Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.22.54 (calpain 3)
 430 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Chicken cystatin and human kininogen domain 2 are members of the cystatin superfamily of protein-type cysteine proteinase inhibitors. They show structural and functional similarities, but only human kininogen domain 2 inhibits calpain. Using recombinant chicken cystatin as a scaffold for hybrid cassette analysis, the known reactive-site regions (N-terminus, first hairpin loop and second hairpin loop) were substituted by the corresponding sequences of human kininogen domain 2 in a single and combined manner. Seven hybrids were expressed, purified to homogeneity, characterized protein-chemically, and their inhibition of papain, actinidin, human cathepsin B, human cathepsin L and calpain (80-kDa subunit of rabbit skeletal muscle calpain II and porcine erthrocyte calpain 1) was determined. Strong but temporary inhibition of calpain by chicken cystatin hybrids carrying the N-terminus alone (variant sc1-KD2) or the N-terminus together with the first hairpin loop (variant sc1/2-KD2) was observed; hybrids of the second hairpin loop (sc3-KD2, sc1/3-KD2, sc2/3-KD2, sc1/2/3-KD2) were less strong calpain inhibitors. These data indicate that the inhibiton of calpain by human kininogen domain 2 requires the correct conformation and combination of several contact sites, and suggest that the N-terminus and the first hairpin loop play a major role in this ensemble. Remarkably, hybrid sc2-KD2 exhibited 5 or 150 times stronger inhibition of actinidin compared to native chicken cystatin or to proteolytically isolated human kininogen domain 2, respectively. This indicates an important role of the first hairpin loop of cystatins in the interaction with actinidin. Along with the impaired inhibition of cathepsin L, papain, actinidin, cathepsin B and calpain by the hybrids sc1/3-KD2, sc2/3-KD2 and sc1/2/3-KD2, these results support our hypothesis that all three predicted contact regions of kininogen domain 2 contribute to binding in the active-site clefts of papain-like enzymes in a finely balanced manner.
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PMID:Hybrids of chicken cystatin with human kininogen domain 2 sequences exhibit novel inhibition of calpain, improved inhibition of actinidin and impaired inhibition of papain, cathepsin L and cathepsin B. 865 98

Calpain-3 deficiency leads to muscular dystrophy in humans and mice and to perturbation of the NFkappaB/IkappaB pathway. As this phenotype is mainly atrophic, this study was performed to determine whether protein turnover and/or proteolytic gene expression was altered in muscles following calpain-3 deficiency. In vitro rates of protein turnover and of substrate ubiquitination, cathepsin B and B+L activities, and mRNA levels for several proteolytic genes were measured in skeletal muscles from 4-5 month-old control and calpain-3 knockout mice. Rates of protein synthesis and breakdown, cathepsin activities, and rates of substrate ubiquitination remained stable in muscles from calpain-3 deficient mice. However, and surprisingly, mRNA levels for cathepsin L, the 14-kDa ubiquitin-conjugating enzyme E2, and the C2 subunit of the 20S proteasome decreased by approximately 47% (P<0.005) in the gastrocnemius muscle from calpain-3 deficient mice. In contrast, muscle mRNA levels for ubiquitin and subunit S5a of the 26S proteasome were unaffected by calpain-3 deficiency. Taken together these data demonstrate that the expression of some genes that are involved in distinct proteolytic pathways is selectively and coordinately down-regulated without any effect on proteolysis. This suggests new pathophysiological hypotheses, e.g. a lack of maturation of NFkappaB precursor and/or a defect in specific substrate targeting.
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PMID:Down-regulation of genes in the lysosomal and ubiquitin-proteasome proteolytic pathways in calpain-3-deficient muscle. 1267 59