RESUMEN
BACKGROUND: Epstein-Barr virus (EBV) infection may be necessary for the development of Multiple sclerosis (MS). Earlier we had identified six MS risk loci that are co-located with binding sites for the EBV transcription factor Epstein-Barr Nuclear Antigen 2 (EBNA2) in EBV-infected B cells (lymphoblastoid cell lines - LCLs). METHODS: We used an allele-specific chromatin immunoprecipitation PCR assay to assess EBNA2 allelic preference. We treated LCLs with a peptide inhibitor of EBNA2 (EBNA2-TAT), reasoning that inhibiting EBNA2 function would alter gene expression at these loci if it was mediated by EBNA2. FINDINGS: We found that EBNA2 binding was dependent on the risk allele for five of these six MS risk loci (p < 0·05). Treatment with EBNA2-TAT significantly altered the expression of TRAF3 (p < 0·05), CD40 (p < 0·001), CLECL1 (p <0·0001), TNFAIP8 (p < 0·001) and TNFRSF1A (p < 0·001). INTERPRETATION: These data suggest that EBNA2 can enhance or reduce expression of the gene depending on the risk allele, likely promoting EBV infection. This is consistent with the concept that these MS risk loci affect MS risk through altering the response to EBNA2. Together with the extensive data indicating a pathogenic role for EBV in MS, this study supports targeting EBV and EBNA2 to reduce their effect on MS pathogenesis. FUNDING: Funding was provided by grants from MS Research Australia, National Health and Medical Research Council of Australia, Australian Government Research Training Program, Multiple Sclerosis International Federation, Trish Multiple Sclerosis Research Foundation.
Asunto(s)
Antígenos Nucleares del Virus de Epstein-Barr/metabolismo , Esclerosis Múltiple/genética , Factores de Transcripción/metabolismo , Alelos , Proteínas Reguladoras de la Apoptosis/genética , Proteínas Reguladoras de la Apoptosis/metabolismo , Linfocitos B/metabolismo , Linfocitos B/virología , Células Cultivadas , Herpesvirus Humano 4/genética , Herpesvirus Humano 4/metabolismo , Herpesvirus Humano 4/patogenicidad , Humanos , Lectinas Tipo C/genética , Lectinas Tipo C/metabolismo , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Esclerosis Múltiple/virología , Unión Proteica , Receptores Tipo I de Factores de Necrosis Tumoral/genética , Receptores Tipo I de Factores de Necrosis Tumoral/metabolismo , Factor 3 Asociado a Receptor de TNF/genética , Factor 3 Asociado a Receptor de TNF/metabolismoRESUMEN
Activation of phosphatidylinositol 3-kinase (PI3K) is an early and essential step in interleukin-2 receptor (IL-2R) signalling, and plays an important role in regulating both cell survival and cellular proliferation. In the present study, we utilized Baf-B03 cells expressing mutated IL-2R to examine the contribution of PI3K to proliferative capacity. In this model IL-2-mediated induction of the downstream PI3K-dependent signalling molecule p70 S6 kinase was detected, but there was no proliferative response. Increasing the level of PI3K activity by transfection of an active form of the catalytic subunit, p110*, enabled the proliferative capacity of the mutated receptor. Whereas, in cells without p110*, IL-2 lacked the capacity to induce c-myc and to overcome an S-phase checkpoint, S-phase transition was restored by transfection of p110*, and this was accompanied by an increase in the c-myc response. Despite the presence of p110*, activity cells still required IL-2R-derived signals for proliferation, and IL-2Rbeta truncated at amino acid 350 were sufficient to provide this signalling activity. The data support a model in which the level of available PI3K can determine the cellular response to IL-2.