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Cathepsin B localizes to plasma membrane caveolae of differentiating myoblasts and is secreted in an active form at physiological pH.

Authors: Jane, DT  Morvay, L  Dasilva, L  Cavallo-Medved, D  Sloane, BF  Dufresne, MJ 
Citation: Jane DT, etal., Biol Chem. 2006 Feb;387(2):223-34.
Pubmed: (View Article at PubMed) PMID:16497156
DOI: Full-text: DOI:10.1515/BC.2006.030

Our in vitro studies support a functional link between the induction of cathepsin B gene expression and the catabolic restructuring associated with myotube formation during myogenesis in vivo. We have tested two predictions that are basic to this hypothesis: (1) that active cathepsin B is localized to plasma membrane caveolae of fusing myoblasts; and (2) that active cathepsin B is secreted from fusing myoblasts at physiological pH. During differentiation, L6 rat myoblasts demonstrated a fusion-related increase in activity associated with the 25/26-kDa, fully processed, active form of cathepsin B. Immunocytochemical studies demonstrated a redistribution of lysosomal cathepsin B protein toward the membrane of fusing myoblasts, and a colocalization of cathepsin B with caveolin-3, the muscle-specific structural protein of membrane caveolae. Sucrose density fractionation and Western blot analysis demonstrated that an active form of cathepsin B localizes to caveolar fractions along with caveolin-3, annexin-VII, beta-dystroglycan and dystrophin. Finally, 'real-time' activity assays and Western blot analysis demonstrated that active cathepsin B is secreted from fusing myoblasts at physiological pH. Collectively, these studies support an association of active cathepsin B with plasma membrane caveolae and the secretion of active cathepsin B from differentiating myoblasts during myoblast fusion.

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CRRD Object Information
CRRD ID: 1599532
Created: 2007-02-07
Species: All species
Last Modified: 2007-02-07
Status: ACTIVE



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RGD is funded by grant HL64541 from the National Heart, Lung, and Blood Institute on behalf of the NIH.