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Constitutive phosphorylation of interferon receptor A-associated signaling proteins in systemic lupus erythematosus.


ABSTRACT:

Background

Overexpression of type I interferon (IFN-I)-induced genes is a common feature of systemic lupus erythematosus (SLE) and its experimental models, but the participation of endogenous overproduction of IFN-I on it is not clear. To explore the possibility that abnormally increased IFN-I receptor (IFNAR) signaling could participate in IFN-I-induced gene overexpression of SLE, we examined the phosphorylation status of the IFNAR-associated signaling partners Jak1 and STAT2, and its relation with expression of its physiologic inhibitor SOCS1 and with plasma levels of IFN? and IFN-like activity.

Methodology/principal findings

Peripheral blood mononuclear cells (PBMC) from SLE patients with or without disease activity and healthy controls cultured in the presence or in the absence of IFN? were examined by immunoprecipitation and/or western blotting for expression of the two IFNAR chains, Jak1, Tyk2, and STAT2 and their phosphorylated forms. In SLE but not in healthy control PBMC, Jak1 and STAT2 were constitutively phosphorylated, even in the absence of disease activity (basal pJak1: controls vs. active SLE p<0.0001 and controls vs. inactive SLE p = 0.0006; basal pSTAT2: controls vs. active and inactive SLE p<0.0001). Although SOCS1 protein was slightly but significantly decreased in SLE in the absence or in the presence of IFN? (p = 0.0096 to p<0.0001), in SOCS1 mRNA levels were markedly decreased (p = 0.036 to p<0.0001). IFN? induced higher levels of the IFN-I-dependent MxA protein mRNA in SLE than in healthy controls, whereas the opposite was observed for SOCS1. Although there was no relation to increased serum IFN?, active SLE plasma could induce expression of IFN-dependent genes by normal PBMC.

Conclusions/significance

These findings suggest that in some SLE patients IFN-I dependent gene expression could be the result of a low IFNAR signaling threshold.

SUBMITTER: Ramirez-Velez G 

PROVIDER: S-EPMC3408474 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Publications

Constitutive phosphorylation of interferon receptor A-associated signaling proteins in systemic lupus erythematosus.

Ramírez-Vélez Gabriela G   Medina Francisco F   Ramírez-Montaño Luis L   Zarazúa-Lozada Abraham A   Hernández Ramiro R   Llorente Luis L   Moreno José J  

PloS one 20120730 7


<h4>Background</h4>Overexpression of type I interferon (IFN-I)-induced genes is a common feature of systemic lupus erythematosus (SLE) and its experimental models, but the participation of endogenous overproduction of IFN-I on it is not clear. To explore the possibility that abnormally increased IFN-I receptor (IFNAR) signaling could participate in IFN-I-induced gene overexpression of SLE, we examined the phosphorylation status of the IFNAR-associated signaling partners Jak1 and STAT2, and its r  ...[more]

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