RESUMEN
SUMOylation is a post-translational modification (PTM) that exerts a regulatory role in different cellular processes, including protein localization, aggregation, and biological activities. It consists of the dynamic formation of covalent isopeptide bonds between a family member of the Small Ubiquitin Like Modifiers (SUMOs) and the target proteins. Interestingly, it is a cellular mechanism implicated in several neurodegenerative pathologies and potentially it could become a new therapeutic target; however, there are very few pharmacological tools to modulate the SUMOylation process. In this study, we have designed and tested the activity of a novel small cell-permeable peptide, COV-1, in a neuroblastoma cell line that specifically prevents protein SUMOylation. COV-1 inhibits UBC9-protein target interaction and efficiently decreases global SUMO-1ylation. Moreover, it can perturb RanGAP-1 perinuclear localization by inducing the downregulation of UBC9. In parallel, we found that COV-1 causes an increase in the ubiquitin degradation system up to its engulfment while enhancing the autophagic flux. Surprisingly, COV-1 modifies protein aggregation, and specifically it mislocalizes TDP-43 within cells, inducing its aggregation and co-localization with SUMO-1. These data suggest that COV-1 could be taken into future consideration as an interesting pharmacological tool to study the cellular cascade effects of SUMOylation prevention.
Asunto(s)
Proteínas de Unión al ADN , Sumoilación , Proteínas de Unión al ADN/metabolismo , Línea Celular , Ubiquitina/metabolismo , Péptidos/metabolismoRESUMEN
INTRODUCTION: Immunosuppressive state due to haematological malignancies and chemotherapy may cause disruption to wound healing despite optimum conventional treatment and standard wound dressing. Non-healing wounds are predisposed to infection whereas chemotherapy dose reductions or interruptions are associated with poor survival. BACKGROUND: Mononuclear cells contain progenitor cells including haematopoietic and mesenchymal stem cells, endothelial progenitor cells and fibroblasts which facilitate wound healing through cytokines, growth factor secretions, cell-cell interactions and provision of extracellular matrix scaffolding. Clinical applications of autologous mononuclear cells therapy in wound healing in non-malignant patients with critical limb ischaemia have been reported with remarkable outcome. METHODS: We report three patients with haematological malignancies undergoing chemotherapy, who received autologous mononuclear cells implantation to treat non-healing wound after optimum conventional wound care. The sources of mononuclear cells (MNC) were from bone marrow (BM), peripheral blood (PB) and mobilised PB cells (mPB-MNC) using granulocyte colony stimulating factor (G-CSF). The cells were directly implanted into wound and below epidermis. Wound sizes and adverse effects from implantation were assessed at regular intervals. RESULTS: All patients achieved wound healing within three months following autologous mononuclear cells implantation. No implantation adverse effects were observed. CONCLUSIONS: Autologous mononuclear cells therapy is a feasible alternative to conventional wound care to promote complete healing in non-healing wounds compounded by morbid factors such as haematological malignancies, chemotherapy, diabetes mellitus (DM), infections and prolonged immobility.
Asunto(s)
Neoplasias Hematológicas/complicaciones , Leucocitos Mononucleares/trasplante , Cicatrización de Heridas , Adolescente , Anciano , Femenino , Humanos , Masculino , Trasplante Autólogo/métodosRESUMEN
A rapid and simple chemical synthesis of poly(2-aminothiophenol)silver (P2ATP-Ag) nanocomposite using conductive and electroactive silver nanoparticles (AgNPs) is reported. The AgNPs was synthesized by chemical reduction method using trisodium citrate as reducing agent and poly(N-vinyl-2-pyrrolidone) (PVP) as stabilizing agent. P2ATP-Ag nanocomposite was synthesized by using potassium peroxodisulphate as oxidant and the samples were characterized. The presence of AgNPs in the composite was confirmed from UV-Vis, FTIR and X-ray diffraction studies. Morphology of the P2ATP and its composite were investigated by SEM. HR-TEM images show spherical, trigonal and rod like morphologies with sizes of Ag nanoparticles and its composite. Thermal analysis revealed that the thermal stability of the P2ATP-Ag nanocomposite is improved when compared with pure P2ATP. The synthesized AgNPs, pure P2ATP and P2ATP-Ag nanocomposite were screened for antibacterial activity test against human pathogen such as Gram positive (Bacillus subtilis, ATCC-6051) and Gram negative (Vibrio cholerae, ATCC-14035), carried out by agar-well diffusion method at micro molar concentration. The result shows that P2ATP-Ag nanocomposite has excellent antibacterial activity due to the presence of Ag nanoparticles. The electrical conductivity of the P2ATP-Ag nanocomposite is better than that of pure P2ATP. The reported nanocomposite will be a potential material for electrocatalysis, sensors and biomedical applications.
