RESUMEN
Transverse myelitis (TM) is an idiopathic inflammatory disorder of the spinal cord. The authors observed cases of recurrent TM in patients where anti-Ro (SSA) antibodies were present and therefore performed a case-control study to examine the frequency of anti-Ro autoantibodies in patients with recurrent TM and control subjects. Antibodies to 52-kd Ro were demonstrated in 77% of cases (10/13) compared with only 33% of control subjects (4/12).
Asunto(s)
Autoanticuerpos/sangre , Autoantígenos , Mielitis Transversa/inmunología , ARN Citoplasmático Pequeño , Ribonucleoproteínas/inmunología , Adolescente , Adulto , Edad de Inicio , Anciano , Anticuerpos Antinucleares/sangre , Estudios de Casos y Controles , Femenino , Estudios de Seguimiento , Humanos , Masculino , Persona de Mediana Edad , Mielitis Transversa/diagnóstico , Recurrencia , Estudios RetrospectivosRESUMEN
Carboxypeptidases are proteases that cleave single amino acids from the carboxy termini of proteins or peptides. In addition to degradative functions in the gut, carboxypeptidases activate or inactivate bioactive peptides such as angiotensin, bradykinin, and endothelin I. Using differential display PCR, we cloned a novel carboxypeptidase expressed in human macrophages but not in other leukocytes. The 476-amino-acid gene product has a putative signal sequence but no transmembrane domain and has striking sequence similarity to serine carboxypeptidases, a large family of enzymes in eukaryotes. Only one serine carboxypeptidase, lysosomal protective protein, has previously been reported in mammals. Among known proteins, this gene is most similar (43% amino acid identity) to vitellogenic carboxypeptidase, a serine carboxypeptidase expressed in mosquito ovaries. Therefore, we have named this new gene carboxypeptidase, vitellogenic-like (CPVL). In addition to monocyte/macrophage-rich sources such as spleen, leukocytes, and placenta, CPVL mRNA is abundantly expressed in heart and kidney, suggesting a separate role for CPVL outside the immune system. The CPVL gene contains at least 13 exons spread over more than 150 kb on human chromosome 7p14-p15. An affinity-purified polyclonal antiserum recognized a protein of approximately 57 kDa in macrophage lysates, but not in lysates from lymphocytes, neutrophils, or monocytes. CPVL protein expression was induced during maturation of monocytes into macrophages. Possible functions for CPVL in macrophages include digestion of phagocytosed particles in the lysosome, participation in an inflammatory protease cascade, and trimming of peptides for antigen presentation.
Asunto(s)
Carboxipeptidasas/genética , Macrófagos/enzimología , Secuencia de Aminoácidos , Secuencia de Bases , Northern Blotting , Línea Celular , Células Cultivadas , Clonación Molecular , ADN Complementario/química , ADN Complementario/genética , Femenino , Expresión Génica , Células HeLa , Humanos , Células Jurkat , Datos de Secuencia Molecular , ARN Mensajero/genética , ARN Mensajero/metabolismo , Alineación de Secuencia , Análisis de Secuencia de ADN , Homología de Secuencia de Aminoácido , Distribución Tisular , Células Tumorales Cultivadas , Células U937RESUMEN
A soluble form of the mannose receptor (sMR) has been found in conditioned medium of primary macrophages in vitro and in mouse serum. sMR was released as a single species, had a smaller size than the cell-associated form, and accumulated in macrophage-conditioned medium, in a cytokine-regulated manner, to levels comparable with those found for cell-associated mannose receptor. Pulse-chase experiments showed that sMR production in culture occurred by constitutive cleavage of pre-existing full-length protein. A binding assay was developed to determine the sugar specificity of sMR and its ability to interact with pathogens and particulate antigens (i.e. Candida albicans and zymosan). Protease inhibitor studies suggested that sMR was produced by cleavage of an intact mannose receptor by a matrix metalloprotease or ADAM metalloprotease. A role for sMR in the immune response is proposed based on its binding properties, regulation by cytokines, and the previous discovery of putative ligands for the cysteine-rich domain of the mannose receptor in lymph nodes and spleen.
Asunto(s)
Lectinas Tipo C , Macrófagos Peritoneales/metabolismo , Lectinas de Unión a Manosa , Receptores de Superficie Celular/metabolismo , Secuencia de Aminoácidos , Animales , Células Cultivadas , Medios de Cultivo Condicionados/química , Fucosa/metabolismo , Galactosa/metabolismo , Ligandos , Macrófagos Peritoneales/citología , Manosa/metabolismo , Receptor de Manosa , Metaloendopeptidasas/antagonistas & inhibidores , Metaloendopeptidasas/metabolismo , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C57BL , Datos de Secuencia Molecular , SolubilidadRESUMEN
Gangliosides, added exogenously at concentrations of 10-100 microM, inhibit intrinsic protein kinase activities in purified rat brain myelin. Multivalent neoganglioproteins--gangliosides covalently attached, via their lipid moieties, to bovine serum albumin--were much more potent, inhibiting myelin protein phosphorylation half-maximally at a concentration of 100 nM. Different ganglioside conjugates varied 10-fold in inhibitory potency; GT1b-conjugates being the most potent and GM3-conjugates being the least. Conjugates of ganglioside oligosaccharides, lacking the lipid moiety, did not inhibit myelin protein phosphorylation, whereas conjugates of sphingosine inhibited nearly as potently as GT1b conjugates. Conjugate-mediated inhibition of myelin protein phosphorylation was due to inhibition of a protein serine kinase activity rather than activation of a phosphatase activity. We conclude that (i) clustered gangliosides or sphingosine are potent myelin protein kinase inhibitors, and (ii) sphingolipid metabolism is not required for myelin protein kinase inhibition. In contrast to their effects on myelin protein phosphorylation, ganglioside conjugates stimulated phosphorylation of a presumptive axon membrane protein. The data support the conclusion that gangliosides and other sphingolipids, when appropriately clustered, are potent modulators of central nervous system protein phosphorylation.
