Role of membrane-associated Ca+ dependent matrix metalloprotease-2 in the oxidant activation of Ca2+Atpase by tertiary butylhydroperoxide.

Treatment of bovine pulmonary artery smooth muscle plasma membrane suspension with the oxidant tert-butylhydroperoxide (t-buOOH) increases Ca2+ATPase activity. The smooth muscle plasma membrane possesses a Ca2+ dependent protease activity in the gelatin containing zymogram having an apparent molecular mass of 72 kDa. The 72 kDa protease activity was found to be inhibited by EGTA and the tissue inhibitor of metalloprotease-2 (TIMP-2). Since 72 kDa is the molecular mass of MMP-2 and since in our present study the 72 kDa protease in the gelatin containing zymogram is inhibited by matrix metalloprotease inhibitors, EGTA and TIMP-2, it may be suggested that the 72 kDa protease is the MMP-2. In addition to the increasing Ca2+ATPase activity, t-buOOH also enhances the activity of the membrane associated Ca2+ dependent protease that degrades 14C-gelatin. The oxidant triggered protease activity and the Ca2+ATPase activity were found to be prevented by the antioxidant vitamin E, and also by the Ca2+ dependent matrix metalloprotease inhibitors: EGTA and TIMP-2. Adding MMP-2 to the smooth muscle plasma membrane suspension caused an increase in Ca2+ATPase activity and pretreatment with TIMP-2 prevents the increase in Ca2+ATPase activity. Combined treatment of the smooth muscle plasma membrane with low doses of MMP-2 and t-buOOH augments further the Ca2+ATPase activity caused by the respective doses of either t-buOOH or MMP-2. Pretreatment with TIMP-2 prevents the increase in Ca2+ATPase activity elicited by the low doses of MMP-2 and/or t-buOOH.