Asunto(s)
Antibacterianos/química , Nanopartículas del Metal/química , Polímeros/química , Plata/química , Antibacterianos/síntesis química , Antibacterianos/farmacología , Bacillus subtilis/efectos de los fármacos , Conductividad Eléctrica , Humanos , Nanopartículas del Metal/toxicidad , Pruebas de Sensibilidad Microbiana , Microscopía Electrónica de Rastreo , Espectrofotometría Ultravioleta , Espectroscopía Infrarroja por Transformada de Fourier , Difracción de Rayos XRESUMEN
Immune Thrombocytopenia Purpura (ITP) secondary to vaccinations is rare, especially after autologous hematopoietic stem cell transplantation (HSCT). A 31-yearold female received autologous HSCT for relapsed Hodgkin Disease, with platelet engraftment at Day+14. One week after receiving second scheduled vaccinations, she developed severe thrombocytopenia (3x109/L) associated with pharyngeal hematoma. Bone marrow (BM) examinations were consistent with ITP, possibly secondary to Influenza vaccine. Platelet increment was poor despite high dose corticosteroids, intravenous immunoglobulin (IVIG), Danazol and Eltrombopag. A repeated BM biopsy was in agreement with ITP. Re-treatment with tapering doses of prednisolone resulted in stable platelet counts at 120x109/L a year later.
Asunto(s)
Trasplante de Células Madre Hematopoyéticas/efectos adversos , Púrpura Trombocitopénica Idiopática/etiología , Vacunas/efectos adversos , Adulto , Vacuna contra Difteria, Tétanos y Tos Ferina/efectos adversos , Femenino , Vacunas contra Haemophilus/efectos adversos , Vacunas contra Hepatitis B/efectos adversos , Enfermedad de Hodgkin/cirugía , Humanos , Vacunas contra la Influenza/efectos adversos , Vacunas Neumococicas/efectos adversos , Trasplante Autólogo/efectos adversosRESUMEN
Apolipoprotein E (apoE) plays a critical role in cholesterol transport in both peripheral circulation and brain. Human apoE is a polymorphic 299-residue protein in which the less common E4 isoform differs from the major E3 isoform only by a C112R substitution. ApoE4 interacts with lipoprotein particles and with the amyloid-ß peptide, and it is associated with increased incidence of cardiovascular and Alzheimer's disease. To understand the structural basis for the differences between apoE3 and E4 functionality, we used hydrogen-deuterium exchange coupled with a fragment separation method and mass spectrometric analysis to compare their secondary structures at near amino acid resolution. We determined the positions, dynamics, and stabilities of the helical segments in these two proteins, in their normal tetrameric state and in mutation-induced monomeric mutants. Consistent with prior X-ray crystallography and NMR results, the N-terminal domain contains four α-helices, 20 to 30 amino acids long. The C-terminal domain is relatively unstructured in the monomeric state but forms an α-helix â¼70 residues long in the self-associated tetrameric state. Helix stabilities are relatively low, 4 kcal/mol to 5 kcal/mol, consistent with flexibility and facile reversible unfolding. Secondary structure in the tetrameric apoE3 and E4 isoforms is similar except that some helical segments in apoE4 spanning residues 12 to 20 and 204 to 210 are unfolded. These conformational differences result from the C112R substitution in the N-terminal helix bundle and likely relate to a reduced ability of apoE4 to form tetramers, thereby increasing the concentration of functional apoE4 monomers, which gives rise to its higher lipid binding compared with apoE3.
