The role of protein denaturation energetics and molecular chaperones in the aggregation and mistargeting of mutants causing primary hyperoxaluria type I.

Primary hyperoxaluria type I (PH1) is a conformational disease which result in the loss of alanine:glyoxylate aminotransferase (AGT) function. The study of AGT has important implications for protein folding and trafficking because PH1 mutants may cause protein aggregation and mitochondrial mistargeting. We herein describe a multidisciplinary study aimed to understand the molecular basis of protein aggregation and mistargeting in PH1 by studying twelve AGT variants. Expression studies in cell cultures reveal strong protein folding defects in PH1 causing mutants leading to enhanced aggregation, and in two cases, mitochondrial mistargeting. Immunoprecipitation studies in a cell-free system reveal that most mutants enhance the interactions with Hsc70 chaperones along their folding process, while in vitro binding experiments show no changes in the interaction of folded AGT dimers with the peroxisomal receptor Pex5p. Thermal denaturation studies by calorimetry support that PH1 causing mutants often kinetically destabilize the folded apo-protein through significant changes in the denaturation free energy barrier, whereas coenzyme binding overcomes this destabilization. Modeling of the mutations on a 1.9 Å crystal structure suggests that PH1 causing mutants perturb locally the native structure. Our work support that a misbalance between denaturation energetics and interactions with chaperones underlie aggregation and mistargeting in PH1, suggesting that native state stabilizers and protein homeostasis modulators are potential drugs to restore the complex and delicate balance of AGT protein homeostasis in PH1.

Primary hyperoxaluria in a compound heterozygote infant.

BACKGROUND: Primary hyperoxaluria type 1 is a rare disorder caused by a defect in the hepatic metabolism of glyoxylate. Cases presenting in infancy are very uncommon and often have a severe course leading to early end-stage renal failure. METHODS: We treated a case of early presentation of primary hyperoxaluria type 1 and reviewed the relevant literature. RESULTS: A 4-month-old female infant was admitted to our hospital because of acute renal failure and nephrocalcinosis. Mutational analysis of alanine-glyoxylate aminotransferase gene revealed compound heterozygosity in the infant, confirming the development of primary hyperoxaluria type 1. A few weeks later, the condition of the infant worsened during an interdialytic period and died. CONCLUSIONS: Interest of this case is based on the coexistence of two mutations of alanine-glyoxylate aminotransferase gene recently reported, and it confirms the severe course of the disease when it presents in infancy. It also highlights the importance of the association of nephrocalcinosis and urolithiasis as key diagnostic manifestations of primary hyperoxaluria type 1.

Estudio del primer brote por Enterococcus faecium vanA en Canarias / Study ofthefirstoutbreakof vanA enterococcus faecium in thecanaryislands

Introducción En julio de 2005 se aisló el primer Enterococcus faecium resistente a vancomicina (EFRV) genotipo vanA en el Hospital Universitario de Canarias en un paciente trasplantado renal ingresado en la Unidad de Nefrología. En los meses siguientes se aisló EFVR en otros 15 pacientes trasplantados renales ingresados en la misma unidad. Nuestro objetivo fue estudiar este primer brote de EFVR vanA en el Hospital Universitario de Canarias y el vínculo epidemiológico con los aislamientos de EFVR vanA encontrados también en otros 2 hospitales universitarios ubicados en las Islas Canarias. Material y métodos Se estudiaron mediante métodos microbiológicos y moleculares un total de 22 aislamientos de EFRV y las historias clínicas de los 22 pacientes de los que se aislaron. Resultados y conclusiones e confirmó mediante electroforesis de campo pulsante que los aislamientos del brote pertenecían a una misma clona y, a su vez, se confirmó el vínculo epidemiológico con los primeros aislamientos en los otros 2 hospitales universitarios relacionando los resultados moleculares con los datos epidemiológicos. Todos los aislamientos pertenecían a la secuencia tipo ST18 mediante multilocus sequence typing, asociado al complejo clonal 17. El complejo clonal 17 es un linaje que comprende una población policlonal que se ha adaptado bien al ambiente hospitalario y que se aísla en los 5 continentes (AU)

Introduction In July, 2005 the first vancomycin-resistant Enterococcus faecium (VREF) with a genotype vanA was isolated in Hospital Universitario de Canarias (HUC). From September to December 2005, VREF vanA was isolated from another 15 patients (3 nosocomial infections and 12 rectal carriers). All of them were kidney transplant patients hospitalized in the Nephrology ward. This study describes the first VREF vanA outbreak in the HUC and the epidemiological link of the first VREF vanA isolates found in another two university hospitals in the Canary Islands. Materials and methods We studied a total of 22 VREF isolates by microbiological and molecular methods. Epidemiological and clinical data of the patients involved were collected. Results and conclusions We confirmed that these VREF isolates belonged to the same clone using pulse-field gel electrophoresis (PFGE). In November 2005 and February 2006, the first VREF were isolated in two other University Hospitals in the Canary Islands and we also confirmed the link with the HUC cluster by comparison of patient-related information with the molecular typing data. These VREF isolates belonged to the ST18 associated to the Clonal Complex-17 (CC17). CC17 is the major hospital adapted lineage, representing a polyclonal population and associated to VREF outbreaks and infections in the five continents (AU)

[Study of the first outbreak of vanA enterococcus faecium in the Canary Islands]. / Estudio del primer brote por Enterococcus faecium vanA en Canarias.

