title: Glucocorticoid receptors on and in a unicellular organism, Cryptobia salmositica.
abstract: This is the first report to our knowledge that demonstrates a functional steroid hormone receptor in a protozoon. The study used Cryptobia salmositica, a pathogenic haemoflagellate found in salmonid fishes. It has been previously shown that cortisol and dexamethasone (a synthetic glucocorticoid) enhanced the multiplication of C. salmositica under in vitro conditions indicating the presence of glucocorticoid receptors on/in the parasite. Also, the glucocorticoid receptor antagonist, mifepristone (RU486), inhibited the stimulatory effect of the two glucocorticoids on parasite multiplication. In the present study, we used an antibody (produced in a rabbit against glucocorticoid receptor protein) agglutination test and confocal microscopy with immunohistofluorescence staining to demonstrate cortisol-glucocorticoid receptor-like protein receptors on the plasma membrane and in the cytoplasm of the parasite. In two in vitro studies, the addition of 50ngml(-1) of RU486 was more effective in inhibiting parasite replication in cultures with 7,000parasitesml(-1) than in cultures with 14,000parasitesml(-1). Also, 100ngml(-1) of RU486/ml was more effective than 50ngml(-1) in inhibiting parasite multiplication in the 14,000 parasitesml(-1) cultures. These in vitro studies indicate that the number of binding sites on/in the parasite is finite. The findings may be important in future studies especially on steroid receptor signalling pathways and dissection of ligand-receptor interactions, and for evaluating the adaptations that develop in pathogens as part of the host-parasite interaction.
authors: Department of Integrative Biology, University of Guelph, Guelph, ON N1G 2W1, Canada. Electronic address: mao@uoguelph.ca.
authors: Mao
authors: M
authors: Li
authors: Department of Integrative Biology, University of Guelph, Guelph, ON N1G 2W1, Canada.
authors: Patrick T K
authors: PT
authors: Woo
mesh_terms: D000372:Agglutination Tests; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology; D056986:Euglenozoa Infections / Q000469:parasitology / Q000662:veterinary; D005393:Fish Diseases / Q000469:parasitology; D006854:Hydrocortisone / Q000494:pharmacology; D016830:Kinetoplastida / Q000187:drug effects / Q000378:metabolism* / Q000472:pathogenicity; D008856:Microscopy, Fluorescence; D015735:Mifepristone / Q000494:pharmacology; D015800:Protozoan Proteins / Q000378:metabolism*; D011817:Rabbits; D011965:Receptors, Glucocorticoid / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012487:Salmonidae / Q000469:parasitology; D015398:Signal Transduction
chemical_list: D015800:Protozoan Proteins; D011965:Receptors, Glucocorticoid; D015735:Mifepristone; D003907:Dexamethasone; D006854:Hydrocortisone
keywords: Cortisol; Cryptobia salmositica; Glucocorticoid receptor (GR); Host–parasite interaction; In vitro culture; Protozoan; RU486