Abstract
Dendritic cells (DCs), the main antigen‐presenting cells, induce type II helper T cell (Th2) immune responses, but the mechanism by which this occurs is not fully elucidated. Mice that have a CD11c (DC)‐specific deletion of the Gnas gene (CD11cΔGnas), which encodes the α subunit of the heterotrimeric (αβγ) G protein Gαs, display very low basal cyclic AMP (cAMP) concentrations and an allergic phenotype; the decrease in cAMP and protein kinase A (PKA) activation biases DCs to provoke a Th2 response ex vivo and in vivo (Lee et al., PNAS 112: 1529–34 [2015]). In order to assess how cells compensate for a chronic decrease in cAMP/PKA signaling, we compared the mRNA expression of cAMP pathway components in WT and CD11cΔGnas bone marrow‐derived DCs (BMDCs). Using quantitative real‐time PCR (qPCR), we found that BMDCs from CD11cΔGnas mice have decreased expression of numerous cyclic nucleotide phosphodiesterases (PDEs) that degrade cAMP including PDE4B and 4D, but no overall increase in Gαi proteins or the cAMP transporter MRP4/ABCC4. Treatment of the mouse dendritic cell line DC2.4 with a cell‐permeable PKA‐specific cAMP analog and the Gαs agonist prostaglandin E2 increased PDE4B and 4D expression >2‐fold, indicating the dynamic changes in PDE4B and 4D expression are in response to cellular cAMP concentration. We also assessed the expression of G protein‐coupled receptors (GPCRs; assayed by qPCR‐based Taqman GPCR arrays), including those that regulate cAMP formation. We found a greater number and larger increase in expression for GPCRs that couple to Gαi (rather than other Gα proteins) in CD11cΔGnas BMDCs compared to BMDCs from WT mice. Additionally, expression of multiple PKA subunits (RIIα, RIIβ) decreased >50% in CD11cΔGnas BMDCs. A‐kinase anchor protein (AKAP)6 and AKAP3 have an increase and decrease, respectively, in those BMDCs. Together, these data indicate that DCs with lower cAMP levels have altered expression of both “upstream” cAMP signaling components (GPCRs) and “downstream” components that regulate cAMP levels (PDE isoforms) and actions (PKA subunits, AKAPs). Such changes in expression of GPCRs and post‐G protein components likely reflect withdrawal of “basal”, tonic effects of cAMP, may contribute to the greater Th2 responses and allergic asthma of CD11cΔGnas mice, and may be novel therapeutic targets for allergic asthma.Support or Funding InformationSupported by NIH grants R56AI110505 and T32GM007752.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Published Version
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