Distinct protein kinase A anchoring proteins direct prostaglandin E 2 modulation of toll-like receptor signaling in alveolar macrophages

Abstract

Toll-like receptors (TLRs) direct a proinflammatory program in macrophages. One mediator whose generation is induced by TLR ligation is prostaglandin E2 (PGE2), which is well known to increase intracellular cAMP upon G protein-coupled receptor ligation. How PGE2/cAMP shapes the nascent TLR response and the mechanisms by which it acts remain poorly understood. Here we explored PGE2/cAMP regulation of NO production in primary rat alveolar macrophages stimulated with the TLR4 ligand LPS. Endogenous PGE2 synthesis accounted for nearly half of the increment in NO production in response to LPS. The enhancing effect of PGE2 on LPS-stimulated NO was mediated via cAMP, generated mainly upon ligation of the E prostanoid 2 receptor and acting via protein kinase A (PKA) rather than via the exchange protein activated by cAMP. Isoenzyme-selective cAMP agonists and peptide disruptors of protein kinase A anchoring proteins (AKAPs) implicated PKA regulatory subunit type I (RI) interacting with an AKAP in this process. Gene knockdown of potential RI-interacting AKAPs expressed in alveolar macrophages revealed that AKAP10 was required for PGE2 potentiation of LPS-induced NO synthesis. AKAP10 also mediated PGE2 potentiation of the expression of cytokines IL-10 and IL-6, whereas PGE2 suppression of TNF-α was mediated by AKAP8-anchored PKA-RII. Our data illustrate the pleiotropic manner in which G protein-coupled receptor-derived cAMP signaling can influence TLR responses in primary macrophages and suggest that AKAP10 may coordinate increases in gene expression. © 2011 by The American Society for Biochemistry and Molecular Biology, Inc.