Viroporins: structure and biological functions.

Viroporins are small, hydrophobic proteins that are encoded by a wide range of clinically relevant animal viruses. When these proteins oligomerize in host cell membranes, they form hydrophilic pores that disrupt a number of physiological properties of the cell. Viroporins are crucial for viral pathogenicity owing to their involvement in several diverse steps of the viral life cycle. Thus, these viral proteins, which include influenza A virus matrix protein 2 (M2), HIV-1 viral protein U (Vpu) and hepatitis C virus p7, represent ideal targets for therapeutic intervention, and several compounds that block their pore-forming activity have been identified. Here, we review recent studies in the field that have advanced our knowledge of the structure and function of this expanding family of viral proteins.

Membrane integration of poliovirus 2B viroporin.

Virus infections can result in a variety of cellular injuries, and these often involve the permeabilization of host membranes by viral proteins of the viroporin family. Prototypical viroporin 2B is responsible for the alterations in host cell membrane permeability that take place in enterovirus-infected cells. 2B protein can be localized at the endoplasmic reticulum (ER) and the Golgi complex, inducing membrane remodeling and the blockade of glycoprotein trafficking. These findings suggest that 2B has the potential to integrate into the ER membrane, but specific information regarding its biogenesis and mechanism of membrane insertion is lacking. Here, we report experimental results of in vitro translation-glycosylation compatible with the translocon-mediated insertion of the 2B product into the ER membrane as a double-spanning integral membrane protein with an N-/C-terminal cytoplasmic orientation. A similar topology was found when 2B was synthesized in cultured cells. In addition, the in vitro translation of several truncated versions of the 2B protein suggests that the two hydrophobic regions cooperate to insert into the ER-derived microsomal membranes.

Comparison of mortality due to severe multiple trauma in two comprehensive models of emergency care: Atlantic Pyrenees (France) and Navarra (Spain).

BACKGROUND: Injury due to external causes is an important health problem in our society today. Emergency care systems based on the concept of "comprehensive care" can prevent deaths and disabilities as well as limit the severity and pain caused by trauma. OBJECTIVE: To investigate the frequency and characteristics of different mechanisms of injury and to estimate mortality, comparing two comprehensive emergency systems: Atlantic Pyrenees (AP) in France and Navarra (NA) in Spain. MATERIAL AND METHODS: A prospective cohort study of severe multiple-injury patients attended to by the comprehensive emergency care systems of AP and NA from April 1, 2001 to March 31, 2002. Data were collected from personal patient data, the emergency coordination center "112," pre-hospital and hospital health care levels, and discharge data. Bivariate statistical analysis and multivariate logistic regression models were employed for statistical management. RESULTS: There were 614 severe multiple trauma patients recorded, 278 in AP and 336 in NA. Significant differences were observed in arrival time, pre-hospitalization care, pre-hospital Revised Trauma Score (RTS), Injury Severity Score (ISS) at the intensive care unit, and procedures used (intubation, administration of fluids, immobilization, and diagnostic methods). Logistic regression showed significant differences in patient death, age (odds ratio [OR] 1.02, 95% confidence interval [CI] 1.01-1.03), penetrating or accidental injuries, (OR 3.85, 95% CI 1.1-13.1), RTS (OR 0.58, 95% CI 0.5-0.7), and ISS score (OR 1.05, 95% CI 1.0-1.1). CONCLUSION: Despite a more aggressive approach and employment of greater resources, the French comprehensive trauma system does not show greater survival rates among injured patients compared to Navarra, even when controlling for confounding factors like age, injury mechanism, RTS, ISS, and others.

[Intracranial pressure response during secretion aspiration after administration of a muscle relaxant]. / Respuesta de la presión intracraneal durante la aspiración de secreciones previa administración de un relajante muscular.

UNLABELLED: Aspiration of secretions is a usual nursing technique in patients undergoing mechanical ventilation that may be the cause of increased Intracranial Pressure (ICP). OBJECTIVE: This study aims to evaluate the repercussion of a muscle relaxant on ICP with secretion aspiration. METHOD: Clinical trial using the same patient as case and control, performing two endotracheal aspirations in each patients, on of them after administration of a muscle relaxant (Cis-Atracurium) and another no. The bolus administration of the relaxant in the first or second aspiration was done randomly. Thirteen patients with intraparenchymatous ICP measurement catheter were studied within the first 36 hours post-placement and with sedoanalgesia for a score of 6 on the Ramsay scale. ICP and CPP were measured before, during and after each aspiration. STATISTICAL METHOD: SPSS 11.0 program was used. Data analysis by Student's t test for paired data. Statistical significance level accepted was 95%. RESULTS: On comparing the cases in which muscle relaxant was administered with those in which it was not administered, statistically significant differences were found in the ICP and CCP values during secretion aspiration. CONCLUSIONS: According to the data obtained in the study, a lower increase of ICP was observed during secretion aspiration in those cases in which muscle relaxant was administered prior to the aspiration.

