title: Haplotype-independent costimulation of IL-10 secretion by SDF-1/CXCL12 proceeds via AP-1 binding to the human IL-10 promoter.
abstract: Costimulation by the chemokine, stromal cell-derived factor-1 (SDF-1)/CXCL12, has been shown to increase the amount of IL-10 secreted by TCR-stimulated human T cells; however, the molecular mechanisms of this response are unknown. Knowledge of this signaling pathway may be useful because extensive evidence indicates that deficient IL-10 secretion promotes autoimmunity. The human IL-10 locus is highly polymorphic. We report in this study that SDF-1 costimulates IL-10 secretion from T cells containing all three of the most common human IL-10 promoter haplotypes that are identified by single-nucleotide polymorphisms at -1082, -819, and -592 bp (numbering is relative to the transcription start site). We further show that SDF-1 primarily costimulates IL-10 secretion by a diverse population of CD45RA(-) ("memory") phenotype T cells that includes cells expressing the presumed regulatory T cell marker, Foxp3. To address the molecular mechanisms of this response, we showed that SDF-1 costimulates the transcriptional activities in normal human T cells of reporter plasmids containing 1.1 kb of all three of the common IL-10 promoter haplotypes. IL-10 promoter activity was ablated by mutating two nonpolymorphic binding sites for the AP-1 transcription factor, and chromatin immunoprecipitation assays of primary human T cells revealed that SDF-1 costimulation enhances AP-1 binding to both of these sites. Together, these results delineate the molecular mechanisms responsible for SDF-1 costimulation of T cell IL-10 secretion. Because it is preserved among several human haplotypes and in diverse T cell populations including Foxp3(+) T cells, this pathway of IL-10 regulation may represent a key mechanism for modulating expression of this important immunoregulatory cytokine.
authors.affiliation: Department of Immunology, Mayo Clinic College of Medicine, Mayo Clinic, Rochester, MN 55905, USA.
authors.forename: Kimberly N
authors.initials: KN
authors.lastname: Kremer
authors.forename: Ashok
authors.initials: A
authors.lastname: Kumar
authors.forename: Karen E
authors.initials: KE
authors.lastname: Hedin
mesh_terms: D001665:Binding Sites / Q000235:genetics; D002478:Cells, Cultured; D054377:Chemokine CXCL12; D019743:Chemokines, CXC / Q000502:physiology*; D006239:Haplotypes; D006801:Humans; D016753:Interleukin-10 / Q000235:genetics* / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D013601:T-Lymphocytes / Q000737:chemistry; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: C515255:CXCL12 protein, human; D054377:Chemokine CXCL12; D019743:Chemokines, CXC; D018808:Transcription Factor AP-1; D016753:Interleukin-10