Binding of fibronectin by Trichomonas vaginalis is influenced by iron and calcium.
We have reported that Trichomonas vaginalis, the causative agent of the most common, non-viral sexually transmitted disease, bound to cover slips coated with fibronectin (FN) (Crouch & Alderete, Microbiol 1999 145: 2835-43). In this study, we extend that observation by showing that FN binding is specific, and we present data on the requirements of FN binding by T. vaginalis. Immunofluorescence and immuno-gold labelling readily detected FN throughout the trichomonal surface. Parasites bound to(125)I-labelled FN in a time- and concentration-dependent fashion. In the absence of protease inhibitor, iodinated FN was released from the trichomonad surface. Unlabelled FN specifically competed for binding in a concentration-dependent fashion with the(125)I-labelled FN. Interestingly, the amount of FN bound by T. vaginalis organisms was dependent on iron. High-iron-grown trichomonads acquired lower numbers of molecules but with 10-fold higher affinity than low-iron-grown organisms. Further, we show that for iron-replete organisms, calcium (Ca(2+)) at physiological levels increased amounts of bound FN. The increase in binding was rapid, occurring within 5 min of Ca(2+)addition, and required de novo protein synthesis. Co-incubation of live parasites with Ca(2+)in the presence of FN was necessary to increase the amount of FN bound. Treatment of trichomonads with okadaic acid, but not other phosphatase inhibitors, resulted in a 50% decrease in binding of FN, regardless of the presence of Ca(2+), suggesting a role for phosphatase in FN association. These results indicate that depending on the iron status of T. vaginalis organisms in vivo, Ca(2+)may influence trichomonad recognition and binding to FN during host parasitism.
Crouch
M L
ML
Department of Microbiology, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78284-7758, USA.
Benchimol
M
M
Alderete
J F
JF
D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D002118:Calcium / Q000494:pharmacology*; D002448:Cell Adhesion / Q000187:drug effects; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005260:Female; D005353:Fibronectins / Q000378:metabolism* / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D005898:Glass; D006801:Humans; D007501:Iron / Q000494:pharmacology*; D016253:Microscopy, Immunoelectron; D019319:Okadaic Acid / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011480:Protease Inhibitors / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D014176:Protein Biosynthesis; D013379:Substrate Specificity; D014247:Trichomonas Vaginitis / Q000382:microbiology; D014246:Trichomonas vaginalis / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism*
D005353:Fibronectins; D011480:Protease Inhibitors; D019319:Okadaic Acid; D007501:Iron; D010749:Phosphoprotein Phosphatases; D003546:Cysteine Endopeptidases; D002118:Calcium