Host resistance to viral infection requires type I (α/β) and II (γ) interferon (IFN) production. Another important defense mechanism is the degradative activity of macroautophagy (herein autophagy), ...mediated by the coordinated action of evolutionarily conserved autophagy proteins (Atg). We show that the Atg5-Atg12/Atg16L1 protein complex, whose prior known function is in autophagosome formation, is required for IFNγ-mediated host defense against murine norovirus (MNV) infection. Importantly, the direct antiviral activity of IFNγ against MNV in macrophages required Atg5-Atg12, Atg7, and Atg16L1, but not induction of autophagy, the degradative activity of lysosomal proteases, fusion of autophagosomes and lysosomes, or the Atg8-processing protein Atg4B. IFNγ, via Atg5-Atg12/Atg16L1, inhibited formation of the membranous cytoplasmic MNV replication complex, where Atg16L1 localized. Thus, the Atg5-Atg12/Atg16L1 complex performs a pivotal, nondegradative role in IFNγ-mediated antiviral defense, establishing that multicellular organisms have evolved to use portions of the autophagy pathway machinery in a cassette-like fashion for host defense.
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► Atg5-Atg12/Atg16L1 and Atg7 are required for IFNγ to inhibit norovirus replication ► The degradative activity of autophagy is not required for the antiviral activity of IFNγ ► IFNγ, via autophagy proteins, inhibits the formation of the replication complex
Autophagy regulates cell differentiation, proliferation, and survival in multiple cell types, including cells of the immune system. In this study, we examined the effects of a disruption of autophagy ...on the differentiation of invariant NKT (iNKT) cells. Using mice with a T lymphocyte-specific deletion of Atg5 or Atg7, two members of the macroautophagic pathway, we observed a profound decrease in the iNKT cell population. The deficit is cell-autonomous, and it acts predominantly to reduce the number of mature cells, as well as the function of peripheral iNKT cells. In the absence of autophagy, there is reduced progression of iNKT cells in the thymus through the cell cycle, as well as increased apoptosis of these cells. Importantly, the reduction in Th1-biased iNKT cells is most pronounced, leading to a selective reduction in iNKT cell-derived IFN-γ. Our findings highlight the unique metabolic and genetic requirements for the differentiation of iNKT cells.
The importance of autophagy in the generation of memory CD8(+) T cells in vivo is not well defined. We report here that autophagy was dynamically regulated in virus-specific CD8(+) T cells during ...acute infection of mice with lymphocytic choriomeningitis virus. In contrast to the current paradigm, autophagy decreased in activated proliferating effector CD8(+) T cells and was then upregulated when the cells stopped dividing just before the contraction phase. Consistent with those findings, deletion of the gene encoding either of the autophagy-related molecules Atg5 or Atg7 had little to no effect on the proliferation and function of effector cells, but these autophagy-deficient effector cells had survival defects that resulted in compromised formation of memory T cells. Our studies define when autophagy is needed during effector and memory differentiation and warrant reexamination of the relationship between T cell activation and autophagy.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The bone morphogenetic protein (BMP) family, the largest subfamily of the structurally conserved transforming growth factor-β (TGF-β) superfamily of growth factors, are multifunctional regulators of ...development, proliferation, and differentiation. The TGF-β type III receptor (TβRIII or betaglycan) is an abundant cell surface proteoglycan that has been well characterized as a TGF-β and inhibin receptor. Here we demonstrate that TβRIII functions as a BMP cell surface receptor. TβRIII directly and specifically binds to multiple members of the BMP subfamily, including BMP-2, BMP-4, BMP-7, and GDF-5, with similar kinetics and ligand binding domains as previously identified for TGF-β. TβRIII also enhances ligand binding to the BMP type I receptors, whereas short hairpin RNA-mediated silencing of endogenous TβRIII attenuates BMP-mediated Smad1 phosphorylation. Using a biologically relevant model for TβRIII function, we demonstrate that BMP-2 specifically stimulates TβRIII-mediated epithelial to mesenchymal cell transformation. The ability of TβRIII to serve as a cell surface receptor and mediate BMP, inhibin, and TGF-β signaling suggests a broader role for TβRIII in orchestrating TGF-β superfamily signaling.