Asunto(s)
Apolipoproteína E3/química , Apolipoproteína E4/química , Espectrometría de Masas/métodos , Sustitución de Aminoácidos , Apolipoproteína E4/genética , Dicroismo Circular , Predisposición Genética a la Enfermedad , Hidrógeno/metabolismo , Interacciones Hidrofóbicas e Hidrofílicas , Lipoproteínas/metabolismo , Mutación Missense , Mutación Puntual , Unión Proteica , Dominios Proteicos , Pliegue de Proteína , Isoformas de Proteínas/química , Isoformas de Proteínas/genética , Multimerización de Proteína , Estructura Secundaria de Proteína , Proteínas Recombinantes de Fusión/químicaRESUMEN
Infection or inflammation may precede and trigger formation of microvascular thrombosis in patients with acquired thrombotic thrombocytopenic purpura (TTP). However, the mechanism underlying this clinical observation is not fully understood. Here, we show that human neutrophil peptides (HNPs) released from activated and degranulated neutrophils inhibit proteolytic cleavage of von Willebrand factor (VWF) by ADAMTS13 in a concentration-dependent manner. Half-maximal inhibitory concentrations of native HNPs toward ADAMTS13-mediated proteolysis of peptidyl VWF73 and multimeric VWF are 3.5 µM and 45 µM, respectively. Inhibitory activity of HNPs depends on the RRY motif that is shared by the spacer domain of ADAMTS13. Native HNPs bind to VWF73 (KD = 0.72 µM), soluble VWF (KD = 0.58 µM), and ultra-large VWF on endothelial cells. Enzyme-linked immunosorbent assay (ELISA) demonstrates markedly increased plasma HNPs1-3 in most patients with acquired autoimmune TTP at presentation (median, â¼170 ng/mL; range, 58-3570; n = 19) compared with healthy controls (median, â¼23 ng/mL; range, 6-44; n = 18) (P < .0001). Liquid chromatography plus tandem mass spectrometry (LC-MS/MS) reveals statistically significant increases of HNP1, HNP2, and HNP3 in patient samples (all P values <.001). There is a good correlation between measurement of HNPs1-3 by ELISA and by LC-MS/MS (Spearman ρ = 0.7932, P < .0001). Together, these results demonstrate that HNPs1-3 may be potent inhibitors of ADAMTS13 activity, likely by binding to the central A2 domain of VWF and physically blocking ADAMTS13 binding. Our findings may provide a novel link between inflammation/infection and the onset of microvascular thrombosis in acquired TTP and potentially other immune thrombotic disorders.
Asunto(s)
Proteína ADAMTS13/metabolismo , Defensinas/metabolismo , Neutrófilos/metabolismo , Proteolisis , Púrpura Trombocitopénica Trombótica/metabolismo , Factor de von Willebrand/metabolismo , Secuencias de Aminoácidos , Femenino , Humanos , Inflamación/metabolismo , Inflamación/patología , Masculino , Neutrófilos/patología , Púrpura Trombocitopénica Trombótica/patologíaRESUMEN
Tuberculosis, an ancient disease continues to be a health care burden in Malaysia in the 21st century. Extrapulmonary tuberculosis is a less common presentation of tuberculosis and in particular peripancreatic tuberculous lymphadenitis is rarely seen. We report a case of a young immunocompetent boy presenting with a two month history of non productive chronic cough associated with loss of appetite and loss of weight. Investigations including CT Scan and Endoscopic ultrasound revealed multiple mediastinal lymphadenopathy and peripancreatic lymphadenopathy with central caseation necrosis. Histology of cervical lymph node was suggestive of tuberculosis and mycobacterium PCR was positive. The patient was subsequently treated with antituberculous therapy and had marked clinical improvement of his symptoms. This case outlines a rare presentation of a common disease and the application of newer investigative tools in making the diagnosis.
