RESUMEN
Two novel members of the interleukin-1 receptor (IL-1R) family, identified by homology searches of human genomic sequence data bases, are described. The genes have been named according to their structural features: TIGIRR-1 (three immunoglobulin domain-containing IL-1 receptor-related) and TIGIRR-2. TIGIRR-2 has recently been identified as causing mental retardation when mutated (Carrie, A., Jun, L., Bienvenu, T., Vinet, M. C., McDonell, N., Couvert, P., Zemni, R., Cardona, A., Van Buggenhout, G., Frints, S., Hamel, B., Moraine, C., Ropers, H. H., Strom, T., Howell, G. R., Whittaker, A., Ross, M. T., Kahn, A., Fryns, J. P., Beldjord, C., Marynen, P., and Chelly, J. (1999) Nat. Genet. 23, 25-31) and called IL1RAPL, a name we will also use henceforth. Neither receptor alone was able to mediate transcriptional activation of NF-kappaB in response to IL-1alpha, IL-1beta, or IL-18. In order to begin to elucidate the function of these and other orphan IL-1R family members, we have developed a functional assay utilizing a panel of chimeric receptors containing the extracellular and transmembrane domains of either type I IL-1R or IL-1R accessory protein (AcP) coupled to the cytoplasmic domains of all family members. Coexpression of each IL-1R chimera with each AcP chimera and an NF-kappaB-responsive reporter demonstrated that the cytoplasmic domains could be classified as IL-1R-like, AcP-like, or neither. Any IL-1R-like cytoplasmic domain could cooperate with any AcP-like cytoplasmic domain. The TIGIRR-1 and IL1RAPL cytoplasmic domains, however, were unable to signal as either IL-1R-like or AcP-like components, suggesting that they function as a new class of receptors within this family.
Asunto(s)
Familia de Multigenes , Receptores de Interleucina-1/metabolismo , Secuencia de Aminoácidos , Biblioteca Genómica , Humanos , Interleucina-1/metabolismo , Proteína Accesoria del Receptor de Interleucina-1 , Interleucina-18/metabolismo , Datos de Secuencia Molecular , FN-kappa B/metabolismo , Proteínas/genética , Proteínas/metabolismo , Receptores de Interleucina-1/clasificación , Receptores de Interleucina-1/genética , Proteínas Recombinantes de Fusión/metabolismo , Homología de Secuencia de Aminoácido , Transducción de SeñalRESUMEN
We report here the cloning and characterization of four new members of the interleukin-1 (IL-1) family (FIL1delta, FIL1epsilon, FIL1zeta, and FIL1eta, with FIL1 standing for "Family of IL-1"). The novel genes demonstrate significant sequence similarity to IL-1alpha, IL-1beta, IL-1ra, and IL-18, and in addition maintain a conserved exon-intron arrangement that is shared with the previously known members of the family. Protein structure modeling also suggests that the FIL1 genes are related to IL-1beta and IL-1ra. The novel genes form a cluster with the IL-1s on the long arm of human chromosome 2.
Asunto(s)
Cromosomas Humanos Par 2 , Interleucina-1/genética , Familia de Multigenes , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Línea Celular , Mapeo Cromosómico , Clonación Molecular , Secuencia Conservada , Exones , Femenino , Biblioteca Genómica , Humanos , Interleucina-1/química , Interleucina-1/metabolismo , Intrones , Masculino , Ratones , Modelos Moleculares , Datos de Secuencia Molecular , Sistemas de Lectura Abierta , Conformación Proteica , Isoformas de Proteínas/química , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Estructura Secundaria de Proteína , Receptores de Interleucina-1/metabolismo , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Alineación de Secuencia , Homología de Secuencia de Aminoácido , Células Tumorales CultivadasRESUMEN
A novel member of the interleukin 1 receptor (IL-1R) superfamily, SIGIRR (single Ig IL-1R-related molecule) was identified in mouse and human. Although it shows the typical conserved motifs that characterize the IL-1R and Toll superfamily, it is structurally and functionally distinct from both. SIGIRR has only one Ig domain in its extracellular portion whereas the IL-1R family contains three Ig folds. An unusually long cytoplasmic domain is reminiscent of the structure of drosophila Toll, yet the SIGIRR peptide sequence is more closely related to IL-1RI. The human SIGIRR gene maps to 11p15. 5 and thus is not located in the same cluster on chromosome 2 that is known to contain four members of the IL-1R family. It failed to bind to the known IL-1-family members and, when co-expressed with the IL-1RI, had no effect on the binding of IL-1 and on subsequent nuclear factor kappaB (NFkappaB) activation. A chimera, in which the SIGIRR intracellular domain was fused to the IL-1R extracellular domain, did not activate NFkappaB unlike similar fusion proteins of other IL-1R related molecules. We conclude that the SIGIRR protein represents a novel subtype of the IL-1R superfamily.
