SCHISTOSOMA-MANSONI - EVIDENCE FOR A 28-6TDA MEMBRANE-ANCHORED PROTEASE ON SCHISTOSOMULA

Transformation of cercariae of Schistosoma mansoni into schistosomula is accompanied by release of a soluble 28-kDa serine protease (s28) fr om the acetabular glands. The postulated activities of s28 include cle avage of skin connective tissue proteins (elastin, etc.), release of t he cercarial glycocalyx, and cleavage of complement proteins. Our prev ious results demonstrated the presence of an antigenically cross-react ive protein on the surface of mechanically transformed schistosomula. As shown here, schistosomula express on their surface a 28-kDa serine protease (m28) which can be immunoprecipitated with anti-s28 antibodie s. m28 eluted from the schistosomular tegumental membrane with NP-40 w as purified to homogeneity in one step by adsorption on a chymotrypsin inhibitor column: 6-aminocaproyl-D-tryptophan methyl ester-Sepharose. Proteolytic activity of m28 was completely inhibited by the chymotryp sin inhibitor N-succinyl-Ala-Ala-Pro-Phe-chloromethyl ketone. Efficien t removal of m28 from schistosomula was achieved with NP-40, deoxychol ate, cholate, Tween 20, and phospholipases A(2) and C, but not with pa pain, trypsin, pronase, or proteinase K. Furthermore, treatment with p hosphatidyl inositol-specific phospholipase C (PI-PLC) followed by hyd roxylamine also released m28. Anti-cross-reactive determinant antibodi es which recognize a neo epitope exposed in glycosyl phosphatidyl inos itol-containing molecules cleaved by PI-PLC bind to purified m28. The latter results suggest that m28 is anchored to the tegumental membrane of schistosomula by a lipid anchor and that perhaps some of the m28 m olecules are bound via glycosylphosphatidyl inositol. Based on inhibit or sensitivity and antigenic cross-reactivity, it is conceivable that s28 and m28 are related, if not identical, proteins. Finally, m28 was detected antigenically also on lung-stage and adult worms of S. manson i. (C) 1996 Academic Press, Inc.