RESUMEN
UNLABELLED: High resolution esophageal manometry (HREM) has been interpreted all along by visual interpretation of color plots until the recent introduction of Chicago classification which categorises HREM using objective measurements. It compares HREM diagnosis of esophageal motor disorders by visual interpretation and Chicago classification. Using software Trace 1.2v, 77 consecutive tracings diagnosed by visual interpretation were re-analyzed by Chicago classification and findings compared for concordance between the two systems of interpretation. STATISTICAL ANALYSIS: Kappa agreement rate between the two observations was determined. There were 57 males (74 %) and cohort median age was 41 years (range: 14-83 years). Majority of the referrals were for gastroesophageal reflux disease, dysphagia and achalasia. By "intuitive" visual interpretation, the tracing were reported as normal in 45 (58.4 %), achalasia 14 (18.2 %), ineffective esophageal motility 3 (3.9 %), nutcracker esophagus 11 (14.3 %) and nonspecific motility changes 4 (5.2 %). By Chicago classification, there was 100 % agreement (Kappa 1) for achalasia (type 1: 9; type 2: 5) and ineffective esophageal motility ("failed peristalsis" on visual interpretation). Normal esophageal motility, nutcracker esophagus and nonspecific motility disorder on visual interpretation were reclassified as rapid contraction and esophagogastric junction (EGJ) outflow obstruction by Chicago classification. Chicago classification identified distinct clinical phenotypes including EGJ outflow obstruction not identified by visual interpretation. A significant number of unclassified HREM by visual interpretation were also classified by it.
Asunto(s)
Trastornos de la Motilidad Esofágica/clasificación , Trastornos de la Motilidad Esofágica/diagnóstico , Aumento de la Imagen/métodos , Interpretación de Imagen Asistida por Computador/métodos , Manometría/métodos , Adolescente , Adulto , Anciano , Femenino , Reflujo Gastroesofágico/diagnóstico , Humanos , Masculino , Persona de Mediana Edad , Programas Informáticos , Adulto JovenRESUMEN
Apolipoprotein A-I (apoA-I) Nichinan, a naturally occurring variant with DeltaE235 in the C terminus, is associated with low plasma HDL levels. Here, we investigated the tertiary structure, lipid-binding properties, and ability to induce cellular cholesterol efflux of apoA-I Nichinan and its C-terminal peptide. Thermal and chemical denaturation experiments demonstrated that the DeltaE235 mutation decreased the protein stability compared with wild type (WT). ApoA-I Nichinan exhibited capabilities to bind to or solubilize lipid vesicles that are intermediate to that of WT and a L230P/L233P/Y236P variant in which the C-terminal alpha-helix folding is completely disrupted and forms relatively larger and unstable discoidal complexes, indicating that perturbation of the C-terminal alpha-helical structure by the DeltaE235 mutation leads to reduced lipid binding. Supporting this, apoA-I 209-241/DeltaE235 peptide showed significantly decreased ability to form alpha-helix both in the lipid-free and lipid-bound states, and reduced efficiency to solubilize vesicles. In addition, both apoA-I Nichinan and its C-terminal peptide exhibited reduced activity in ABCA1-mediated cellular cholesterol efflux. Thus, the disruption of the ability of the C-terminal region to form alpha-helix caused by the E235 deletion appears to be the important determinant of impaired lipid binding and cholesterol efflux ability and, consequently, the low plasma HDL levels of apoA-I Nichinan probands.
