Meprin A, composed of α and β subunits, is a membrane-bound
metalloproteinase in renal proximal tubules.
Meprin A plays an important role in tubular epithelial cell injury during
acute kidney injury (AKI). The present study demonstrated that during
ischemia-reperfusion-induced AKI,
meprin A was shed from proximal tubule membranes, as evident from its redistribution toward the basolateral side, proteolytic processing in the membranes, and excretion in the urine. To identify the
proteolytic enzyme responsible for shedding of
meprin A, we generated stable HEK cell lines expressing
meprin β alone and both
meprin α and
meprin β for the expression of
meprin A.
Phorbol 12-myristate 13-acetate and
ionomycin stimulated ectodomain shedding of
meprin β and
meprin A. Among the inhibitors of various
proteases, the broad spectrum inhibitor of the ADAM family of
proteases,
tumor necrosis factor-α
protease inhibitor (TAPI-1), was most effective in preventing constitutive,
phorbol 12-myristate 13-acetate-, and
ionomycin-stimulated shedding of
meprin β and
meprin A in the medium of both transfectants. The use of differential inhibitors for ADAM10 and ADAM17 indicated that ADAM10 inhibition is sufficient to block shedding. In agreement with these results,
small interfering RNA to ADAM10 but not to ADAM9 or ADAM17 inhibited
meprin β and
meprin A shedding. Furthermore, overexpression of ADAM10 resulted in enhanced shedding of
meprin β from both transfectants. Our studies demonstrate that ADAM10 is the major ADAM
metalloproteinase responsible for the constitutive and stimulated shedding of
meprin β and
meprin A. These studies further suggest that inhibiting ADAM 10 activity could be of therapeutic benefit in AKI.