Asunto(s)
Inmunoglobulinas/genética , Familia de Multigenes , Receptores de Interleucina-1/genética , Secuencia de Aminoácidos , Animales , Reacciones Antígeno-Anticuerpo , Western Blotting , Línea Celular , Mapeo Cromosómico , Clonación Molecular , Humanos , Ratones , Datos de Secuencia Molecular , ARN Mensajero/biosíntesis , Homología de Secuencia de Aminoácido , Transducción de Señal/fisiologíaRESUMEN
Interleukin-18 (IL-18) is an inflammatory cytokine that has been shown to enhance a variety of Th1 type T cell responses. Because IL-18 is homologous to IL-1, we tested binding of IL-18 to the known IL-1R family members. We could show binding of IL-18 to the orphan receptor IL-1Rrp1 but not to other IL-1R homologous proteins. IL-1Rrp1 and IL-1RI share highly conserved domains within their cytoplasmic regions. Comparison of the IL-1 and IL-18 signaling mechanisms showed that they activate identical cytoplasmic messengers. IL-18, like IL-1, induced association of its receptor with IRAK and subsequent recruitment of TRAF6. IL-18 activated p38 MAP kinase, jun kinase, and beta casein kinase (TIP kinase), an apparently novel kinase previously thought to be specifically activated by IL-1 and tumor necrosis factor (TNF). IL-18 activated NF-kappaB in EL4/6.1 thymoma cells but not in COS-7 cells, even though the latter presumably contain all components required for the IL-1 signaling pathway. From our binding and signaling studies, we conclude that the IL-18 receptor complex consists of IL-18, the IL-1Rrp1, and another thus far unidentified receptor molecule.
Asunto(s)
Caseína Quinasas , Interleucina-18/metabolismo , Interleucina-1/metabolismo , Receptores de Interleucina-1/metabolismo , Transducción de Señal/fisiología , Animales , Células COS , Proteínas Quinasas Dependientes de Calcio-Calmodulina/metabolismo , Línea Celular , Activación Enzimática , Humanos , Ratones , FN-kappa B/metabolismo , Pruebas de Precipitina , Proteínas Quinasas/metabolismoRESUMEN
T1/ST2 is a receptor-like molecule homologous to the type I interleukin-1 receptor. Despite this sequence similarity, we have been unable to demonstrate binding of T1/ST2 to any of the three interleukin-1 species. In searching for a ligand for T1/ST2, we have cloned a cell surface protein to which it binds. This protein is unable to initiate signal transduction by the T1/ST2 receptor in several in vitro assays.
Asunto(s)
Proteínas de la Membrana , Proteínas/metabolismo , Receptores de Interleucina-1/metabolismo , Células 3T3 , Secuencia de Aminoácidos , Animales , Línea Celular , Clonación Molecular , ADN/metabolismo , Femenino , Humanos , Proteína 1 Similar al Receptor de Interleucina-1 , Interleucina-8/genética , Cinética , Ratones , Datos de Secuencia Molecular , FN-kappa B/metabolismo , Especificidad de Órganos , Regiones Promotoras Genéticas , Biosíntesis de Proteínas , Ratas , Receptores de Superficie Celular , Receptores de Interleucina , Receptores de Interleucina-1/biosíntesis , Receptores de Interleucina-1/química , Proteínas Recombinantes/biosíntesis , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Homología de Secuencia de Aminoácido , Especificidad por Sustrato , Células Tumorales CultivadasRESUMEN
The low-affinity receptor for leukemia inhibitory factor (LIFR) interacts with gp130 to induce an intracellular signal cascade. The LIFR-gp130 heterodimer is implicated in the function of diverse systems. Normal placentation is disrupted in LIFR mutant animals, which leads to poor intrauterine nutrition but allows fetuses to continue to term. Fetal bone volume is reduced greater than three-fold and the number of osteoclasts is increased six-fold, resulting in severe osteopenia of perinatal bone. Astrocyte numbers are reduced in the spinal cord and brain stem. Late gestation fetal livers contain relatively high stores of glycogen, indicating a metabolic disorder. Hematologic and primordial germ cell compartments appear normal. Pleiotropic defects in the mutant animals preclude survival beyond the day of birth.
Asunto(s)
Desarrollo Embrionario y Fetal , Inhibidores de Crecimiento , Interleucina-6 , Linfocinas/genética , Receptores de Citocinas/genética , Animales , Astrocitos/citología , Secuencia de Bases , Southern Blotting , Desarrollo Óseo , Recuento de Células , Cartilla de ADN/genética , Muerte Fetal/genética , Eliminación de Gen , Glucógeno/metabolismo , Hematopoyesis/fisiología , Factor Inhibidor de Leucemia , Subunidad alfa del Receptor del Factor Inhibidor de Leucemia , Hígado/embriología , Hígado/metabolismo , Ratones , Ratones Transgénicos , Datos de Secuencia Molecular , Mutagénesis Insercional , Sistema Nervioso/embriología , Osteoclastos/citología , Placenta/fisiología , Reacción en Cadena de la Polimerasa , Receptores OSM-LIF , Células Madre/fisiologíaRESUMEN
Individuals with X-linked hyper-IgM syndrome fail to express functional CD40 ligand (CD40L) and, as a consequence, are incapable of mounting protective antibody responses to opportunistic bacterial infections. To address the role of CD40L in humoral immunity, we created, through homologous recombination, mice deficient in CD40L expression. These mice exhibited no gross developmental deficiencies or health abnormalities and contained normal percentages of B and T cell subpopulations. CD40L-deficient mice did display selective deficiencies in humoral immunity; basal serum isotype levels were significantly lower than observed in normal mice, and IgE was undetectable. Furthermore, the CD40L-deficient mice failed to mount secondary antigen-specific responses to immunization with a thymus-dependent antigen, trinitrophenol-conjugated keyhole limpet hemocyanin (TNP-KLH). By contrast, the CD40L-deficient mice produced antigen-specific antibody of all isotypes except IgE in response to the thymus-independent antigen, DNP-Ficoll. These results underscore the requirement of CD40L for T cell-dependent antibody responses. Moreover, Ig class switching to isotypes other than IgE can occur in vivo in the absence of CD40L, supporting the notion that alternative B cell signaling pathways regulate responses to thymus-independent antigens.