Asunto(s)
Apolipoproteína A-I/genética , Apolipoproteína A-I/metabolismo , Colesterol/metabolismo , Transportador 1 de Casete de Unión a ATP , Transportadoras de Casetes de Unión a ATP/genética , Transportadoras de Casetes de Unión a ATP/metabolismo , Secuencia de Aminoácidos , Animales , Apolipoproteína A-I/química , Línea Celular , Dicroismo Circular , Cricetinae , Calor , Humanos , Interacciones Hidrofóbicas e Hidrofílicas , Ratones , Mutagénesis Sitio-Dirigida , Proteínas Mutantes/química , Proteínas Mutantes/metabolismo , Fragmentos de Péptidos/química , Fragmentos de Péptidos/metabolismo , Unión Proteica , Desnaturalización Proteica , Estabilidad Proteica , Estructura Secundaria de Proteína/genética , Estructura Terciaria de Proteína , Factores de Tiempo , Liposomas Unilamelares/químicaRESUMEN
Adipokinetic hormone (AKH) is the main hormone involved in the acute regulation of hemolymph lipid levels in several insects. In adult Manduca sexta AKH promotes a rapid phosphorylation of "Lipid storage protein-1", Lsd1, and a concomitant activation of the rate of hydrolysis of triglycerides by the main fat body lipase. In contrast, in the larval stage AKH modulates hemolymph trehalose levels. The present study describes the sequence of a full-length Lsd1 cDNA obtained from M. sexta fat body and investigates a possible link between Lsd1 expression and the distinct effects of AKH in larva and adult insects. The deduced protein sequence showed a high degree of conservation compared to other insect Lsd1s, particularly in the central region of the protein (amino acids 211-276) in which the predicted lipid binding helices are found. Lsd1 was absent in feeding larva and its abundance progressively increased as the insect develops from the non-feeding larva to adult. Contrasting with the levels of protein, Lsd1 transcripts were maximal during the feeding larval stages. The subcellular distribution of Lsd1 showed that the protein exclusively localizes in the lipid droplets. Lsd1 was found in the fat body but it was undetectable in lipid droplets isolated from oocytes or embryos. The present study suggests a link between AKH-stimulated lipolysis in the fat body and the expression of Lsd1.
Asunto(s)
Hormonas de Insectos/fisiología , Proteínas de Insectos/metabolismo , Metabolismo de los Lípidos , Manduca/metabolismo , Oligopéptidos/fisiología , Ácido Pirrolidona Carboxílico/análogos & derivados , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Clonación Molecular , Secuencia Conservada , ADN Complementario/química , Cuerpo Adiposo/metabolismo , Hormonas de Insectos/farmacología , Proteínas de Insectos/análisis , Proteínas de Insectos/genética , Manduca/efectos de los fármacos , Manduca/genética , Manduca/crecimiento & desarrollo , Datos de Secuencia Molecular , Oligopéptidos/farmacología , Ácido Pirrolidona Carboxílico/farmacología , Alineación de SecuenciaRESUMEN
BACKGROUND: Mycophenolate mofetil (MMF) is an immunomodulatory drug, and its use in inflammatory bowel disease has previously been reported. The aim of this study was to review the Leeds Colitis Clinic experience of the safety and efficacy of MMF in treating patients with refractory Crohn's disease (CD) and ulcerative colitis (UC). This is an extension of a previously published study from our center with a longer follow-up period and approximately twice the number of patients. METHODS: A retrospective analysis was performed of the records of all patients treated with MMF for inflammatory bowel disease over a 5-year period. RESULTS: Of 70 patients identified, 67 had previously been treated with azathioprine unsuccessfully. Seventeen of the 70 patients had been successfully maintained in remission with MMF for an average duration of 33 months. Treatment with MMF was discontinued for 53 patients, 17 because of side effects and 36 because they had not responded to the treatment. CONCLUSIONS: In our series, 17 patients (24.3%) had a sustained steroid-free remission with MMF therapy. Nineteen patients (27%) experienced side effects, of which 17 (24.3% of the total group) had to discontinue therapy. An additional 36 (51.4%) required an escalation in medical therapy or surgery because of failure of the MMF therapy. MMF may have a role in the treatment of refractory inflammatory bowel disease, especially in patients who have previously failed standard therapies such as azathioprine.
