Intracellular RNA viruses are sensed by receptors retinoic acid-inducible gene 1 （RIG-I）/melanoma differentiation-associated gene 5 （MDA5） that trigger the formation of MAVS signal complex on mitochondria. Consequ...Intracellular RNA viruses are sensed by receptors retinoic acid-inducible gene 1 （RIG-I）/melanoma differentiation-associated gene 5 （MDA5） that trigger the formation of MAVS signal complex on mitochondria. Consequently, this leads to the activation of TANK-binding kinase 1 （TBK1） and phosphorylation of interferon regulatory factor 3 （IRF3）, both of which constitutively associate with cytosolic chaperone Hsp90. It remains largely unknown how MAVS activates TBK1/IRF3. In this study, we identified translocases of outer membrane 70 （Tom70）, a mitochondrial import receptor, to interact with MAVS upon RNA virus infection. Ectopic expression or knockdown of Tom70 could enhance or impair IRF3-mediated gene expression, respectively. Mechanistically, the clamp domain （R192） of Tom70 interacts with the C-terminal motif （EEVD） of Hsp90, thus recruiting TBK1/IRF3 to mitochondria. Disruption of this interaction or mislocation of Tom70 sharply impairs activation of TBK1 and IRF3. Furthermore, host antiviral responses are significantly boosted or crippled in the presence or absence of Tom70. Collectively, our study characterizes Tom70 as a critical adaptor linking MAVS to TBK1/IRF3, revealing that mitochondrion is evolutionarily integrated with innate immunity.展开更多
Mesenchymal stem cell （MSC） transplantation has shown a therapeutic potential to repair the ischemic and infracted myocardium, but the effects are limited by the apoptosis and loss of donor cells in host cardiac mic...Mesenchymal stem cell （MSC） transplantation has shown a therapeutic potential to repair the ischemic and infracted myocardium, but the effects are limited by the apoptosis and loss of donor cells in host cardiac microenvironment. The aim of this study is to explore the cytoprotection of heat shock protein 90 （Hsp90） against hypoxia and serum deprivation-induced apoptosis and the possible mechanisms in rat MSCs. Cell viability was determined by 3-（4,5-dimethylthiazol-2-yl）-2,5-diphenyltetrazolium bromide （MTT） assay. Apoptosis was assessed by Hoechst 33258 nuclear staining and flow cytometric analysis with annexin V/PI staining. The gene expression of Toll-like receptor-4 （TLR-4） and V-erb-b2 erythroblastic leukemia viral oncogene homolog 2 （ErbB2） was detected by real-time poly- merase chain reaction （PCR）. The protein levels of cleaved caspase-3, Bcl-2, Bcl-xL, Bax, totaI-ERK, phospho-ERK, totaI-Akt, phospho-Akt, and Hsp90 were detected by Western blot. The production of nitric oxide was measured by spectrophotometric assay. Hsp90 improves MSC viability and protects MSCs against apoptosis induced by serum deprivation and hypoxia. The protective role of Hsp90 not only elevates Bcl-2/Bax and Bcl-xL/Bax expression and attenuates cleaved caspase-3 expression via down-regulating membrane TLR-4 and ErbB2 receptors and then ac- tivating their downstream PI3K/Akt and ERK1/2 pathways, but also enhances the paracrine effect of MSCs. These findings demonstrated a novel and effective treatment strategy against MSC apoptosis in cell transplantation.展开更多
文摘Intracellular RNA viruses are sensed by receptors retinoic acid-inducible gene 1 （RIG-I）/melanoma differentiation-associated gene 5 （MDA5） that trigger the formation of MAVS signal complex on mitochondria. Consequently, this leads to the activation of TANK-binding kinase 1 （TBK1） and phosphorylation of interferon regulatory factor 3 （IRF3）, both of which constitutively associate with cytosolic chaperone Hsp90. It remains largely unknown how MAVS activates TBK1/IRF3. In this study, we identified translocases of outer membrane 70 （Tom70）, a mitochondrial import receptor, to interact with MAVS upon RNA virus infection. Ectopic expression or knockdown of Tom70 could enhance or impair IRF3-mediated gene expression, respectively. Mechanistically, the clamp domain （R192） of Tom70 interacts with the C-terminal motif （EEVD） of Hsp90, thus recruiting TBK1/IRF3 to mitochondria. Disruption of this interaction or mislocation of Tom70 sharply impairs activation of TBK1 and IRF3. Furthermore, host antiviral responses are significantly boosted or crippled in the presence or absence of Tom70. Collectively, our study characterizes Tom70 as a critical adaptor linking MAVS to TBK1/IRF3, revealing that mitochondrion is evolutionarily integrated with innate immunity.
基金Project supported by the National Natural Science Foundation of China (Nos.30670868,30770887,and 30770887/H0220)the Key Lab of Traditional Chinese Medicine of Zhejiang Province (No.ZK23812)the Qianjiang Talent Scheme Foundation of Zhejiang Province (No.2009R10069),China
文摘Mesenchymal stem cell （MSC） transplantation has shown a therapeutic potential to repair the ischemic and infracted myocardium, but the effects are limited by the apoptosis and loss of donor cells in host cardiac microenvironment. The aim of this study is to explore the cytoprotection of heat shock protein 90 （Hsp90） against hypoxia and serum deprivation-induced apoptosis and the possible mechanisms in rat MSCs. Cell viability was determined by 3-（4,5-dimethylthiazol-2-yl）-2,5-diphenyltetrazolium bromide （MTT） assay. Apoptosis was assessed by Hoechst 33258 nuclear staining and flow cytometric analysis with annexin V/PI staining. The gene expression of Toll-like receptor-4 （TLR-4） and V-erb-b2 erythroblastic leukemia viral oncogene homolog 2 （ErbB2） was detected by real-time poly- merase chain reaction （PCR）. The protein levels of cleaved caspase-3, Bcl-2, Bcl-xL, Bax, totaI-ERK, phospho-ERK, totaI-Akt, phospho-Akt, and Hsp90 were detected by Western blot. The production of nitric oxide was measured by spectrophotometric assay. Hsp90 improves MSC viability and protects MSCs against apoptosis induced by serum deprivation and hypoxia. The protective role of Hsp90 not only elevates Bcl-2/Bax and Bcl-xL/Bax expression and attenuates cleaved caspase-3 expression via down-regulating membrane TLR-4 and ErbB2 receptors and then ac- tivating their downstream PI3K/Akt and ERK1/2 pathways, but also enhances the paracrine effect of MSCs. These findings demonstrated a novel and effective treatment strategy against MSC apoptosis in cell transplantation.
