title: Hsp70 inhibits lipopolysaccharide-induced NF-kappaB activation by interacting with TRAF6 and inhibiting its ubiquitination.
abstract: Inducible heat shock protein 70 (Hsp70) is one of the most important HSPs for maintenance of cell integrity during normal cellular growth as well as pathophysiological conditions. Tumor necrosis factor receptor-associated factor 6 (TRAF6) is a crucial signaling transducer that regulates a diverse array of physiological and pathological processes and is essential for activating NF-kappaB signaling pathway in response to bacterial lipopolysaccharide (LPS). Here we report a novel mechanism of Hsp70 for preventing LPS-induced NF-kappaB activation in RAW264.7 macrophage-like cells. Our results show that Hsp70 can associate with TRAF6 physically in the TRAF-C domain and prevent TRAF6 ubiquitination. The stimulation of LPS dissociates the binding of Hsp70 and TRAF6 in a time-dependent manner. Hsp70 inhibits LPS-induced NF-kappaB signaling cascade activation in heat-shock treated as well as Hsp70 stable transfected RAW264.7 cells and subsequently decreases iNOS and COX-2 expression. Two Hsp70 mutants, Hsp70DeltaC(1-428aa) with N-terminal ATPase domain and Hsp70C(428-642aa) with C-terminal domain, lack the ability to influence TRAF6 ubiquitination and TRAF6-triggered NF-kappaB activation. Taken together, these findings indicate that Hsp70 inhibits LPS-induced NF-kappaB activation by binding TRAF6 and preventing its ubiquitination, and results in inhibition of inflammatory mediator production, which provides a new insight for analyzing the effects of Hsp70 on LPS-triggered inflammatory signal transduction pathways.
authors.affiliation: Jiangsu Province Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, 122 Ninghai Road, Nanjing 210097, Jiangsu Province, PR China.
authors.forename: Huaqun
authors.initials: H
authors.lastname: Chen
authors.forename: Yifan
authors.initials: Y
authors.lastname: Wu
authors.forename: Yiqing
authors.initials: Y
authors.lastname: Zhang
authors.forename: Lina
authors.initials: L
authors.lastname: Jin
authors.forename: Lan
authors.initials: L
authors.lastname: Luo
authors.forename: Bin
authors.initials: B
authors.lastname: Xue
authors.forename: Chen
authors.initials: C
authors.lastname: Lu
authors.forename: Xiran
authors.initials: X
authors.lastname: Zhang
authors.forename: Zhimin
authors.initials: Z
authors.lastname: Yin
mesh_terms: D000818:Animals; D051546:Cyclooxygenase 2 / Q000378:metabolism; D015536:Down-Regulation; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary / Q000235:genetics; D048029:TNF Receptor-Associated Factor 6 / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism*
chemical_list: D018840:HSP70 Heat-Shock Proteins; D008070:Lipopolysaccharides; D016328:NF-kappa B; D048029:TNF Receptor-Associated Factor 6; D025801:Ubiquitin; D052247:Nitric Oxide Synthase Type II; D051546:Cyclooxygenase 2