Asunto(s)
Proteínas Quinasas Dependientes de Calcio-Calmodulina/antagonistas & inhibidores , Gangliósidos/farmacología , Albúmina Sérica Bovina/farmacología , Esfingolípidos/farmacología , Animales , Encéfalo/enzimología , Membrana Celular/enzimología , Activación Enzimática , Gangliósidos/síntesis química , Glucógeno Sintasa Quinasa 3 , Masculino , Proteínas del Tejido Nervioso/metabolismo , Fosforilación/efectos de los fármacos , Ratas , Ratas Sprague-Dawley , Albúmina Sérica Bovina/síntesis química , Esfingolípidos/síntesis químicaRESUMEN
BACKGROUND: Protein-carbohydrate interactions are believed to be important in many biological processes that involve cell-cell communication. Apart from the selectins, the only well-characterized vertebrate sialic acid-dependent adhesion molecules are CD22 and sialoadhesin; CD22 is a member of the immunoglobulin superfamily that is expressed by B lymphocytes and sialoadhesin is a macrophage receptor. The recent cloning of the gene encoding sialoadhesin has shown that it is also immunoglobulin-like. Both proteins share sequence similarity with the myelin-associated glycoprotein, an adhesion molecule of oligodendrocytes and Schwann cells that has been implicated in the process of myelination, raising the important question of whether myelin-associated glycoprotein is also a sialic acid-binding protein. RESULTS: We have investigated the binding properties of these three receptors when expressed either in monkey COS cells or as chimaeric proteins containing the Fc portion of human immunoglobulin G. We demonstrate that, like sialoadhesin and CD22, myelin-associated glycoprotein mediates cell adhesion by binding to cell-surface glycans that contain sialic acid. We have dissected the specificities of these three adhesins further: whereas sialoadhesin binds equally to the sugar moieties NeuAc alpha 2-->3Gal beta 1-->3(4)GlcNAc or NeuAc alpha 2-->3Gal beta 1-->3GalNAc, myelin-associated glycoprotein recognizes only NeuAc alpha 2-->3Gal beta 1-->3GalNAc and CD22 binds specifically to NeuAc alpha 2-->6Gal beta 1-->4GlcNAc. Furthermore, we show that the recognition of sialylated glycans on the surfaces of particular cell types leads to the selective binding of sialoadhesin to neutrophils, myelin-associated glycoprotein to neurons and CD22 to lymphocytes. CONCLUSIONS: Our findings demonstrate that a subgroup of the immunoglobulin superfamily can mediate diverse biological processes through recognition of specific sialylated glycans on cell surfaces. We propose that this subgroup of proteins be called the sialoadhesin family.
Asunto(s)
Antígenos CD/metabolismo , Antígenos de Diferenciación de Linfocitos B/metabolismo , Moléculas de Adhesión Celular/metabolismo , Lectinas , Glicoproteínas de Membrana/metabolismo , Proteínas de la Mielina/metabolismo , Receptores Inmunológicos/metabolismo , Animales , Antígenos CD/química , Antígenos CD/genética , Antígenos de Diferenciación de Linfocitos B/química , Antígenos de Diferenciación de Linfocitos B/genética , Secuencia de Bases , Sitios de Unión , Metabolismo de los Hidratos de Carbono , Secuencia de Carbohidratos , Carbohidratos/química , Línea Celular , Membrana Celular/metabolismo , Cartilla de ADN/genética , Eritrocitos/metabolismo , Humanos , Glicoproteínas de Membrana/química , Glicoproteínas de Membrana/genética , Datos de Secuencia Molecular , Estructura Molecular , Proteínas de la Mielina/química , Proteínas de la Mielina/genética , Glicoproteína Asociada a Mielina , Neuronas/metabolismo , Receptores de Superficie Celular/metabolismo , Receptores Inmunológicos/química , Receptores Inmunológicos/genética , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/metabolismo , Lectina 1 Similar a Ig de Unión al Ácido Siálico , Lectina 2 Similar a Ig de Unión al Ácido Siálico , Ácidos Siálicos/química , Ácidos Siálicos/metabolismoRESUMEN
We have previously shown that the expression of the gene encoding murine beta 1,4-galactosyltransferase (beta 1,4-GT, UDP-galactose:N-acetyl-D-glucosaminyl-glycopeptide 4-beta-D galactosyltransferase, EC 2.4.1.38) is fundamentally different between somatic and male germ cells (Shaper et al., 1990b). In somatic cells, two transcripts of 3.9 kb and 4.1 kb are produced. In contrast, in spermatogonia only the 4.1 kb transcript is expressed. Maturation of spermatogonia to pachytene spermatocytes is accompanied by reduced expression of the 4.1 kb transcript to barely detectable levels. Continued differentiation to haploid round spermatids is coincident with renewed expression in which the 4.1 kb transcript is replaced by two truncated transcripts of 2.9 and 3.1 kb. In this study, we report the characterization of a full-length beta 1,4-GT cDNA clone from a murine round spermatid library that corresponds to the 2.9 kb transcript. This transcript encodes the same open reading frame as the 4.1 kb transcript, but utilizes alternative poly(A) signals embedded within the long 3'-untranslated region of the somatic transcript. Based on sequence analysis, together with primer extension and S1 nuclease protection experiments, both the 2.9 and the 3.1 kb round spermatid beta 1,4-GT transcripts are distinguished by the presence of an additional 5'-untranslated sequence of approximately 560 bp that is absent in premeiotic germ cells and somatic cells.