Subject(s)
Carrier Proteins/physiology , Cytokines/antagonists & inhibitors , Cytokines/physiology , DNA-Binding Proteins , Down-Regulation/immunology , Intracellular Signaling Peptides and Proteins , Proteins/physiology , Repressor Proteins , Signal Transduction/immunology , Trans-Activators , Transcription Factors , Animals , Carrier Proteins/genetics , Cytokines/genetics , Down-Regulation/genetics , Humans , Intracellular Fluid/immunology , Intracellular Fluid/physiology , Multigene Family/immunology , Proteins/genetics , Signal Transduction/genetics , Suppressor of Cytokine Signaling 1 Protein , Suppressor of Cytokine Signaling 3 Protein , Suppressor of Cytokine Signaling ProteinsABSTRACT
IL-4 is an important regulator of the activation, proliferation, and differentiation of many hematopoetic cells. Many of these biological effects result from the activation of Janus kinases (JAK)1 and JAK3 and the transcription factor Stat6. Recent data suggest that members of the SOCS (suppressor of cytokine signaling) family of proteins can inhibit JAK-STAT signaling. We have examined the ability of SOCS family members to suppress IL-4 signaling, and we have found that SOCS-1 potently inhibits the activation of JAK1 kinase and Stat6 in response to IL-4. Furthermore, SOCS-1 can inhibit the induction of CD23 expression by IL-4. SOCS-2 does not inhibit induction of signaling by IL-4, while inhibition of IL-4 signaling by SOCS-3 can be detected in transient transfection systems, but not in stable cell lines. These studies implicate SOCS-1 in modulation of IL-4 signaling and suggest that SOCS-1 may play a role in regulating the immune response.
Subject(s)
Carrier Proteins/physiology , DNA-Binding Proteins , Enzyme Inhibitors/pharmacology , Interleukin-4/antagonists & inhibitors , Interleukin-4/physiology , Intracellular Signaling Peptides and Proteins , Repressor Proteins , Signal Transduction/immunology , Transcription Factors , Carrier Proteins/genetics , Cell Line , Humans , Immunosuppressive Agents/pharmacology , Janus Kinase 1 , Janus Kinase 3 , Protein-Tyrosine Kinases/antagonists & inhibitors , Proteins/genetics , Proteins/physiology , STAT6 Transcription Factor , Signal Transduction/drug effects , Suppressor of Cytokine Signaling 1 Protein , Suppressor of Cytokine Signaling 3 Protein , Suppressor of Cytokine Signaling Proteins , Trans-Activators/metabolism , Transcription, Genetic/drug effects , Transcription, Genetic/immunology , TransfectionABSTRACT
In Abelson murine leukemia virus (A-MuLV)-transformed cells, members of the Janus kinase (Jak) family of non-receptor tyrosine kinases and the signal transducers and activators of transcription (STAT) family of signaling proteins are constitutively activated. In these cells, the v-Abl oncoprotein and the Jak proteins physically associate. To define the molecular mechanism of constitutive Jak-STAT signaling in these cells, the functional significance of the v-Abl-Jak association was examined. Mapping the Jak1 interaction domain in v-Abl demonstrates that amino acids 858 to 1080 within the carboxyl-terminal region of v-Abl bind Jak1 through a direct interaction. A mutant of v-Abl lacking this region exhibits a significant defect in Jak1 binding in vivo, fails to activate Jak1 and STAT proteins, and does not support either the proliferation or the survival of BAF/3 cells in the absence of cytokine. Cells expressing this v-Abl mutant show extended latency and decreased frequency in generating tumors in nude mice. In addition, inducible expression of a kinase-inactive mutant of Jak1 protein inhibits the ability of v-Abl to activate STATs and to induce cytokine-independent proliferation, indicating that an active Jak1 is required for these v-Abl-induced signaling pathways in vivo. We propose that Jak1 is a mediator of v-Abl-induced STAT activation and v-Abl induced proliferation in BAF/3 cells, and may be important for efficient transformation of immature B cells by the v-abl oncogene.
Subject(s)
Cell Division/physiology , Interleukin-3/physiology , Oncogene Proteins v-abl/chemistry , Protein-Tyrosine Kinases/metabolism , Animals , Binding Sites/physiology , Cell Line , Gene Expression Regulation/genetics , Janus Kinase 1 , Mice , Mice, Nude , Neoplasms, Experimental , Protein Binding , Signal Transduction/physiology , Transcriptional Activation/physiology , Transfection/geneticsABSTRACT
OBJECTIVE: To characterize the binding properties and variable-region sequences of LG4-1, a monoclonal antibody from an autoimmune MRL/Mp-lpr/lpr mouse that reacts specifically with nucleosome core particles and represents a new antinuclear antibody specificity. METHODS: The reactivity of the antibody against various nuclear substrates was determined using an enzymatic immunoassay, and the variable-region genes were sequenced from messenger RNA, using the dideoxy chain termination method. RESULTS: LG4-1 was found to react with nucleosome core particles but not with individual histones and DNA, or with various histone-histone and histone-DNA complexes. It was demonstrated that this antibody is encoded by a combination of variable-region genes and gene segments that have undergone few somatic mutations. CONCLUSION: The nucleosome core particle expresses a unique conformational autoepitope(s) resulting from the ordered association of histones and DNA.
Subject(s)
Antibodies, Antinuclear/analysis , Autoimmune Diseases/immunology , Mice, Mutant Strains/immunology , Nucleosomes/immunology , Amino Acid Sequence , Animals , Antibodies, Monoclonal/chemistry , Antibody Specificity , Base Sequence , Binding Sites, Antibody , DNA-Binding Proteins/metabolism , Female , Hybridomas/metabolism , Immunoglobulin Heavy Chains/chemistry , Immunoglobulin Variable Region/chemistry , Mice , Molecular Sequence DataABSTRACT
The binding of antinuclear antibody-positive juvenile arthritis (JA) sera to bovine thymus histones H1, H2A, H2B, H3, and H4 was studied by an enzyme-linked immunosorbent assay. Seventy-five percent of the JA patients tested positive for at least 1 antibody specificity. Antihistone antibodies were predominantly IgM, while IgG antibodies were less common and were restricted to histones H1 or H3. In the group of patients with JA of pauciarticular onset, antihistone antibodies were significantly more elevated in patients with past or present uveitis than in patients without a history of uveitis. Anti-H1 antibodies in JA patients were found to react mostly with determinants located in the carboxyl-terminal domain of the H1 molecule. Sera were also reactive with human histone H1(0) or chicken histone H5, which are H1 variants found only in nondividing cells.