INTRODUCTION: In July, 2005 the first vancomycin-resistant Enterococcus faecium (VREF) with a genotype vanA was isolated in Hospital Universitario de Canarias (HUC). From September to December 2005, VREF vanA was isolated from another 15 patients (3 nosocomial infections and 12 rectal carriers). All of them were kidney transplant patients hospitalized in the Nephrology ward. This study describes the first VREF vanA outbreak in the HUC and the epidemiological link of the first VREF vanA isolates found in another two university hospitals in the Canary Islands. MATERIALS AND METHODS: We studied a total of 22 VREF isolates by microbiological and molecular methods. Epidemiological and clinical data of the patients involved were collected. RESULTS AND CONCLUSIONS: We confirmed that these VREF isolates belonged to the same clone using pulse-field gel electrophoresis (PFGE). In November 2005 and February 2006, the first VREF were isolated in two other University Hospitals in the Canary Islands and we also confirmed the link with the HUC cluster by comparison of patient-related information with the molecular typing data. These VREF isolates belonged to the ST18 associated to the Clonal Complex-17 (CC17). CC17 is the major hospital adapted lineage, representing a polyclonal population and associated to VREF outbreaks and infections in the five continents.

Postoperative bleeding in cardiac surgery: the role of tranexamic acid in patients homozygous for the 5G polymorphism of the plasminogen activator inhibitor-1 gene.

BACKGROUND: Plasminogen activator inhibitor 1 (PAI-1) attenuates the conversion of plasminogen to plasmin. Polymorphisms of the PAI-1 gene are associated with varying PAI-1 levels and risk of prothrombotic events in nonsurgical patients. The purpose of this study, a secondary analysis of a clinical trial, was to investigate whether PAI-1 genotype affects the efficacy of tranexamic acid (TA) in reducing postoperative chest tube blood loss of patients undergoing cardiopulmonary bypass. METHODS: Fifty patients were classified according to PAI-1 genotype (4G/4G, 4G/5G, or 5G/5G). Twenty-four received 2 g TA before and after cardiopulmonary bypass, whereas 26 received placebo. The authors recorded data related to coagulation, fibrinolysis, and bleeding before surgery, at admission to the intensive care unit (0 h), and 4 and 24 h later. RESULTS: In patients not receiving TA, those with the 5G/5G genotype had significantly higher chest tube blood loss and transfusion requirements compared with patients with the other genotypes at all time points. Patients with the 5G/5G genotype receiving TA showed significantly lower blood loss compared with the placebo group. There were no significant differences in blood loss or transfusion requirements between patients with the 4G/4G genotype when TA was used. CONCLUSIONS: Plasminogen activator inhibitor-1 5G/5G homozygotes who did not receive TA showed significantly greater postoperative bleeding than patients with other PAI-1 genotypes. 5G/5G homozygotes who received TA showed the greatest blood-sparing benefit.

[Primary hiperoxaluria: a new mutation in gen AGXT (R197Q) cause of neonatal convulsions]. / Hiperoxaluria primaria: una nueva mutación en el gen AGXT (r197q) causante de convulsiones neonatales.

Primary hyperoxaluria is a congenital innate error of the metabolism of the amino acids, that is transmitted like an autosomal recessive character. Two types of hyperoxaluria exist: the primary type I, that corresponds to the peroxisomal enzymatic deficit of the alanine glyoxylate aminotransferase in the liver (AGT) and type II, due to the deficit of the glyoxylate reductase/hydroxypyruvate reductase deficiency (GRHPR). The primary type I (AGT) is the most frequenty. We report the case of a female infant of one month of age, that on her first day post birth, presented myoclonic convulsions and tonic spasms, both during wakefullness and sleep periods, that became more frequent and did not respond to the use of anticonvulsants. The ictal Electroencephalogram presented an intermittent activity of spikes and spike-waves of high voltage in the right hemisphere. Eight minutes after the intravenous administration of 150 mg of pyridoxine, it was observed a diminution of the epileptic activity, as well as the clinical manifestations. The determination of organic acids in urine revealed an increase in the concentration levels of oxalic acid (3064 mmol/mol of creatinine). The molecular genetic study of the AGXT gene, showed the existence of a R197Q mutation in exón 5 of the patient and her father. She received treatment with pyridoxine at a dose of 50 mg/day. When she reached the age of three months both a normal electroencephalogram and biochemistry were obtained. Although it is a rare cause of neonatal convulsions, hyperoxaluria, due to new mutations is an underdiagnosed disease by neonatologists and paediatricias.