Gut-associated immunolocalization of the Schistosoma mansoni cysteine proteases, SmCL1 and SmCL2

Transcripts encoding discrete, cathepsin L-like cysteine proteases, known a s SmCL1 and SmCL2. have been reported from the adult stages of the human bl ood fluke Schistosoma,mansoni. However. the physiological roles of these 2 enzymes and their natural substrates remain uncertain and controversial. To determine their localization in adult S.mansoni by immunocytochemical proc edures, and thereby to gain insight into their likely functions, polymerase chain reaction-based cDNAs encoding mature SmCL1 and SmCL2 were ligated in to Escherichia coli. The bacterially expressed recombinant proteins: (bSmSL 1, bSmCL2) were used to generate monospecific rabbit antisera. For light mi croscopy, paraffin-embedded sections were visualized with the fluorophore C y3. For transmission electron microscopy (TEM). LR White-embedded tissue wa s visualized with 15 nm gold. Under light microscopy. fluorescence was visi ble on the luminal surface of the gastrodermis in both sexes for both prote ins. For bSmCL1 and bSmCL2. TEM revealed gold particles primarily associate d with amorphous deposits within superficial digestive vacuoles on the gast rodermal surface of males and females. Some bSmCL1 reaction product was obs erved in vesicles within the gastrodermis, and very sparsegastrodermal acti vity was observed with bSmCL2. By contrast, neither enzyme was immunolocali zed in the reproductive organs, vitelline glands, nor gynecorphoric canal. The gut-associated immunolocalization of SmCL1 and SmCL2 indicates that bot h these endopepridases participate in hemoglobin proteolysis.