title: Calpain 3 is activated through autolysis within the active site and lyses sarcomeric and sarcolemmal components.
abstract: Calpain 3 (Capn3) is known as the skeletal muscle-specific member of the calpains, a family of intracellular nonlysosomal cysteine proteases. This enigmatic protease has many unique features among the calpain family and, importantly, mutations in Capn3 have been shown to be responsible for limb girdle muscular dystrophy type 2A. Here we demonstrate that the Capn3 activation mechanism is similar to the universal activation of caspases and corresponds to an autolysis within the active site of the protease. We undertook a search for substrates in immature muscle cells, as several lines of evidence suggest that Capn3 is mostly in an inactive state in muscle and needs a signal to be activated. In this model, Capn3 proteolytic activity leads to disruption of the actin cytoskeleton and disorganization of focal adhesions through cleavage of several endogenous proteins. In addition, we show that titin, a previously identified Capn3 partner, and filamin C are further substrates of Capn3. Finally, we report that Capn3 colocalizes in vivo with its substrates at various sites along cytoskeletal structures. We propose that Capn3-mediated cleavage produces an adaptive response of muscle cells to external and/or internal stimuli, establishing Capn3 as a muscle cytoskeleton regulator.
authors.affiliation: Généthon, CNRS UMR-8115, 1 rue de l'Internationale, 91000 Evry, France.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Taveau
authors.forename: Nathalie
authors.initials: N
authors.lastname: Bourg
authors.forename: Guillaume
authors.initials: G
authors.lastname: Sillon
authors.forename: Carinne
authors.initials: C
authors.lastname: Roudaut
authors.forename: Marc
authors.initials: M
authors.lastname: Bartoli
authors.forename: Isabelle
authors.initials: I
authors.lastname: Richard
mesh_terms: D000199:Actins / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001329:Autolysis; D002154:Calpain / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020134:Catalytic Domain; D002478:Cells, Cultured; D064211:Connectin; D003285:Contractile Proteins / Q000378:metabolism; D003598:Cytoskeletal Proteins; D003599:Cytoskeleton / Q000201:enzymology; D004789:Enzyme Activation; D064448:Filamins; D066298:In Vitro Techniques; D051379:Mice; D008840:Microfilament Proteins / Q000378:metabolism; D008954:Models, Biological; D009124:Muscle Proteins / Q000378:metabolism; D018482:Muscle, Skeletal / Q000201:enzymology*; D041681:NIH 3T3 Cells; D010750:Phosphoproteins / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012508:Sarcolemma / Q000201:enzymology; D012518:Sarcomeres / Q000201:enzymology; D013379:Substrate Specificity; D016608:Talin / Q000378:metabolism; D000099149:Ezrin
chemical_list: D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D002154:Calpain; D064211:Connectin; D003285:Contractile Proteins; D003598:Cytoskeletal Proteins; D064448:Filamins; D008840:Microfilament Proteins; D009124:Muscle Proteins; D010750:Phosphoproteins; D011494:Protein Kinases; D011994:Recombinant Proteins; D016608:Talin; D000099149:Ezrin; C486523:SORBS3 protein, human; C117452:Sorbs3 protein, mouse; C577285:TTN protein, human; C491373:Capn3 protein, mouse