ISOLATION OF LATENT 31-KDA C-TRUNCATED STROMELYSIN AND 21-KDA STROMELYSIN FROM RABBIT SYNOVIAL FIBROBLASTS - AN ALTERNATIVE ACTIVATION PATHWAY FOR STROMELYSIN

The processing of culture medium of rabbit synovial fibroblasts led to the isolation of three stromelysin-1 (MMP-3) cleavage products: A 31- kDa protein, which represents a C-truncated latent stromelysin-1, an a ctive stromelysin-1 of 21 kDa, that originates from the 31-kDa proform by activation. A third protein had a molecular mass of 25 kDa represe nting the C-terminal part of prostromelysin-1 and is missing in the C- truncated latent stromelysin-1. The activation process of human prostr omelysin-1 in vitro is known to lead to an active stromelysin-1 with a relative molecular mass of 45 kDa by removing the N-terminal prodomai n. This active stromelysin-1 is further processed to a lower molecular mass active form of 28 kDa. Our results obtained for the highly homol ogous rabbit stromelysin-1 ndicate that another activation pathway is possible. In a first step prostromelysin-1; is hydrolysed between Met( 261)-Glu generating a C-truncated latent stromelysin-1, which is activ ated by cleavage of the Thr(83)-Phe bond to the 21-kDa stromelysin-1. The latent C-truncated stromelysin-1 is slowly converted even at 4 deg rees C into the active form. In the presence of 50 mu M ZnCl2 this act ivation was prevented for at least three weeks. The activation rate is largely enhanced by aminophenylmercury acetate and especially by tryp sin. The differences of the 21-kDa stromelysin-1 to a 28-kDa stromelys in-1 isolated from human rheumatoid synovial fluids described earlier are discussed.