Integrin β1 mediates vaccinia virus entry through activation of PI3K/Akt signaling.
ABSTRACT Vaccinia virus has a broad range of infectivity in many cell lines and animals. Although it is known that the vaccinia mature virus binds to cell surface glycosaminoglycans and extracellular matrix proteins, whether additional cellular receptors are required for virus entry remains unclear. Our previous studies showed that the vaccinia mature virus enters through lipid rafts, suggesting the involvement of raft-associated cellular proteins. Here we demonstrate that one lipid raft-associated protein, integrin β1, is important for vaccinia mature virus entry into HeLa cells. Vaccinia virus associates with integrin β1 in lipid rafts on the cell surface, and the knockdown of integrin β1 in HeLa cells reduces vaccinia mature virus entry. Additionally, vaccinia mature virus infection is reduced in a mouse cell line, GD25, that is deficient in integrin β1 expression. Vaccinia mature virus infection triggers the activation of phosphatidylinositol 3-kinase (PI3K)/Akt signaling, and the treatment of cells with inhibitors to block P13K activation reduces virus entry in an integrin β1-dependent manner, suggesting that integrin β1-mediates PI3K/Akt activation induced by vaccinia virus and that this signaling pathway is essential for virus endocytosis. The inhibition of integrin β1-mediated cell adhesion results in a reduction of vaccinia virus entry and the disruption of focal adhesion and PI3K/Akt activation. In summary, our results show that the binding of vaccinia mature virus to cells mimics the outside-in activation process of integrin functions to facilitate vaccinia virus entry into HeLa cells.
Article: beta1-integrin-mediated signaling essentially contributes to cell survival after radiation-induced genotoxic injury.[show abstract] [hide abstract]
ABSTRACT: Integrin-mediated adhesion to extracellular matrix proteins confers resistance to radiation- or drug-induced genotoxic injury. To analyse the underlying mechanisms specific for beta1-integrins, wild-type beta1A-integrin-expressing GD25beta1A cells were compared to GD25beta1B cells, which express signaling-incompetent beta1B variants. Cells grown on fibronectin, collagen-III, beta1-integrin-IgG or poly-l-lysine were exposed to 0-6 Gy X-rays in presence or depletion of growth factors and phosphatidylinositol-3 kinase (PI3K) inhibitors (LY294002, wortmannin). In order to test the relevance of these findings in tumor cells, human A-172 glioma cells were examined under the same conditions after siRNA-mediated silencing of beta1-integrins. We found that beta1A-integrin-mediated adhesion to fibronectin, collagen-III or beta1-IgG was essential for cell survival after radiation-induced genotoxic injury. Mediated by PI3K, pro-survival beta1A-integrin/Akt signaling was critically involved in this process. Additionally, the beta1-integrin downstream targets p130Cas and paxillin-impaired survival-regulating PI3K-dependent JNK. In A-172 glioma cells, beta1-integrin knockdown and PI3K inhibition confirmed the central role of beta1-integrins in Akt- and p130Cas/paxillin-mediated prosurvival signaling. These findings suggest beta1-integrins as critical regulators of cell survival after radiation-induced genotoxic injury. Elucidation of the molecular circuitry of prosurvival beta1-integrin-mediated signaling in tumor cells may promote the development of innovative molecular-targeted therapeutic antitumor strategies.Oncogene 04/2006; 25(9):1378-90. · 6.37 Impact Factor
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ABSTRACT: The monoclonal antibody 2D5 neutralized vaccinia virus by preventing penetration of the virus and reacting with VP23-29K. The conformation of the VP23-29K was maintained by a disulfide bond(s), and the 2D5mAb reacted stronger with the nonreduced 23-kDa form than with the reduced 29-kDa form. We selected several escape mutants. Sequences of the A17L genes, which were thought to encode the VP23-29K, did not show cognate mutation. Genomic DNA of a 2D5mAb-resistant mutant (M4) was cleaved with HindIII, and all the fragments were introduced into parental IHD-J strain vaccinia virus by transfection. Only the L fragment produced a 2D5mAb-resistant virus. Dissection of the L fragment and subsequent transfection revealed that the L1R gene induced the 2D5mAb-resistant virus. The 2D5mAb-resistant mutants showed a consensus G to A conversion at nucleotide 101 of their LIRs which would replace asparatic acid 35 with asparagine. Ishibashi-111 strain mousepox virus spontaneously resistant to 2D5mAb also had the same sequence at this region. Moreover, the VP23-29K was myristoylated as predicted by the L1R gene. The coding gene of the VP23-29K was L1R.Virology 07/1996; 220(2):491-4. · 3.35 Impact Factor
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ABSTRACT: The protein content of vaccinia virus mature virions, purified by rate zonal and isopycnic centrifugations and solubilized by SDS or a solution of urea and thiourea, was determined by the accurate mass and time tag technology which uses both tandem mass spectrometry and Fourier transform-ion cyclotron resonance mass spectrometry to detect tryptic peptides separated by high-resolution liquid chromatography. Eighty vaccinia virus-encoded proteins representing 37% of the 218 genes annotated in the complete genome sequence were detected in at least three analyses. Ten proteins accounted for approximately 80% of the virion mass. Thirteen identified proteins were not previously reported as components of virions. On the other hand, 8 previously described virion proteins were not detected here, presumably due to technical reasons including small size and hydrophobicity. In addition to vaccinia virus-encoded proteins, 24 host proteins omitting isoforms were detected. The most abundant of these were cytoskeletal proteins, heat shock proteins and proteins involved in translation.Virology 03/2007; 358(1):233-47. · 3.35 Impact Factor