Schistosome invasion of human skin and degradation of dermal elastin are mediated by a single serine protease |
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Authors: | Salter J P Lim K C Hansell E Hsieh I McKerrow J H |
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Affiliation: | Department of Pathology and the Biomedical Sciences Graduate Program, University of California, San Francisco, California 94121, USA. |
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Abstract: | Aquatic larvae (cercariae) of the trematode parasite Schistosoma mansoni rapidly penetrate human skin by degrading host proteins including elastin. Two serine proteases, one chymotrypsin-like and the second trypsin-like, have been proposed to be involved. To evaluate the relative roles of these two proteases in larval invasion, both were purified, identified by sequence, and then biochemically characterized. The trypsin-like activity was resolved into two distinct serine proteases 76% similar in predicted amino acid sequence. Southern blot analysis, genomic polymerase chain reaction, and immunolocalization demonstrated that the trypsin-like proteases are in fact not from the schistosome, but are released with larvae from the snail host Biomphalaria glabrata. Invasion inhibition assays using selective inhibitors confirmed that the chymotrypsin-like protease is the enzyme involved in skin penetration. Its ability to degrade skin elastin was confirmed, and the three sites of cleavage within elastin help define a new family of elastases. |
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