Trypanosoma cruzi: Cruzipain and membrane-bound cysteine proteinase isoform(s) interacts with human α₂ -macroglobulin and pregnancy zone protein

Plasmatic levels of pregnancy zone protein (PZP) increase in children with acute Chagas disease. PZP, as well as α₂-macroglobulin (α2-M), are able to interact with Trypanosoma cruzi proteinases. The interaction of α2-M and PZP with cruzipain, the major cysteine proteinase of T. cruzi, was investigated. Several molecular changes on both α-M inhibitors under reaction with cruzipain were found. PAGE analysis showed: (i) formation of complexes of intermediate mobility and tetramerization of native α2-M and PZP, respectively; (ii) limited proteolysis of bait region in α2-M and PZP, and (iii) covalent binding of cruzipain to PZP and α₂-M. Conformational and structural changes experimented by α-Ms correlate with modifications of the enzyme electrophoretic mobility and activity. Cruzipain-α-M complexes were also detected by gelatin SDS-PAGE and immunoblotting using polyclonal anti-cruzipain antibodies. Concomitantly, α2-M and PZP impaired the activity of cruzipain towards Bz-Pro-Phe-Arg-pNA substrate. In addition, α-Ms were able to form covalent complexes with membrane isoforms of cysteine proteinases cross-reacting with cruzipain. The present study suggests that both human α-macroglobulin inhibitors could prevent or minimize harmful action of cruzipain on host's molecules and hypothetically regulate parasite functions controlled by cruzipain.