TY - JOUR
T1 - K-RAS GTPase- and B-RAF kinase-mediated T-cell tolerance defects in rheumatoid arthritis
AU - Singh, Karnail
AU - Deshpande, Pratima
AU - Li, Guangjin
AU - Yu, Mingcan
AU - Pryshchep, Sergey
AU - Cavanagh, Mary
AU - Weyand, Cornelia M.
AU - Goronzy, Jörg J.
PY - 2012/6/19
Y1 - 2012/6/19
N2 - Autoantibodies to common autoantigens and neoantigens, such as IgG Fc and citrullinated peptides, are immunological hallmarks of rheumatoid arthritis (RA). We examined whether a failure in maintaining tolerance is mediated by defects in T-cell receptor activation threshold settings. RA T cells responded to stimulation with significantly higher ERK phosphorylation (P < 0.001). Gene expression arrays of ERK pathway members suggested a higher expression of KRAS and BRAF, which was confirmed by quantitative PCR (P = 0.003), Western blot, and flow cytometry (P < 0.01). Partial silencing of KRAS and BRAF lowered activation-induced phosphorylated ERK levels (P < 0.01). In individual cells, levels of these signaling molecules correlated with ERK phosphorylation, attesting that their concentrations are functionally important. In confocal studies, B-RAF/K-RAS clustering was increased in RA T cells 2 min after T-cell receptor stimulation (P < 0.001). Overexpression of B-RAF and K-RAS in normal CD4 T cells amplified polyclonal T-cell proliferation and facilitated responses to citrullinated peptides. We propose that increased expression of B-RAF and K-RAS lowers T-cell activation thresholds in RA T cells, enabling responses to autoantigens.
AB - Autoantibodies to common autoantigens and neoantigens, such as IgG Fc and citrullinated peptides, are immunological hallmarks of rheumatoid arthritis (RA). We examined whether a failure in maintaining tolerance is mediated by defects in T-cell receptor activation threshold settings. RA T cells responded to stimulation with significantly higher ERK phosphorylation (P < 0.001). Gene expression arrays of ERK pathway members suggested a higher expression of KRAS and BRAF, which was confirmed by quantitative PCR (P = 0.003), Western blot, and flow cytometry (P < 0.01). Partial silencing of KRAS and BRAF lowered activation-induced phosphorylated ERK levels (P < 0.01). In individual cells, levels of these signaling molecules correlated with ERK phosphorylation, attesting that their concentrations are functionally important. In confocal studies, B-RAF/K-RAS clustering was increased in RA T cells 2 min after T-cell receptor stimulation (P < 0.001). Overexpression of B-RAF and K-RAS in normal CD4 T cells amplified polyclonal T-cell proliferation and facilitated responses to citrullinated peptides. We propose that increased expression of B-RAF and K-RAS lowers T-cell activation thresholds in RA T cells, enabling responses to autoantigens.
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U2 - 10.1073/pnas.1117640109
DO - 10.1073/pnas.1117640109
M3 - Article
C2 - 22615393
AN - SCOPUS:84862538572
SN - 0027-8424
VL - 109
SP - E1629-E1637
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 25
ER -