayton et al 1975;Goll et al 1983Goll et al , 1992b. Recent studies, however, have shown that calpain activity is required for myoblast fusion (Balcerzak et al 1995;Barnoy et al 1997;Kumar et al 1992;Kwak et al 1993a,b;Temm-Grove et al 1999) and for cell proliferation (Mellgren 1997;Watanabe et al 1989;Zhang et al 1997) in addition to cell growth (Mellgren et al 1994).…”

“…Many studies involving treatments designed to increase rate of muscle growth have simply used measurements of live animal or carcass weight to evaluate the efficacy of the treatments used, and the effects of these treatments on the three basic factors determining muscle growth have not been determined. Studies attempting to improve the nutritional status of animals are likely to increase the rate of muscle protein synthesis, but may also affect rate of muscle protein degradation (Goll et al 1989;Reeds et al 1986). Indeed, differences in rates of muscle growth in domestic animals often are due to differences in rate of muscle protein degradation with little or no change in rate of protein synthesis (Bohorov et al 1987;Maruyama et al 1978;Reeds et al 1986).…”

Effects of stress hormone cortisol on the mRNA expression of myogenenin, MyoD, Myf5, PAX3 and PAX7

“…The total amount of muscle mass depends on the rate of protein synthesis and protein degradation in the animals (Goll et al 1983). Reduction in protein degradation is the best way to improve the growth of farm animals.…”

Salado y descongelado simultáneo en salmuera para la obtención de jamón curado de cerdo de raza ibérica.

“…Son enzimas activadas por calcio y son las responsables de la degradación de proteínas como: troponina I, tropomiosina, proteina C, desminina, titina y nebulina (Goll et al, 1983;Koohmaraie, 1994). La actividad de este tipo de enzimas desaparece después de la etapa de salado (Sárraga, 1992;Rosell et al, 1996) 1.6.1.2.…”