title: Surfactant Protein A Enhances Constitutive Immune Functions of Clathrin Heavy Chain and Clathrin Adaptor Protein 2.
abstract: NF-κB transcription factors are key regulators of pulmonary inflammatory disorders and repair. Constitutive lung cell type- and microenvironment-specific NF-κB/inhibitor κBα (IκB-α) regulation, however, is poorly understood. Surfactant protein (SP)-A provides both a critical homeostatic and lung defense control, in part by immune instruction of alveolar macrophages (AMs) via clathrin-mediated endocytosis. The central endocytic proteins, clathrin heavy chain (CHC) and the clathrin adaptor protein (AP) complex AP2, have pivotal alternative roles in cellular homeostasis that are endocytosis independent. Here, we dissect endocytic from alternative functions of CHC, the α-subunit of AP2, and dynamin in basal and SP-A-modified LPS signaling of macrophages. As revealed by pharmacological inhibition and RNA interference in primary AMs and RAW264.7 macrophages, respectively, CHC and α-adaptin, but not dynamin, prevent IκB-α degradation and TNF-α release, independent of their canonical role in membrane trafficking. Kinetics studies employing confocal microscopy, Western analysis, and immunomagnetic sorting revealed that SP-A transiently enhances the basal protein expression of CHC and α-adaptin, depending on early activation of protein kinase CK2 (former casein kinase II) and Akt1 in primary AMs from rats, SP-A(+/+), and SP-A(-/-) mice, as well as in vivo when intratracheally administered to SP-A(+/+) mice. Constitutive immunomodulation by SP-A, but not SP-A-mediated inhibition of LPS-induced NF-κB activity and TNF-α release, requires CHC, α-adaptin, and dynamin. Our data demonstrate that endocytic proteins constitutively restrict NF-κB activity in macrophages and provide evidence that SP-A enhances the immune regulatory capacity of these proteins, revealing a previously unknown pathway of microenvironment-specific NF-κB regulation in the lung.
authors.affiliation: Divisions of 1 Cellular Pneumology and.
authors.forename: Christina
authors.initials: C
authors.lastname: Moulakakis
authors.affiliation: 2 Microbial Interface Biology, Research Center Borstel, Leibniz Center for Medicine and Biosciences, Borstel, Germany; and.
authors.forename: Christine
authors.initials: C
authors.lastname: Steinhäuser
authors.affiliation: Divisions of 1 Cellular Pneumology and.
authors.forename: Dominika
authors.initials: D
authors.lastname: Biedziak
authors.affiliation: Divisions of 1 Cellular Pneumology and.
authors.forename: Katja
authors.initials: K
authors.lastname: Freundt
authors.affiliation: 2 Microbial Interface Biology, Research Center Borstel, Leibniz Center for Medicine and Biosciences, Borstel, Germany; and.
authors.forename: Norbert
authors.initials: N
authors.lastname: Reiling
authors.affiliation: Divisions of 1 Cellular Pneumology and.|3 Department of Anesthesiology and Intensive Care Medicine, University of Lübeck, Lübeck, Germany.
authors.forename: Cordula
authors.initials: C
authors.lastname: Stamme
mesh_terms: D033962:Adaptor Protein Complex 2 / Q000276:immunology*; D000818:Animals; D047390:Casein Kinase II / Q000378:metabolism; D002478:Cells, Cultured; D033922:Clathrin Heavy Chains / Q000276:immunology*; D004705:Endocytosis / Q000187:drug effects; D006801:Humans; D018189:Immunomagnetic Separation; D016676:Macrophages, Alveolar / Q000187:drug effects / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D000072000:NF-KappaB Inhibitor alpha / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D059748:Proteolysis / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D037662:Pulmonary Surfactant-Associated Protein A / Q000494:pharmacology*; D000067996:RAW 264.7 Cells; D034741:RNA, Small Interfering / Q000378:metabolism; D017207:Rats, Sprague-Dawley; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D033962:Adaptor Protein Complex 2; D037662:Pulmonary Surfactant-Associated Protein A; D034741:RNA, Small Interfering; D014409:Tumor Necrosis Factor-alpha; D033922:Clathrin Heavy Chains; D000072000:NF-KappaB Inhibitor alpha; D047390:Casein Kinase II; D051057:Proto-Oncogene Proteins c-akt
keywords: IκB-α/NF-κB; adaptor protein complex 2; alveolar macrophages; clathrin heavy chain; surfactant protein A