Down-regulation of core 1 beta1,3-galactosyltransferase and Cosmc by Th2 cytokine alters O-glycosylation of IgA1.
BACKGROUND
Patients with IgA nephropathy (IgAN) have an increased amount of abnormally O-glycosylated IgA1 in circulation, in glomerular deposits and produced by tissue cells in vitro. Although increased production of Th2 cytokines by peripheral blood lymphocytes and a functional abnormality of core 1 β1,3-galactosyltransferase (C1β3Gal-T) have been proposed as mechanisms underlying pathogenesis of IgAN, they are still obscure and are not connected.


METHODS
To clarify the effect of T-cell cytokines, we analysed the mRNA levels of C1β3Gal-T and its molecular chaperone Cosmc, C1β3Gal-T activity and subsequent O-glycosylation of IgA1 in a human B-cell line stimulated with these cytokines. The surface IgA1-positive human B-cell line was cultured with recombinant human IFN-γ, IL-2, IL-4 or IL-5. The production and glycosylation of IgA1 were determined by sandwich ELISA and enzyme-linked lectin binding assay, respectively. The mRNA levels of C1β3Gal-T and Cosmc were quantitatively measured by real-time PCR. C1β3Gal-T activity was analysed using high-performance liquid chromatography.


RESULTS
IgA1 production by IL-4-stimulated cells was significantly higher than controls or after IFN-γ or IL-5. The terminal glycosylation of secreted IgA1 was altered in response to IL-4. IL-4 stimulation significantly decreased the mRNA levels of both C1β3Gal-T and Cosmc and of C1β3Gal-T activity. IL-4 stimulation was clearly blocked by recombinant human IL-4 soluble receptor.


CONCLUSIONS
It appears that Th2 cytokine IL-4 may play a key role in controlling glycosylation of the IgA1 hinge region.
Yamada
Koshi
K
Division of Nephrology, Department of Internal Medicine, Juntendo University Faculty of Medicine, Tokyo, Japan.
Kobayashi
Noriyoshi
N
Ikeda
Tomomi
T
Suzuki
Yusuke
Y
Tsuge
Toshinao
T
Horikoshi
Satoshi
S
Emancipator
Steven N
SN
Tomino
Yasuhiko
Y
D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism / Q000494:pharmacology*; D015536:Down-Regulation / Q000502:physiology*; D005700:Galactosyltransferases / Q000378:metabolism; D005922:Glomerulonephritis, IGA / Q000378:metabolism / Q000473:pathology; D006031:Glycosylation / Q000187:drug effects; D006801:Humans; D007070:Immunoglobulin A / Q000378:metabolism*; D015847:Interleukin-4 / Q000378:metabolism / Q000494:pharmacology; D016393:Lymphoma, B-Cell / Q000378:metabolism / Q000473:pathology; D018832:Molecular Chaperones / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism
C505369:C1GALT1C1 protein, human; D016207:Cytokines; D007070:Immunoglobulin A; D018832:Molecular Chaperones; D012333:RNA, Messenger; D015847:Interleukin-4; D005700:Galactosyltransferases; C076385:glycoprotein-N-acetylgalactosamine 3-beta-galactosyltransferase