The disintegrins ADAM10 and TACE contribute to the constitutive and phorbol ester-regulated normal cleavage of the cellular prion protein

We showed previously that PrPc undergoes constitutive and phorbol ester-reg ulated cleavage inside the 106-126 toxic domain of the protein, leading to the production of a fragment referred to as N1. Here we show by a pharmacol ogical approach that o-phenanthroline, a general zinc-metalloprotease inhib itors, as well as BB3103 and TAPI, the inhibitors of metalloenzymes ADAM10 (A disintegrin and metalloprotease); and TACE, tumor necrosis factor alpha -converting enzyme; ADAM17), respectively, drastically reduce N1 formation. We set up stable human embryonic kidney 293 transfectants overexpressing h uman ADAM10 and TACE, and we demonstrate that ADAM10 contributes to constit utive N1 roduction whereas TACE mainly participates in regulated N1 formati on. Furthermore, constitutive N1 secretion is drastically reduced in fibrob lasts deficient for ADAM10 whereas phorbol 12,13-dibutyrate-regulated N1 pr oduction is fully abolished in TACE-deficient cells. Altogether, our data d emonstrate for the first time that disintegrins could participate in the ca tabolism of glycosyl phosphoinositide-anchored proteins such as PrPc. Secon d, our study identifies ADAM10 and ADAM17 as the protease candidates respon sible for normal cleavage of PrPc. Therefore, these disintegrins could be s een as putative cellular targets of a therapeutic strategy aimed at increas ing normal PrPc breakdown and thereby depleting cells of the putative 106-1 26 "toxic" domain of PrPc.