Adhesive Basement Membrane (BM) Proteins are Degraded by Plasminogen Activator in the Presence of Plasminogen
The muscle fiber basement membrane (BM) provides tensile strength, ion sieving and scaffolding for regeneration after injury. It serves to keep muscle “satellite” cells interposed between BM and plasma membrane of mammalian muscle fibers. After injury and denervation muscle fibers degenerate or atrophy with activation of stem cells leading to regeneration. Bischoff (1979) showed that in vitro regeneration of single muscle fibers depended on application of neutral proteases to digest the BM. Although recent studies in the frog by McMahan and colleagues (see Sanes 1983) suggest the BM and its components are immutable, other studies in mammals (Gulati et al. 1983) show turn-over of molecules such as fibronectin (Fn; Hynes and Yamada 1982) type IV collagen (coll IV; Timpl et al. 1979a) and laminin (lam; Timpl et al. 1979b). The present study shows that plasmin, generated exogenously or by denervation, degrades BM components with the sensitivity Fn > coll IV > lam. This suggests early participation of the PA-plasmin system in degradation of specific BM components in denervated muscle, in accord with this system’s involvement in tissue remodeling occurring in other situations (see Danø et al. 1985).
KeywordsTrypsin Thrombin Plasminogen Laminin Plasmin
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