Rap1 induces cytokine production in pro-inflammatory macrophages through NFκB signaling and is highly expressed in human atherosclerotic lesions.
Repressor activator protein 1 (Rap1) is essential for maintaining telomere length and structural integrity, but it also exerts other non-telomeric functions. The present study tested the hypothesis that Rap1 is released into the cytoplasm and induces production of pro-inflammatory cytokines via nuclear factor kappa B (NFκB) signaling in macrophages, a cell type involved in the development and progression of atherosclerotic lesions. Western blotting analysis confirmed that Rap1 was present in the cytoplasm of differentiated human monocytic leukemia cells (THP-1, a macrophage-like cell line). Co-immunoprecipitation assay revealed a direct interaction between Rap1 and I kappa B kinase (IKK). Knockdown of Rap1 suppressed lipopolysaccharide-mediated activation of NFκB, and phosphorylation of inhibitor of kappa B α (IκBα) and p65 in THP-1 macrophages. The reduction of NFκB activity was paralleled by a decreased production of NFκB-dependent pro-inflammatory cytokines and an increased expression of IκBα (native NFκB inhibitor) in various macrophage models with pro-inflammatory phenotype, including THP-1, mouse peritoneal macrophages and bone marrow-derived M1 macrophages. These changes were observed selectively in pro-inflammatory macrophages but not in bone marrow-derived M2 macrophages (with an anti-inflammatory phenotype), mouse lung endothelial cells, human umbilical vein endothelial cells or human aortic smooth muscle cells. Immunostaining revealed that Rap1 was localized mainly in macrophage-rich areas in human atherosclerotic plaques and that the presence of Rap1 was positively correlated with the advancement of the disease process. In pro-inflammatory macrophages, Rap1 promotes cytokine production via NFκB activation favoring a pro-inflammatory environment which may contribute to the development and progression of atherosclerosis.
a Department of Pharmacology and Pharmacy and State Key Laboratory of Pharmaceutical Biotechnology ; Li Ka Shing Faculty of Medicine; The University of Hong Kong ; Hong Kong , China.
Yin
Y
Cai
b Division of Cardiovascular Medicine; Brigham and Women's Hospital; Harvard Medical School ; Boston , MA USA.
Galina K
GK
Sukhova
a Department of Pharmacology and Pharmacy and State Key Laboratory of Pharmaceutical Biotechnology ; Li Ka Shing Faculty of Medicine; The University of Hong Kong ; Hong Kong , China.
Hoi Kin
HK
Wong
a Department of Pharmacology and Pharmacy and State Key Laboratory of Pharmaceutical Biotechnology ; Li Ka Shing Faculty of Medicine; The University of Hong Kong ; Hong Kong , China.|c Department of Medicine ; Li Ka Shing Faculty of Medicine; The University of Hong Kong ; Hong Kong , China.
Aimin
A
Xu
d Institute of Molecular and Cell Biology ; Biopolis A*STAR, Singapore.
Vinay
V
Tergaonkar
a Department of Pharmacology and Pharmacy and State Key Laboratory of Pharmaceutical Biotechnology ; Li Ka Shing Faculty of Medicine; The University of Hong Kong ; Hong Kong , China.
Paul M
PM
Vanhoutte
a Department of Pharmacology and Pharmacy and State Key Laboratory of Pharmaceutical Biotechnology ; Li Ka Shing Faculty of Medicine; The University of Hong Kong ; Hong Kong , China.|e School of Biomedical Sciences; Li Ka Shing Faculty of Medicine; The University of Hong Kong ; Hong Kong , China.
Eva Hoi Ching
EH
Tang
D000818:Animals; D001011:Aorta / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D005786:Gene Expression Regulation; D061307:Human Umbilical Vein Endothelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D051550:I-kappa B Kinase / Q000235:genetics / Q000378:metabolism; D020672:I-kappa B Proteins / Q000235:genetics / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D018345:Mice, Knockout; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000235:genetics* / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D058226:Plaque, Atherosclerotic / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D061251:Primary Cell Culture; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D000089804:Shelterin Complex; D015398:Signal Transduction; D034501:Telomere-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism
D020672:I-kappa B Proteins; D008070:Lipopolysaccharides; D016328:NF-kappa B; C000606204:NFKBIA protein, human; C000606205:Nfkbia protein, mouse; D034741:RNA, Small Interfering; D000089804:Shelterin Complex; C440809:TERF2IP protein, human; D034501:Telomere-Binding Proteins; D000072000:NF-KappaB Inhibitor alpha; D051550:I-kappa B Kinase; C496560:IKBKB protein, human
NFκB; atherosclerosis; macrophages; pro-inflammatory cytokines; repressor activator protein 1; signal transduction,; telomeric protein