The role of C1GALT1C1 in lipopolysaccharide-induced IgA1 aberrant O-glycosylation in IgA nephropathy.
OBJECTIVE
IgA1 aberrant O-glycosylation is one of the main pathogenetic features of IgA nephropathy (IgAN). This study attempted to determine the role of C1GALT1C1 in aberrant IgA1 O-glycosylation induced by lipopolysaccharide (LPS) and identify potential therapeutic targets in IgAN.


METHODS
Lymphocytes isolated from 22 patients with IgAN and 17 normal controls were cultured for 3 to 7 days with or without LPS and 5-azacytidine (5-AZA). Expression levels of C1GALT1C1 mRNA and protein were measured by real-time PCR and Western blot analysis, respectively. Concentration of IgA1 and level of O-glycosylation were determined by ELISA and Vicia villosa (VV) lectin-binding assay. Correlation analysis was performed between the expression of C1GALT1C1 protein and IgA1 O-glycosylation.


RESULTS
Lymphocytes from patients with IgAN secreted more IgA1 than that from normal controls after LPS stimulation (P=0.26, 0.002 and 0.005 on the 3rd, 5th and 7th day, respectively) which could be inhibited by 5-AZA (P=0.001, 0.025 and 0.001 on the 3rd, 5th and 7th day, respectively). Moreover, LPS stimulation could obviously inhibit C1GALT1C1 expression in patients with IgAN (decreased by 71%, 82% and 92% on the 3rd, 5th and 7th day, respectively; P < 0.001), and cause a significant decrease of IgA1 O-glycosylation compared with normal controls (P=0.004, 0.003 and 0.03 on the 3rd, 5th and 7th day, respectively). When 5-AZA was added, the level of C1GALT1C1 expression increased dramatically (1.98, 5.53 and 8.97 times on the 3rd, 5th and 7th day, respectively; P < 0.001) along with an increase of IgA1 O-glycosylation (P=0.295, 0.09 and 0.003 on the 3rd, 5th and 7th day, respectively). However, normal controls showed no significant change in C1GALT1C1 expression and IgA1 O-glycosylation after LPS stimulation (P > 0.05).


CONCLUSIONS
LPS induced IgA1 aberrant O-glycosylation and suppressed C1GALT1C1 expression in patients with IgAN. Upregulation of C1GALT1C1 expression by 5-AZA could reverse the IgA1 aberrant O-glycosylation. These results suggest that C1GALT1C1 may play a key role in the regulation of IgA1 O-glycosylation.
Department of Nephrology, West China Hospital of Sichuan University, Chengdu City, Sichuan Province, China.
Lin-Shen
LS
Xie
Wei
W
Qin
Jun-Ming
JM
Fan
Jun
J
Huang
Xi-Sheng
XS
Xie
Zi
Z
Li
D000293:Adolescent; D000328:Adult; D001374:Azacitidine / Q000378:metabolism; D016022:Case-Control Studies; D002478:Cells, Cultured; D005260:Female; D005922:Glomerulonephritis, IGA / Q000276:immunology* / Q000378:metabolism; D006031:Glycosylation; D006801:Humans; D007070:Immunoglobulin A / Q000276:immunology* / Q000378:metabolism; D008070:Lipopolysaccharides / Q000378:metabolism; D008214:Lymphocytes / Q000378:metabolism; D008297:Male; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D013997:Time Factors; D015854:Up-Regulation / Q000276:immunology; D055815:Young Adult
C505369:C1GALT1C1 protein, human; D007070:Immunoglobulin A; D008070:Lipopolysaccharides; D018832:Molecular Chaperones; D012333:RNA, Messenger; D001374:Azacitidine