Transforming growth factor β (TGFβ) has an important role as a negative regulator of cellular proliferation. The type III transforming growth factor β receptor (TβRIII) has an emerging role as both a ...TGFβ superfamily co-receptor and in mediating signaling through its cytoplasmic domain. In L6 myoblasts, TβRIII expression enhanced TGFβ1-mediated growth inhibition, with this effect mediated, in part, by the TβRIII cytoplasmic domain. The effects of TβRIII were not due to altered ligand presentation or to differences in Smad2 phosphorylation. Instead, TβRIII specifically increased Smad3 phosphorylation, both basal and TGFβ-stimulated Smad3 nuclear localization and Smad3-dependent activation of reporter genes independent of its cytoplasmic domain. Conversely, SB431542, a type I transforming growth factor β receptor (TβRI) inhibitor, as well as dominant-negative Smad3 specifically and significantly abrogated the effects of TβRIII on TGFβ1-mediated inhibition of proliferation. TβRIII also specifically increased p38 phosphorylation, and SB203580, a p38 kinase inhibitor, specifically and significantly abrogated the effects of TβRIII/TGFβ1-mediated inhibition of proliferation in L6 myoblasts and in primary human epithelial cells. Importantly, treatment with the TβRI and p38 inhibitors together had additive effects on abrogating TβRIII/TGFβ1-mediated inhibition of proliferation. In a reciprocal manner, short hairpin RNA-mediated knockdown of endogenous TβRIII in various human epithelial cells attenuated TGFβ1-mediated inhibition of proliferation. Taken together, these data demonstrate that TβRIII contributes to and enhances TGFβ-mediated growth inhibition through both TβRI/Smad3-dependent and p38 mitogen-activated protein kinase pathways.
We used a genetic screen based on tRNA-mediated suppression (TMS) in a Schizosaccharomyces pombe La protein (Sla1p) mutant. Suppressor pre-tRNASerUCA-C47:6U with a debilitating substitution in its ...variable arm fails to produce tRNA in a sla1-rrm mutant deficient for RNA chaperone-like activity. The parent strain and spontaneous mutant were analyzed using Solexa sequencing. One synonymous single-nucleotide polymorphism (SNP), unrelated to the phenotype, was identified. Further sequence analyses found a duplication of the tRNASerUCA-C47:6U gene, which was shown to cause the phenotype. Ninety percent of 28 isolated mutants contain duplicated tRNASerUCA-C47:6U genes. The tRNA gene duplication led to a disproportionately large increase in tRNASerUCA-C47:6U levels in sla1-rrm but not sla1-null cells, consistent with non-specific low-affinity interactions contributing to the RNA chaperone-like activity of La, similar to other RNA chaperones. Our analysis also identified 24 SNPs between ours and S. pombe 972h- strain yFS101 that was recently sequenced using Solexa. By including mitochondrial (mt) DNA in our analysis, overall coverage increased from 52% to 96%. mtDNA from our strain and yFS101 shared 14 mtSNPs relative to a 'reference' mtDNA, providing the first identification of these S. pombe mtDNA discrepancies. Thus, strain-specific and spontaneous phenotypic mutations can be mapped in S. pombe by Solexa sequencing.
Autophagy regulates cell differentiation, proliferation and survival in multiple cell types, including cells of the immune system. Herein we examined the effects of a disruption of autophagy on the ...differentiation of invariant natural killer T cells (
i
NKT cells). Using mice with a T lymphocyte specific deletion of
Atg5
or
Atg7
,two members of the macroautophagic pathway, we observed a profound decrease in the
i
NKT cell population. The deficit is cell-autonomous, and it acts predominantly to reduce the number of mature cells, as well as the function of peripheral
i
NKT cells. In the absence of autophagy, there is reduced progression of
i
NKT cells in the thymus through the cell cycle, as well as increased apoptosis of these cells. Importantly, the reduction in Th1-biased
i
NKT cells is most pronounced, leading to a selective reduction in
i
NKT cell derived IFNγ. Our findings highlight the unique metabolic and genetic requirements for the differentiation of
i
NKT cells.
The importance of autophagy in the generation of memory CD8 super(+) T cells in vivo is not well defined. We report here that autophagy was dynamically regulated in virus-specific CD8 super(+) T ...cells during acute infection of mice with lymphocytic choriomeningitis virus. In contrast to the current paradigm, autophagy decreased in activated proliferating effector CD8 super(+) T cells and was then upregulated when the cells stopped dividing just before the contraction phase. Consistent with those findings, deletion of the gene encoding either of the autophagy-related molecules Atg5 or Atg7 had little to no effect on the proliferation and function of effector cells, but these autophagy-deficient effector cells had survival defects that resulted in compromised formation of memory T cells. Our studies define when autophagy is needed during effector and memory differentiation and warrant reexamination of the relationship between T cell activation and autophagy.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The importance of autophagy in the generation of memory CD8.sup.+T cells in vivo is not well defined. We report here that autophagy was dynamically regulated in virus-specific CD8.sup.+T cells during ...acute infection of mice with lymphocytic choriomeningitis virus. In contrast to the current paradigm, autophagy decreased in activated proliferating effector CD8.sup.+T cells and was then upregulated when the cells stopped dividing just before the contraction phase. Consistent with those findings, deletion of the gene encoding either of the autophagy-related molecules Atg5 or Atg7 had little to no effect on the proliferation and function of effector cells, but these autophagy-deficient effector cells had survival defects that resulted in compromised formation of memory T cells. Our studies define when autophagy is needed during effector and memory differentiation and warrant reexamination of the relationship between T cell activation and autophagy.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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