Background: Dendritic cells (DC) are the most potent antigen presenting cells (APC) of the immune system. Prostaglandin E2, cyclic AMP, and protein kinase A (PKA) have all been shown to regulate DC maturation and activity. In other cells, the ability to these molecules to convey their signals has been shown to be dependent on A-kinase achoring proteins (AKAPS). Here we present evidence for the existence and functional importance of AKAPs in human DC. Methodolog/Principal Findings: Using immunofluorescence and/or western analyses we identify AKAP79, AKAP149, AKAP95, AKAP LBC and Ezrin: We also demonstrate by western analysis that expression of AKAP79, AKAP149 and RII are upregulated with DC differentiation and maturation. We establish the functional importance of PKA anchoring in multiple aspects of DC biology using the anchoring inhibitor peptides Ht31 and AKAP-15. Incubation of protein or peptide antigen loaded DC with Ht31 or AKAP-IS results in a 30-50% decrease in antigen presentation as measured by IFN-γ production from antigen specific CD4+ T cells. Incubation of LPS treated DC with Ht31 results in 80% inhibition of TNF-α and IL-10 production. Ht31 slightly decreases the expression of CD18 and CD11a and CD11b; slightly increases the basal expression of CD83, dramatically decreases the LPS stimulated expression of CD40, CD80 and CD83, and significantly increases the expression of the chemokine receptor CCR7. Conclusions: These experiments represent the first evidence for the functional importance of PKA anchoring in multiple aspects of DC biology.
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