Src signaling involvement in Japanese encephalitis virus-induced cytokine production in microglia

• Published in: Neurochemistry international 2011-07, Vol.58 (8), p.924-933
• Main Authors: Chen, Chun-Jung, Ou, Yen-Chuan, Chang, Cheng-Yi, Pan, Hung-Chuan, Lin, Shih-Yi, Liao, Su-Lan, Raung, Shue-Ling, Chen, Shih-Yun, Chang, Chen-Jung
• Format: Article
• Language: English
• Subjects: Animals; Animals, Newborn; Biological and medical sciences; Cells, Cultured; Culicidae; Cytokine; Cytokines - biosynthesis; Encephalitis Virus, Japanese - isolation & purification; Fundamental and applied biological sciences. Psychology; Interleukin-1beta - biosynthesis; Japanese encephalitis virus; Lipid raft; Membrane Microdomains - physiology; Microglia; Microglia - enzymology; Microglia - metabolism; Microglia - virology; Rats; Rats, Sprague-Dawley; Signal Transduction - physiology; Src; src-Family Kinases - metabolism; src-Family Kinases - physiology; Tumor Necrosis Factor-alpha - biosynthesis; Vertebrates: nervous system and sense organs
• ISSN: 0197-0186; 1872-9754
• DOI: 10.1016/j.neuint.2011.02.022

► JEV infection triggers microglia releasing of TNF-α and IL-1β. ► JEV infection initiates Src/Ras/Raf/ERK/NF-κB signaling in microglia. ► JEV infection initiates Src/Raf/ERK/NF-κB signaling in microglia. ► The disruption of lipid rafts attenuates JEV-initiated Src-related signaling and TNF-α/IL-1β expression in microglia. Numerous studies have demonstrated that the disease pathogenesis of Japanese encephalitis involves cytokine-mediated bystander damage. The mechanisms involved in the regulation of Japanese encephalitis virus (JEV)-induced cytokine expression are not well defined but rely mainly on the tight regulation of transcription factor NF-κB. The Src-family tyrosine kinases participate in diversity of cellular signaling and have been demonstrated in JEV-infected cells. A direct link leading from Src activation to NF-κB activation in JEV-induced cytokine expression is incompletely understood. Here, we report that Src-related Ras/Raf/extracellular signal-regulated kinase (ERK) cascades participate in NF-κB activation and consequent tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β) expression in JEV-infected microglia. Central microglia were capable of producing TNF-α and IL-1β after JEV infection. However, JEV infection had a negligible effect on triggering TNF-α and IL-1β production by neurons and astrocytes. The expression of TNF-α and IL-1β caused by JEV was accompanied by increased Src phosphorylation, Ras membrane association, Raf serine-338 as well as tyrosine-340 phosphorylation, ERK phosphorylation, NF-κB DNA binding activity, and decreased Raf serine-259 phosphorylation. Pharmacological studies revealed that the integrity of lipid raft and the activation of Src, Ras, Raf, ERK, and NF-κB all contributed to JEV-induced TNF-α and IL-1β expression. Pharmacological and biochemical studies further suggested that Src, upon activation, might transmit signals to the Raf/ERK cascades via Ras-dependent and -independent mechanisms that in turn might lead to NF-κB activation. Overall, our results show that the lipid raft might play a role in mediating JEV-initiated Src/Ras/Raf/ERK/NF-κB signaling and TNF-α/IL-1β expression in microglia.