Asunto(s)
Colitis Ulcerosa/tratamiento farmacológico , Enfermedad de Crohn/tratamiento farmacológico , Inmunosupresores/efectos adversos , Inmunosupresores/uso terapéutico , Ácido Micofenólico/análogos & derivados , Adulto , Anciano , Anciano de 80 o más Años , Azatioprina/uso terapéutico , Femenino , Estudios de Seguimiento , Humanos , Masculino , Persona de Mediana Edad , Ácido Micofenólico/efectos adversos , Ácido Micofenólico/uso terapéutico , Estudios RetrospectivosAsunto(s)
Hepatitis A/complicaciones , Hepatitis Autoinmune/etiología , Enfermedad Aguda , Femenino , HumanosRESUMEN
The structure of Locusta migratoria apolipophorin-III consists of a five-helix bundle connected by four short loops. The role of the conformational flexibility of helices and loops on the lipid-binding activity of this apolipoprotein was investigated by disulfide mediated tethering experiments. One disulfide mutant tethering the second and fourth loops (L2-L4), and two disulfide mutants restricting the flexibility of the neighboring alpha-helices 3 and 4 (H3-H4) and 1 and 5 (H1-H5), were studied. The ability of the disulfide mutants to interact with phospholipid vesicles, mixed micelles of phosphatidylcholine and cholate, and in vivo with native spherical lipoprotein particles was studied. The L2-L4 mutant was active with native lipoproteins as well as being able to form discoidal lipoproteins upon incubation with either liposomes or discoidal micelles. The H3-H4 mutant was not able to interact with liposomes or native lipoproteins but interacted with discoidal micelles. The H1-H5 mutant was unable to interact with lipid in any of the three systems. Three conclusions were reached: (1) opening of the helix bundle does not require the separation of loops 2 and 4 as recently proposed by others and (2) alpha-helices 3 and/or 4 are involved in the insertion of apoLp-III in both phospholipid bilayers and monolayers. The conformational flexibility of helices 3 and 4 is required for the lipid-binding activity of apoLp-III. (3) Interaction of helices 1 and/or 5 with the lipid surface is required to the formation of stable lipoprotein complexes of any kind.
Asunto(s)
Apolipoproteínas/química , Proteínas de Insectos/química , Lipoproteínas/química , Animales , Apolipoproteínas/genética , Apolipoproteínas/metabolismo , Cisteína/química , Cisteína/genética , Dimiristoilfosfatidilcolina/química , Dimiristoilfosfatidilcolina/metabolismo , Disulfuros/química , Saltamontes , Proteínas de Insectos/genética , Proteínas de Insectos/metabolismo , Lipoproteínas/metabolismo , Manduca , Micelas , Mutagénesis Sitio-Dirigida , Unión Proteica/genética , Conformación Proteica , Estructura Secundaria de Proteína/genética , Estructura Terciaria de Proteína/genética , UltracentrifugaciónRESUMEN
An original method for the study of the lipid binding properties of exchangeable apolipoproteins is reported. Binding of Locusta migratoria apolipophorin-III to Manduca sexta low-density lipophorin (LDLp) and high-density lipophorin (HDLp) was studied in vivo. This assay could be used useful to investigate the effect of mutations in the lipid binding properties of exchangeable apolipoproteins under physiological conditions.
Asunto(s)
Apolipoproteínas/metabolismo , Saltamontes , Lipoproteínas/metabolismo , Manduca , Animales , Apolipoproteínas/sangre , Apolipoproteínas/química , Sitios de Unión , Western Blotting , Electroforesis en Gel de Poliacrilamida , Lipoproteínas/sangre , Lipoproteínas/química , Lipoproteínas HDL/sangre , Lipoproteínas HDL/química , Lipoproteínas HDL/metabolismo , Lipoproteínas LDL/sangre , Lipoproteínas LDL/química , Lipoproteínas LDL/metabolismo , UltracentrifugaciónRESUMEN
Empyema of the lung is a very serious illness which must be detected quickly and treated aggressively. We report an unusual case of empyema of the lung associated with a boating accident while the patient was fishing in a sea loch off the west coast of Scotland.
