Disease relevance of Capn3

• Although neither its physiological function nor its in vivo substrates are known, C3 must be an important protein for normal muscle function as mutations in the C3 gene result in limb-girdle muscular dystrophy type 2A [1].
• Muscle-specific calpain, p94, is degraded by autolysis immediately after translation, resulting in disappearance from muscle [2].
• These results may be related to recent findings about the role of p94 gene mutations in limbgirdle muscular dystrophy type 2A [3].
• Recombinant Lp85 and Lp82 were separately expressed using the baculovirus system and partially purified using Co2+ affinity and DEAE chromatographies [4].
• Sepsis induced in rats by cecal ligation and puncture resulted in increased gene expression of micro-calpain, m-calpain, and p94 and in Z-band disintegration in the extensor digitorum longus muscle [5].

High impact information on Capn3

• These results suggested that Lp82 might regulate other calpain activities and cause hydrolysis of substrates such as crystallins during lens cataract formation [6].
• Lp82 also hydrolyzed calpastatin [6].
• Calpastatin inhibited calpain 2 activity, but not Lp82 [6].
• To examine this apparent discrepancy between the amounts of mRNA and protein, wild-type p94 was expressed in COS cells [2].
• Moreover, when site-directed mutagenesis was introduced to change the presumed active-site cysteine of p94 to serine or alanine, the mutated p94 proteins were highly expressed like the IS2-deleted mutants [2].

Biological context of Capn3

• When translated, the Lp82 mRNA would code for protein containing the usual cysteine active site residues and calcium-binding domains [7].
• CsA treatment blocked calpain-3 gene expression rise induced by 10 days of cryolesion [8].
• A different exon 1 (as in lens Lp82 calpain) was present, and exons 15 and 16 in the unique IS2 region of muscle p94 were deleted [9].
• Purification of native p94 was possible with an antibody-affinity column but only as an inactive enzyme; p94(C129S) was purified as a homodimer [10].
• The autolysis sites in p94 clearly showed a different specificity relative to the autolytic and proteolytic cleavage sites of the ubiquitous mu- and m-calpains, in its preference for residues at the P3 to P1' sites, indicating a distinct substrate specificity and function for the muscle enzyme [10].

Anatomical context of Capn3

• Cotransfection experiments in COS-7 cells confirm that C3 can cleave the C-terminus of FLNC in live cells [1].
• Rat skeletal muscle fractions were screened by two anti-peptide antibodies raised against two specific sequences in p94, but the p94 protein could not be found [2].
• We showed by quantitative RT-PCR analysis that mu-calpain, m-calpain, and calpain 3 mRNAs were expressed in satellite cell cultures in proliferating myoblasts (day 3) and differentiating cultures (days 7 and 12) [11].
• After an antisense oligodeoxyribonucleotide treatment with p94, ultrastructural studies show dramatic perturbations in differentiated myotubes and during myofibrillogenesis, mainly involving myofibrillar stability and Z-line integrity [3].
• In pancreatic juice, both proteins appear as a complex of high molecular mass (180 kDa) containing at least one each of p94 and BSDL molecules, interacting by hydrophobic forces [12].

Associations of Capn3 with chemical compounds

• Unlike m-calpain-mediated proteolysis, Lp82-mediated proteolysis was not inhibited by the oral administration of aminoguanidine (AG), which acts to prevent lens opacification [13].
• Interestingly enough, RGTA and heparin, which both strongly increased differentiation, reduced the expression of the mu- and m-calpains and slightly increased that of calpain 3 in differentiating cultures [11].
• PURPOSE: To measure changes in levels of Lp82 during maturation and selenite cataract formation in rat lens [14].

Regulatory relationships of Capn3

• These data suggest that Lp82-induced proteolysis in rodent lenses may occur even in the presence of calpastatin [15].

Other interactions of Capn3

• These results suggest that (1) calpain-3 has a differential role in the early and late stages of regeneration in a calcineurin-dependent manner, and (2) atrogin-1 is involved in the early stages of regeneration independently of calcineurin [8].
• Also, Lp82 and calpain 2 were found to hydrolyze each other [6].
• CONCLUSIONS: Lp82 is a lens-specific calpain [7].
• Activity of endogenous Lp82 against vimentin was also tested by in vitro incubation of rat lens soluble and insoluble fractions with calcium [15].

Analytical, diagnostic and therapeutic context of Capn3

• We then used the anti-calpain 3 antibodies together with antibodies directed against cell-type-specific proteins to determine by double- and triple-labelling immunocytochemistry if the protease is expressed in specific cell populations of rat as well as lesser mouse lemur (Microcebus murinus) brain [16].
• Lp82 protein was detected by immunoblotting or by ELISA after DEAE-5PW chromatography using a polyclonal antibody generated to a peptide sequence in Lp82 [17].
• Northern blot analysis assessed expression of Lp82 mRNA [17].
• The proteolytic profiles of alphaA-crystallin by Lp82 and m-calpain during cataractogenesis in SCR lenses were analyzed by Western blotting and immunohistochemical staining [13].
• We therefore studied the expression of microcalpain (mu-calpain), millicalpain (m-calpain), and calpain 3 in the course of differentiation of these satellite cell cultures in the absence or in the presence of heparin or of a mimic compound (the RGTA RG1282) [11].

References