Respuesta de la presión intracraneal durante la aspiración de secreciones previa administración de un relajante muscular / Intracranial pressure response during secretion aspiration after administration of a muscle relaxant

La aspiración de secreciones es una técnica de enfermería habitual en los pacientes sometidos a ventilación mecánica, que puede ser causa de elevación de la presión intracraneal (PIC). Objetivo: El objetivo del estudio es valorar la repercusión de un relajante muscular sobre la PIC ante la aspiración de secreciones. Material y métodos: Ensayo clínico que tomaba al mismo paciente como caso y control, se realizaron 2 aspiraciones endotraqueales a cada paciente, una de ellas previa a la administración de un relajante muscular (cisatracurio) y otra no. La administración en bolo del relajante en la primera o segunda aspiración se realizó de forma aleatoria. Se estudiaron 13 pacientes portadores de catéter de medición de PIC intraparenquimatoso dentro de las primeras 36 h poscolocación y sedoanalgesiados para una puntuación de 6 en la escala de Ramsay. Se midió la PIC y la presión de perfusión cerebral (PPC) antes, durante y después de cada aspiración. Metodología estadística: se utilizó el programa SPSS 11.0. Análisis de datos mediante la t de Student para datos apareados. El nivel de significación estadística aceptado fue del 95%. Resultados: Al comparar los casos en los que se administró relajante muscular con los que no se administró, se encontraron diferencias significativas en los valores de PIC y PPC durante la aspiración de secreciones. Conclusiones: Según los datos obtenidos en el estudio, se ha observado menor aumento de la PIC durante la aspiración de secreciones en los casos en los que se administró el relajante muscular previo a la aspiración

Aspiration of secretions is a usual nursing technique in patients undergoing mechanical ventilation that may be the cause of increased Intracranial Pressure (ICP). Objective: This study aims to evaluate the repercussion of a muscle relaxant on ICP with secretion aspiration. Method: Clinical trial using the same patient as case and control, performing two endotracheal aspirations in each patients, on of them after administration of a muscle relaxant (Cis-Atracurium) and another no. The bolus administration of the relaxant in the first or second aspiration was done randomly. Thirteen patients with intraparenchymatous ICP measurement catheter were studied within the first 36 hours post-placement and with sedoanalgesia for a score of 6 on the Ramsay scale. ICP and CPP were measured before, during and after each aspiration. Statistical method: SPSS 11.0 program was used. Data analysis by Student's t test for paired data. Statistical significance level accepted was 95%. Results: On comparing the cases in which muscle relaxant was administered with those in which it was not administered, statistically significant differences were found in the ICP and CCP values during secretion aspiration. Conclusions: According to the data obtained in the study, a lower increase of ICP was observed during secretion aspiration in those cases in which muscle relaxant was administered prior to the aspiration

Interfacial domains in Sindbis virus 6K protein. Detection and functional characterization.

Alphavirus 6K is a short, constitutive membrane protein involved in virus glycoprotein processing, membrane permeabilization, and the budding of virus particles. The amino-terminal region that immediately precedes the transmembrane anchor contains a conserved sequence motif consisting of two interfacial domains separated by Asn and Gln residues. The presence of this motif confers on the 6K pretransmembrane region the tendency to partition into the membrane interface. To study the functional importance of the interfacial sequences, three different Sindbis virus 6K variants were obtained with the following modifications: 9YLW11xAAA, 18FWV20xAAA, and 9YLW11xAAA/18FWV20xAAA. Reconstituted mutant viruses were infectious and showed no defects in glycoprotein processing, although virus budding was hampered. Single 6K expression in Escherichia coli cells showed interfacial mutants to have a diminished capacity to modify membrane permeability and to have lower toxicity. In particular, the 9YLW11xAAA/18FWV20xAAA variant was expressed at high levels and did not enhance membrane permeability significantly, although it retained its integral membrane protein condition. Parallel analyses of membrane permeabilization in baby hamster kidney cells were carried out using a Sindbis virus replicon that synthesized both capsid protein and 6K. Transfection of the construct with wild-type 6K strongly increased permeability to the antibiotic hygromycin B. Replicons encoding 6K interfacial mutants induced lower membrane permeabilization. Again, the greatest impairment was observed for the 9YLW11xAAA/18FWV20xAAA variant, permeabilization activity of which was approximately 10% that of wild-type 6K. These findings show the importance of the interfacial 6K sequence for virus budding and modification of membrane permeability.