Differential Regulation of CCL22 Gene Expression in Murine Dendritic Cells and B Cells

Abstract

The activated T cell-attracting CC chemokine CCL22 is expressed by stimulated B cells and mature dendritic cells (DC). We have cloned and sequenced the complete mouse gene, including 4 kb of the 5′-flanking promoter region, and detected two distinct sites for initiation of transcription by 5′-RACE. Reporter gene assays indicate that the promoter reflects the specificity of the endogenous gene. Within the proximal promoter region, we identified potential binding sites for NF-κB, Ikaros, and a putative GC box. All three regions bind proteins. The NF-κB site was shown to specifically bind NF-κB subunits p50 and p65 from nuclear extracts of LPS-stimulated B cells, B cell line A20/2J, TNF-α-stimulated bone marrow-derived DC, and DC line XS106. Furthermore, promoter activity was affected by targeted mutagenesis of the NF-κB site and transactivation with p50 and p65. The region harboring the putative Ikaros site contributes to promoter activity, but the binding protein does not belong to the Ikaros family. The GC box was shown to specifically bind Sp1 using extracts from LPS-stimulated B cells and A20/2J but not from DC and DC line XS106. Additionally, Sp1 transactivated the promoter in A20/2J but not in XS106 cells, and mutation of the Sp1 site diminished transactivation. Furthermore, binding of the protein complex at the GC box is required for NF-κB activity, and the spatial alignment of the binding sites is of critical importance for promoter activity. Thus, identical and distinct proteins contribute to expression of CCL22 in DC and B cells.

Targeted knock down of CCL22 and CCL17 by siRNA during DC differentiation and maturation affects the recruitment of T subsets

“…The transcriptional regulation of CCL22 and CCL17 is similar to T helper chemokines like CCL3, CCL4, CCL5 and CXCL10 in several cell types (Grove and Plumb 1993;Ohmori et al 1997;Fernandez 2002;Hiroi and Ohmori 2003;Ghadially et al 2005). Therefore, targeting LPS-induced signal transduction pathways during DC differentiation and maturation might, in addition to blocking either NF-kB or STAT family member activation, reduces all cytokine and chemokine production, including immune-stimulating effector types (Sallusto et al 1999;Langenkamp et al 2000;Xu et al 2007).…”

B cells responses and cytokine production are regulated by their immune microenvironment

“…The additional signaling can be provided by the immune microenvironment and specific differentiation stages of the B cell. For example, the main cytokines produced by naïve B cells upon activation are the chemokines CCL22 and CCLl7 [119–121]. These two chemokines share the same receptor (CCR4), which is strongly expressed in CD4 + Th2 type T cells.…”

Effects of formoterol and salmeterol on the production of Th1- and Th2-related chemokines by monocytes and bronchial epithelial cells

“…The finding that IkB-a expression was suppressed by salmeterol in the present study suggests that b 2 -adrenoreceptor-cAMP pathway activation may enhance LPS-induced NF-kB expression via suppression of IkB-a expression in monocytes. Within the proximal promoter region of MDC, potential binding sites for NF-kB subunits p50 and p65 have been identified [30]. Thus, LABAs may suppress IkB-a expression and cause translocation of NF-kB into the nucleus by increasing cAMP and subsequently transactivating the promoter of the MDC gene.…”