Release of metabolic enzymes by Giardia in response to interaction with intestinal epithelial cells.
Giardia lamblia, an important cause of diarrheal disease, resides in the small intestinal lumen in close apposition to epithelial cells. Since the disease mechanisms underlying giardiasis are poorly understood, elucidating the specific interactions of the parasite with the host epithelium is likely to provide clues to understanding the pathogenesis. Here we tested the hypothesis that contact of Giardia lamblia with intestinal epithelial cells might lead to release of specific proteins. Using established co-culture models, intestinal ligated loops and a proteomics approach, we identified three G. lamblia proteins (arginine deiminase, ornithine carbamoyl transferase and enolase), previously recognized as immunodominant antigens during acute giardiasis. Release was stimulated by cell-cell interactions, since only small amounts of arginine deiminase and enolase were detected in the medium after culturing of G. lamblia alone. The secreted G. lamblia proteins were localized to the cytoplasm and the inside of the plasma membrane of trophozoites. Furthermore, in vitro studies with recombinant arginine deiminase showed that the secreted Giardia proteins can disable host innate immune factors such as nitric oxide production. These results indicate that contact of Giardia with epithelial cells triggers metabolic enzyme release, which might facilitate effective colonization of the human small intestine.
Ringqvist
Emma
E
Department of Cell and Molecular Biology, BMC, Uppsala University, Uppsala, Sweden.
Palm
J E Daniel
JE
Skarin
Hanna
H
Hehl
Adrian B
AB
Weiland
Malin
M
Davids
Barbara J
BJ
Reiner
David S
DS
Griffiths
William J
WJ
Eckmann
Lars
L
Gillin
Frances D
FD
Svärd
Staffan G
SG
D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology; D018920:Coculture Techniques; D003593:Cytoplasm / Q000201:enzymology; D015180:Electrophoresis, Gel, Two-Dimensional; D004847:Epithelial Cells / Q000469:parasitology*; D016829:Giardia lamblia / Q000201:enzymology* / Q000276:immunology; D006801:Humans; D006867:Hydrolases / Q000302:isolation & purification / Q000378:metabolism; D009569:Nitric Oxide / Q000037:antagonists & inhibitors; D009954:Ornithine Carbamoyltransferase / Q000302:isolation & purification / Q000378:metabolism; D010751:Phosphopyruvate Hydratase / Q000302:isolation & purification / Q000378:metabolism; D040901:Proteomics; D015800:Protozoan Proteins / Q000302:isolation & purification* / Q000378:metabolism*; D053058:Trophozoites / Q000201:enzymology
D015800:Protozoan Proteins; D009569:Nitric Oxide; D009954:Ornithine Carbamoyltransferase; D006867:Hydrolases; C019723:arginine deiminase; D010751:Phosphopyruvate Hydratase