ABSTRACT
Tumor necrosis factor (TNF)-related cytokines regulate cell death and survival and provide strong selective pressures for viruses, such as cytomegalovirus (CMV), to evolve counterstrategies in order to persist in immune-competent hosts. Signaling by the lymphotoxin (LT)-beta receptor or TNF receptor-1, but not Fas or TRAIL receptors, inhibits the cytopathicity and replication of human CMV by a nonapoptotic, reversible process that requires nuclear factor kappa B (NF-kappa B)-dependent induction of interferon-beta (IFN-beta). Efficient induction of IFN-beta requires virus infection and LT signaling, demonstrating the need for both host and viral factors in the curtailment of viral replication without cellular elimination. LT alpha-deficient mice and LT beta R-Fc transgenic mice were profoundly susceptible to murine CMV infection. Together, these results reveal an essential and conserved role for LTs in establishing host defense to CMV.
Subject(s)
Adaptor Proteins, Signal Transducing , Cytomegalovirus/physiology , Host-Parasite Interactions , Interferon-beta/biosynthesis , Lymphotoxin-alpha/pharmacology , Membrane Proteins/pharmacology , Transcriptional Activation , Tumor Necrosis Factor-alpha/pharmacology , Animals , Carrier Proteins/physiology , Cells, Cultured , Cytomegalovirus/growth & development , Cytomegalovirus/pathogenicity , Fas-Associated Death Domain Protein , Herpesviridae Infections/etiology , Humans , Interferon-beta/genetics , Interferon-beta/physiology , Lymphotoxin beta Receptor , Lymphotoxin-alpha/genetics , Mice , Mice, Transgenic , Muromegalovirus , NF-kappa B/physiology , Proteins/physiology , RNA, Messenger/biosynthesis , Receptors, Tumor Necrosis Factor/genetics , Survival Rate , TNF Receptor-Associated Factor 3 , Tumor Necrosis Factor Ligand Superfamily Member 14 , Virus Replication/drug effectsABSTRACT
Posttranslational phosphorylation of proteins is an important event in many cellular processes. Phosphorylated tyrosine residues can serve as association sites for other proteins in signal transduction cascades of tyrosine kinase receptors. Formation of phosphohistidine residues in proteins has been found in eukaryotic and prokaryotic organisms. Furthermore, it has been suggested that phosphohistidine might substitute for phosphotyrosine in conferring high-affinity binding to proteins involved in signal transduction. We have analyzed the ability of 3-phosphohistidine to associate with the known phosphotyrosine-specific phosphotyrosine binding and src homology 2 protein domains. From our binding studies using synthetic peptides, we conclude that 3-phosphohistidine cannot replace phosphotyrosine in conferring high-affinity binding to the phosphotyrosine binding domain of shc or the src homology 2 domain of phospholipase C-gamma1.
Subject(s)
Histidine/analogs & derivatives , Isoenzymes/metabolism , Peptides/metabolism , Phosphotyrosine/metabolism , Type C Phospholipases/metabolism , src Homology Domains , Amino Acid Sequence , Binding Sites , Binding, Competitive , Chromatography, High Pressure Liquid , Fluorescence Polarization , Histidine/metabolism , Isoenzymes/chemistry , Mass Spectrometry , Molecular Sequence Data , Peptides/chemical synthesis , Peptides/chemistry , Phospholipase C gamma , Phosphorylation , Protein Binding , Protein Processing, Post-Translational , Recombinant Fusion Proteins/immunology , Recombinant Fusion Proteins/metabolism , Signal Transduction , Type C Phospholipases/chemistryABSTRACT
Posttranslational phosphorylation of proteins is an important event in many cellular processes. Whereas phosphoesters of serine, threonine, and tyrosine have been studied extensively, only limited information is available for other amino acids modified by a phosphate group. The formation of phosphohistidine residues in proteins was discovered originally in prokaryotic organisms, but also has been found recently in eukaryotic cells. We describe methods for the synthesis and analysis of phosphohistidine-containing peptides, a prerequisite for the investigation of the role of this posttranslational modification in cellular processes.
Subject(s)
Histidine/analogs & derivatives , Phosphopeptides/chemical synthesis , Chromatography, High Pressure Liquid , Magnetic Resonance Spectroscopy , Protein Processing, Post-Translational , Spectrometry, Mass, Matrix-Assisted Laser Desorption-IonizationABSTRACT
A fibroblast growth factor receptor 1 variant missing 37 amino acids from the carboxy-terminal tyrosine kinase catalytic domain was discovered in human lung fibroblasts and several other human cell lines. The receptor variant binds specifically to acidic fibroblast growth factor but has no tyrosine kinase activity. It was found that cellular transfectants expressing the fibroblast growth factor receptor 1 variant are mitogenically inactive and ligand binding to the receptor causes neither receptor autophosphorylation nor phospholipase C-gamma transphosphorylation. The fibroblast growth factor receptor 1 variant therefore represents an inactive receptor for acidic fibroblast growth factor. Since both kinase and kinase-deficient receptor forms are expressed in cells, it is conceivable that the kinase-deficient receptor plays an important role in regulating cellular responses elicited by acidic fibroblast growth factor stimulation.
