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LTBP‐1 blockade in dioxin receptor‐null mouse embryo fibroblasts decreases TGF‐β activity: Role of extracellular proteases plasmin and elastase
Author(s) -
GomezDuran Aurea,
MuleroNavarro Sonia,
Chang Xiaoqing,
FernandezSalguero Pedro M.
Publication year - 2005
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.20637
Subject(s) - proteases , plasmin , elastase , extracellular , transforming growth factor , thrombospondin 1 , chemistry , extracellular matrix , microbiology and biotechnology , protease , neutrophil elastase , small interfering rna , receptor , biology , biochemistry , enzyme , transfection , cancer research , immunology , inflammation , gene , angiogenesis
In mouse embryonic fibroblasts (MEF) lacking dioxin receptor (AhR), high levels of latent transforming growth factor‐β (TGF‐β)‐binding protein‐1 (LTBP‐1) correlated with increased TGF‐β1 activity, an observation suggesting that LTBP‐1 could contribute to maintain TGF‐β1 levels. Here, using small interfering RNAs (siRNA), we have first analyzed if LTBP‐1 expression affected TGF‐β1 activity in MEF cells. We have then determined how LTBP‐1 levels could alter the activity of extracellular proteases known to activate TGF‐β1, and finally, whether protease inhibition could reduce TGF‐β1 activation. LTBP‐1 inhibition by siRNA in AhR−/− MEF decreased the amount of active TGF‐β1 and reduced plasminogen activators (PA)/plasmin and elastase activities and thrombospondin‐1 (TSP‐1) expression, without significantly affecting their mRNA levels. On the contrary, LTBP‐1 siRNA restored matrix metalloproteinase‐2 (MMP‐2) activity in AhR−/− MEF. Interestingly, whereas a TGF‐β1 neutralizing antibody mimicked many of the LTBP‐1 siRNA effects on extracellular proteases, addition of recombinant TGF‐β1 protein increased proteases activity over basal levels in AhR−/− MEF. These proteases contributed to TGF‐β activation since their specific inhibitors reduced active TGF‐β levels in these cells. These results suggest that LTBP‐1 contributes to TGF‐β1 activation in MEF, possibly by influencing the activities of PA/plasmin, elastase, TSP‐1, and MMP‐2. TGF‐β1, on the other hand, could be also involved in maintaining the activity of these extracellular proteases. Thus, LTBP‐1 appears to play a role in TGF‐β1 activation through a process involving extracellular protease activities, which, in turn, could be affected by TGF‐β1 levels. J. Cell. Biochem. © 2005 Wiley‐Liss, Inc.