The Fas/CD95 surface receptor mediates rapid death of various cell types, including autoreactive T cells with the potential for triggering autoimmunity. Here, we present novel aspects of Fas signalling that define a ...The Fas/CD95 surface receptor mediates rapid death of various cell types, including autoreactive T cells with the potential for triggering autoimmunity. Here, we present novel aspects of Fas signalling that define a ＇social＇ dimension to receptor-induced apoptosis. Fas stimulation rapidly induces extensive membrane nanotube formation between neighbouring T cells. This is critically dependent on Rho GTPases but not on caspase activation. Bidirectional transfer of membrane and cytosolic elements including active caspases can be observed to occur via these nanotubes. Nanotube formation and intercellular exchanges of death signals are defective in T lymphocytes from patients with autoimmune iymphoproliferative syndrome harbouring mutations in the Fas receptor. We conclude that nanotuhemediated exchanges constitute a novel form of intercellular communication that augments the propagation of death signalling between neighbouring T cells.展开更多
BACKGROUND Aminoacyl tRNA synthetases/ligases(ARSs)are highly conserved enzymes involved in attaching amino acids to tRNA promoting protein synthesis.Although deficiencies of ARSs localized to the mitochondria classic...BACKGROUND Aminoacyl tRNA synthetases/ligases(ARSs)are highly conserved enzymes involved in attaching amino acids to tRNA promoting protein synthesis.Although deficiencies of ARSs localized to the mitochondria classically present with neuropathology,the clinical features of cytosolic ARS deficiencies are more variable.They have previously been associated with neonatal hepatitis,but never with early-onset inflammatory bowel disease.CASE SUMMARY A nine-year-old Bangladeshi boy presented with neonatal liver failure and deranged clotting,transaminitis and cholestasis.His parents were first cousins.Two older brothers and a sister were well.The patient suffered from loose stools from early infancy which became more troublesome and persistent from five years old with ten bloody motions a day.Repeated endoscopies showed persistent pancolitis,which was refractory to mesalazine,corticosteroids,azathioprine,sirolimus and anti-TNF(adalimumab)therapy,but has improved recently with subcutaneous methotrexate.Whole Genome Sequencing revealed a novel pathogenic missense variant(c.290A>G)in the cytosolic isoleucyl-tRNA synthetase gene,leading to an amino acid substitution(p.Asp97Gly).Pathogenic variants in other genes associated with inflammatory bowel disease(IBD)(ADAM17,EGFR,FOXP3,IL10RA,IL10RB,IL21R,NCF4,STAT3)were excluded.Cytokine assays demonstrated markedly elevated IL-2,IL-5,IL-13,IL-9 and IL-10 by the patient’s CD4+T-cells,while IL-17A,IL-17F,IFNβwere lower,and TNFαnot significantly different when compared to healthy controls.CONCLUSION This case report provides evidence that recessive mutations in cytosolic isoleucyltRNA synthetase are a novel monogenic cause of IBD,which should be considered,particularly in infants and children with a history of neonatal hepatitis and very early-onset IBD poorly responsive to treatment.展开更多
文摘The Fas/CD95 surface receptor mediates rapid death of various cell types, including autoreactive T cells with the potential for triggering autoimmunity. Here, we present novel aspects of Fas signalling that define a ＇social＇ dimension to receptor-induced apoptosis. Fas stimulation rapidly induces extensive membrane nanotube formation between neighbouring T cells. This is critically dependent on Rho GTPases but not on caspase activation. Bidirectional transfer of membrane and cytosolic elements including active caspases can be observed to occur via these nanotubes. Nanotube formation and intercellular exchanges of death signals are defective in T lymphocytes from patients with autoimmune iymphoproliferative syndrome harbouring mutations in the Fas receptor. We conclude that nanotuhemediated exchanges constitute a novel form of intercellular communication that augments the propagation of death signalling between neighbouring T cells.
文摘BACKGROUND Aminoacyl tRNA synthetases/ligases(ARSs)are highly conserved enzymes involved in attaching amino acids to tRNA promoting protein synthesis.Although deficiencies of ARSs localized to the mitochondria classically present with neuropathology,the clinical features of cytosolic ARS deficiencies are more variable.They have previously been associated with neonatal hepatitis,but never with early-onset inflammatory bowel disease.CASE SUMMARY A nine-year-old Bangladeshi boy presented with neonatal liver failure and deranged clotting,transaminitis and cholestasis.His parents were first cousins.Two older brothers and a sister were well.The patient suffered from loose stools from early infancy which became more troublesome and persistent from five years old with ten bloody motions a day.Repeated endoscopies showed persistent pancolitis,which was refractory to mesalazine,corticosteroids,azathioprine,sirolimus and anti-TNF(adalimumab)therapy,but has improved recently with subcutaneous methotrexate.Whole Genome Sequencing revealed a novel pathogenic missense variant(c.290A>G)in the cytosolic isoleucyl-tRNA synthetase gene,leading to an amino acid substitution(p.Asp97Gly).Pathogenic variants in other genes associated with inflammatory bowel disease(IBD)(ADAM17,EGFR,FOXP3,IL10RA,IL10RB,IL21R,NCF4,STAT3)were excluded.Cytokine assays demonstrated markedly elevated IL-2,IL-5,IL-13,IL-9 and IL-10 by the patient’s CD4+T-cells,while IL-17A,IL-17F,IFNβwere lower,and TNFαnot significantly different when compared to healthy controls.CONCLUSION This case report provides evidence that recessive mutations in cytosolic isoleucyltRNA synthetase are a novel monogenic cause of IBD,which should be considered,particularly in infants and children with a history of neonatal hepatitis and very early-onset IBD poorly responsive to treatment.