Asunto(s)
Empiema/microbiología , Infecciones Estreptocócicas/microbiología , Antibacterianos/uso terapéutico , Tubos Torácicos , Empiema/diagnóstico por imagen , Empiema/etiología , Empiema/terapia , Humanos , Masculino , Persona de Mediana Edad , Ahogamiento Inminente/complicaciones , Radiografía , Serotipificación , Infecciones Estreptocócicas/diagnóstico por imagen , Infecciones Estreptocócicas/etiología , Infecciones Estreptocócicas/terapia , Streptococcus/clasificación , ToracostomíaRESUMEN
Plasminogen activator inhibitor type 1 (PAI-1), the primary physiologic inhibitor of plasminogen activation, is associated with the adhesive glycoprotein vitronectin (Vn) in plasma and the extracellular matrix. In this study we examined the binding of different conformational forms of PAI-1 to both native and urea-purified vitronectin using a solid-phase binding assay. These results demonstrate that active PAI-1 binds to urea-purified Vn with approximately 6-fold higher affinity than to native Vn. In contrast, inactive forms of PAI-1 (latent, elastase-cleaved, synthetic reactive center loop peptide-annealed, or complexed to plasminogen activators) display greatly reduced affinities for both forms of adsorbed Vn, with relative affinities reduced by more than 2 orders of magnitude. Structurally, these inactive conformations all differ from active PAI-1 by insertion of an additional strand into beta-sheet A, suggesting that it is the rearrangement of sheet A that results in reduced Vn affinity. This is supported by the observation that PAI-1 associated with beta-anhydrotrypsin, which does not undergo rearrangement of beta-sheet A, shows no such decrease in affinity, whereas PAI-1 complexed to beta-trypsin, which does undergo sheet A rearrangement, displays reduced affinity for Vn similar to PAI-1.plasminogen activator complexes. Together these data demonstrate that the interaction between PAI-1 and Vn depends on the conformational state of both proteins and suggest that the Vn binding site on PAI-1 is sensitive to structural changes associated with loss of inhibitory activity.
Asunto(s)
Inhibidor 1 de Activador Plasminogénico/metabolismo , Vitronectina/metabolismo , Hidrólisis , Inhibidor 1 de Activador Plasminogénico/química , Unión Proteica , Conformación ProteicaRESUMEN
One feature that distinguishes all of the inhibitory members of the serpin gene family is the presence of a small uncharged residue at the P14 position of the reactive center loop. In this report we examine the effects of mutations at this position, in the serpin, plasminogen activator inhibitor type 1 (PAI-1). Replacement of the native P14 Thr-333 residue by an Arg (Thr-333-->Arg) resulted in complete loss of inhibitory activity toward tissue-type plasminogen activator and urokinase-type plasminogen activator. Comparison of the binding of the mutant inhibitor and wild type PAI-1 (WTPAI-1) to anhydrotrypsin indicated that the initial interaction of the two inhibitors with proteases was identical. However, whereas WTPAI-1 forms SDS-stable complexes with both plasminogen activators, the mutant PAI-1 was efficiently cleaved as a substrate. Amino-terminal sequence analysis indicated that cleavage of the mutant PAI-1 occurred at its reactive center P1-P1' Arg-Met bond. Thermal denaturation studies of native and cleaved PAIs indicated that native Thr-333-->Arg mutant had a thermal stability identical to active WTPAI-1 and that both proteins became significantly more stable following cleavage by elastase (cleaved at the P4-P3 bond). Finally, the function of recombinant PAI-1 variants containing 15 of the possible 19 amino acid substitutions at P14 were analyzed. While residue size appeared to have little effect on inhibitory activity, the presence of either a positive or a negative charge at P14, converted PAI-1 to a substrate. Taken together, these results suggest that while insertion of the reactive center loop is not essential for protease binding, it is a necessary second step required for inhibitor function. The presence of a charged residue at P14 can retard this insertion, resulting in conversion of the serpin to a substrate.