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Espermátides/enzimología , beta-N-Acetilglucosaminilglicopéptido beta-1,4-Galactosiltransferasa/genética , Animales , Secuencia de Bases , ADN/química , ADN/genética , ADN/aislamiento & purificación , Masculino , Ratones , Datos de Secuencia Molecular , Conformación de Ácido Nucleico , Biosíntesis de Proteínas , ARN/química , Mapeo Restrictivo , Endonucleasas Específicas del ADN y ARN con un Solo Filamento , Transcripción GenéticaRESUMEN
A contrast agent that is selectively accumulated in the liver should greatly improve the diagnostic value of contrast enhanced CT scanning. The advantages and disadvantages of different classes of hepatographic agents are briefly reviewed. Experimental results obtained with the particulate contrast agents, iothalamate ethyl ester and iodipamide ethyl ester, are presented in more detail. Following intravenous infusion of iodipamide ethyl ester, approximately 60% of the injected dose is accumulated in the rat liver. CT scanning experiments involving iothalamate ethyl ester infusions in New Zealand White rabbits demonstrate significantly higher liver contrast enhancement at 10-30 minutes postinfusion than is observed with diatrizoate at a sixfold greater iodine dose. The selective accumulation of a particulate contrast agent in hepatic reticuloendothelial cells compared to virtually no accumulation in implanted VX2 carcinoma demonstrates the important potential value of these agents in improving detection of liver metastases.
Asunto(s)
Medios de Contraste , Hígado/diagnóstico por imagen , Tomografía Computarizada por Rayos X , Animales , Medios de Contraste/metabolismo , Diatrizoato/metabolismo , Esterasas/metabolismo , Yodipamida/metabolismo , Ácido Yotalámico/metabolismo , Hígado/metabolismo , Tamaño de la Partícula , Conejos , Ratas , Solubilidad , Distribución TisularRESUMEN
Particulate contrast agents, when compared to water-soluble media, offer the advantage of allowing the administration of high doses without creating hypertonicity gradients and ionic imbalances. Since these radiopaque particles are accumulated in the reticuloendothelial system, they could be ideal hepatic CT contrast agents. We have developed a method for making particles of 2 +/- 1 microns by precipitating from an organic solvent. Preincubation of these particles in human serum albumin overcomes the very serious problem of in vivo particle aggregation and embolization. The ethyl esters of iothalamic and iodipamic acid have been injected intravenously into mice, rats, and rabbits. Radiopacification of the liver is maximal within 2-3 hours postinfusion, with radiopaque material subsequently clearing through the biliary system. Elimination from the organism seems to be complete within a few days postinfusion. Efforts to decrease the subacute toxicity of these agents are underway.
Asunto(s)
Medios de Contraste/metabolismo , Tamaño de la Partícula , Tomografía Computarizada por Rayos X , Animales , Medios de Contraste/síntesis química , Medios de Contraste/toxicidad , Perros , Humanos , Yodipamida/análogos & derivados , Ácido Yotalámico/análogos & derivados , Hígado/diagnóstico por imagen , Sistema Mononuclear Fagocítico/metabolismo , Unión Proteica , Conejos , Ratas , Albúmina Sérica , Relación Estructura-ActividadRESUMEN
Contrast enhancement of the liver of anesthetized, paralyzed, and artificially ventilated rabbits was measured during suspended respiration prior to, during, and after the intravenous infusion of meglumine diatrizoate at doses of 208, 416, and 624 mg I/kg. Infusion time was 30 seconds, and, at the highest dose, infusion times of 1, 2, and 4 minutes were also used. Highest contrast enhancement values were obtained at the conclusion of each infusion, with contrast enhancement increasing proportionately with increase in dose. Highest enhancement was obtained at all times studied from the most rapid infusion. Unlike cranial CT, optimum hepatic contrast enhancement in body CT requires rapid contrast medium injection with immediate CT scanning with a very fast scanner.