Serum- and Glucocorticoid-Inducible Kinase 1 Sensitive NF-κB Signaling in Dendritic Cells

• Published in: Cellular physiology and biochemistry Vol. 34; no. 3; pp. 943 - 954
• Main Authors: Schmid, Evi, Xuan, Nguyen Thi, Zahir, Naima, Russo, Antonella, Yang, Wenting, Kuhl, Dietmar, Faggio, Caterina, Shumilina, Ekaterina, Lang, Florian
• Format: Journal Article
• Language: English
• Published: Basel, Switzerland Cell Physiol Biochem Press GmbH & Co KG 01.01.2014
• Subjects: Animals; Base Sequence; Cell Cycle Proteins - metabolism; Cell Differentiation; Dendritic Cells - enzymology; Dendritic Cells - immunology; Dendritic Cells - metabolism; DNA Primers; IKKα/β; Immediate-Early Proteins - metabolism; Intracellular Signaling Peptides and Proteins - metabolism; Mice; Mice, Inbred C57BL; Mice, Knockout; NDRG1; NF-kappa B - metabolism; NF-κB; Original Paper; Phagocytosis; Phosphorylation; PI3 kinase; Protein-Serine-Threonine Kinases - metabolism; Real-Time Polymerase Chain Reaction; Up-Regulation; NF-κB; IKKα/β; PI3 kinase; NDRG1; Phagocytosis
• ISSN: 1015-8987; 1421-9778
• DOI: 10.1159/000366311

Background/Aims: Dendritic cells (DCs), antigen-presenting cells linking innate and adaptive immunity, are required for initiation of specific T cell-driven immune responses. Phosphoinositide-3-kinase (PI3K) suppresses proinflammatory cytokine production in DCs, which limits T helper (Th1) polarization. PI3K is in part effective by downregulation of transcription factor NF-κB. Downstream signaling elements of PI3K include serum- and glucocorticoid-inducible kinase 1 (SGK1) and its phosphorylation target N-myc downstream regulated gene 1 (NDRG1). The present study explored whether SGK1 and NDRG1 play a role in the regulation of NF-κB and DC-maturation. Methods: DCs were isolated from bone marrow (BMDCs) or spleen of mice lacking functional SGK1 (sgk1 -/- ) and corresponding wild type mice (sgk1 +/+ ). Protein abundance was determined by Western blotting. Transcription was inhibited by siRNA. Abundance of maturation markers was quantified by flow cytometry. FITC-dextran uptake was determined to quantify phagocytosis. Results: NDRG1 was similarly expressed in sgk1 +/+ and sgk1 -/- BMDCs, but SGK1-dependent phosphorylation of NDRG-1 was decreased in sgk1 -/- BMDCs. Silencing of NDRG1 in sgk1 +/+ BMDCs as compared to control empty vector-treated BMDCs enhanced nuclear abundance of NF-κB subunit p65. Moreover, the abundance of phosphorylated NF-κB inhibitor IκBa, of phosphorylated IκB kinase (IKKa/ß) and of nuclear p65 were significantly higher in sgk1 -/- BMDCs than in sgk1 +/+ BMDCs. Expression of maturation markers, MHC II, and CD86, was significantly larger and phagocytic capacity was significantly lower in sgk1 -/- than in sgk1 +/+ BMDCs. Expression of CD86 and MHCII was also significantly higher in DCs isolated from the spleen of sgk1 -/- mice than those from sgk1 +/+ mice. Conclusion: SGK1 and NDRG1 participate in the regulation of NF-κB signaling in and maturation of DCs.