Asunto(s)
Inhibidor 1 de Activador Plasminogénico/química , Serpinas/química , Secuencia de Bases , Sitios de Unión , Cartilla de ADN/química , Concentración de Iones de Hidrógeno , Técnicas In Vitro , Datos de Secuencia Molecular , Movimiento (Física) , Mutagénesis Sitio-Dirigida , Inhibidor 1 de Activador Plasminogénico/inmunología , Desnaturalización Proteica , Relación Estructura-Actividad , Especificidad por Sustrato , Activador de Plasminógeno de Tipo Uroquinasa/antagonistas & inhibidoresRESUMEN
Plasminogen activator inhibitor type 1 (PAI-1) is the rapid physiologic inhibitor of tissue-type plasminogen activator and urokinase-type plasminogen activator (uPA). In plasma and the extracellular matrix, PAI-1 is associated with the adhesive glycoprotein vitronectin. In order to characterize the PAI-1 structural domain responsible for binding to vitronectin, the segment of the PAI-1 cDNA encoding amino acids 13-147 (nucleotides 248-650) was randomly mutagenized and subcloned into a bacterial expression vector containing the mature PAI-1 coding sequence. Recombinant PAI-1 mutants were expressed in Escherichia coli and bacterial lysates assayed in duplicate for uPA inhibitory activity and vitronectin binding. Of 190 clones screened, six consistently demonstrated decreased vitronectin binding relative to uPA inhibitory activity. DNA sequence analysis of four of these clones identified 10 unique missense mutations, all located between base pairs 298 and 641, with each clone containing between one and four substitutions. Each substitution was expressed independently by site-directed mutagenesis and again analyzed for uPA inhibitory activity and vitronectin binding. Five point mutations that selectively disrupt vitronectin binding were identified. All 5 residues are located on the exterior of the PAI-1 structure. These findings appear to define a complex binding surface that bridges alpha-helices C and E to beta-strand 1A and includes amino acids 55, 109, 110, 116, and 123. These results suggest that vitronectin binding may stabilize the active conformation of PAI-1 by restricting the movement of beta-sheet A and thereby preventing insertion of the reactive center loop.
Asunto(s)
Glicoproteínas/metabolismo , Inhibidor 1 de Activador Plasminogénico/metabolismo , Secuencia de Aminoácidos , Secuencia de Bases , Sitios de Unión , Clonación Molecular , ADN Complementario , Escherichia coli/genética , Datos de Secuencia Molecular , Mutagénesis , Inhibidor 1 de Activador Plasminogénico/química , Inhibidor 1 de Activador Plasminogénico/genética , Mutación Puntual , Conformación Proteica , Análisis de Secuencia de ADN , VitronectinaRESUMEN
Plasminogen activator inhibitor 1 (PAI-1), a member of the serine protease inhibitor (Serpin) superfamily, is the primary inhibitor of the plasminogen activators tPA and uPA. PAI-1 is produced in an active form but converts to an inactive or latent form with a half-life of approximately 1 h at pH 7.5, 37 degrees C. This study describes the construction, expression, and characterization of PAI-1 mutants with increased functional stability. Three mutations that disrupt an ion pair, present in latent PAI-1, between Arg-30 and Glu-350 (P4'), were introduced into recombinant PAI-1. All three mutant proteins maintained normal functional activity against both uPA and tPA. However, the half-life of each purified PAI-1 mutant was extended compared to the 1.1 h observed for wild-type PAI-1 (wtPAI-1) (1.2 h for Glu-350-->Arg, 2.0 h for Glu-350-->Pro, and 2.1 h for the Arg-30-->Glu mutation). An additional PAI-1 variant containing a second mutation designed to potentially reconstitute the ion pair (Arg-30-->Glu, Glu-350-->Arg) failed to restore the wild-type half-life. Circular dichroism spectra analysis indicated that the active and latent forms of wtPAI-1 and all four mutants contained similar secondary structural elements. Thermal stability determinations showed that latent wtPAI-1 was much more structurally stable than the active conformation. However, the latent form for all four mutants was significantly less stable than the corresponding wtPAI-1 conformer. This is the first report of PAI-1 mutants which have been specifically engineered to produce enhanced functional stability.