期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 279, 期 4, 页码 2761-2771出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M308789200
关键词
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p94 (also called calpain 3) is the skeletal muscle-specific calpain and is considered to be a modulator protease in various cellular processes. Analysis of p94 at the protein level is an urgent issue because the loss of p94 protease activity causes limb-girdle muscular dystrophy type 2A. In this study, we enzymatically characterized one alternatively spliced variant of p94, p94: exons 6-15-16-(p94Delta), which lacks two of the p94-specific insertion sequences. In contrast to p94, which has hardly been studied enzymatically due to its rapid, thorough, and apparently Ca2+-independent autolytic activity, p94Delta was stably expressed in COS and insect cells. p94Delta showed Ca2+-dependent caseinolytic and autolytic activities and an inhibitor spectrum similar to those of the conventional calpains. However, calpastatin did not inhibit p94Delta and is a substrate for p94Delta, which is consistent with the properties of p94, presenting p94 as a possible regulator of the conventional calpain system. We also established a semi-quantitative fluorescence resonance energy transfer assay using the calpastatin sequence specifically to measure p94 activity. This method detects the activity of COS-expressed p94 and p94Delta, suggesting that it has potential to evaluate p94 activity in vivo and in the diagnosis of limb-girdle muscular dystrophy type 2A.
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