Knock, knock, knocking on muscle doors. Visions of the transport of substrates across the plasma membrane in muscle

El múscul té un paper central en el metabolisme. Així, el múscul utilitza quantitats substancials de glucosa durant l'estat absortiu, i els canvis en la captació muscular de la glucosa provoquen alteracions en la utilització global de la glucosa per l'organisme sencer. El múscul constitueix també el principal reservori corporal d'aminoàcids i de proteïnes. A més, el metabolisme muscular és mantingut mitjantçant l'activitat de molts diferents transportadors localitzats a la membrana plasmàtica, com són els transportadors de glucosa, carnitina, creatina o aminoàcids; aquests transportadors capten o alliberen, a través de la membrana plasmàtica de la cèl·lula muscular, diferents substrats o metabòlits. L'objectiu d'aquesta revisió consisteix en la caracterització molecular de les principals proteïnes transportadores presents a la membrana plasmàtica de les cèl·lules musculars, així com l'anàlisi de les seves propietats reguladores.Muscle is a major player in metabolism. It uses large amounts of glucose in the absorptive state and changes in muscle insulin-stimulated glucose uptake alter whole-body glucose disposal. Lipid substrates such as fatty acids or ketone bodies are preferentially used by muscle in certain physiological conditions. Muscle is also the main reservoir of amino acids and protein. The activity of many different plasma membrane transporters such as glucose carriers, carnitine, creatine or amino acid transporters maintain muscle metabolism by taking up or releasing substrates or metabolites across the cell surface. The goal of this review is the molecular characterization of muscle membrane transporter proteins and the analysis of their regulatory roles

Nuevas investigaciones histórico-genealógicas referentes al M.R.P. Diego Laynez y su distinguida familia de Almazán y de Matute

Copia digital. Valladolid : Junta de Castilla y León. Consejería de Cultura y Turismo, 2009-201

Portal WEB 2.0. utilizando Framework Struts

El propósito de este proyecto es la implementación de un portal interactivo de contactos utilizando las tecnologías J2EE mediante Struts y siguiendo la tendencia Web 2.0. Previo a esta implementación se ha hecho una valoración del mercado actual de los portales de contactos y se han evaluado los servicios que ofrecen para posteriormente añadirlos a la demostración tecnológica. Tras esto se ha explicado lo que es la tendencia Web 2.0. Finalmente se han evaluado las diferentes opciones o tecnologías Web disponibles en la actualidad para la creación de un portal de este tipo.El propósito de este proyecto es la implementación de un portal interactivo de contactos utilizando las tecnologías J2EE mediante Struts y siguiendo la tendencia Web 2.0. Previo a esta implementación se ha hecho una valoración del mercado actual de los portales de contactos y se han evaluado los servicios que ofrecen para posteriormente añadirlos a la demostración tecnológica. Tras esto se ha explicado lo que es la tendencia Web 2.0. Finalmente se han evaluado las diferentes opciones o tecnologías Web disponibles en la actualidad para la creación de un portal de este tipo. Se pretende que el portal aporte diferentes servicios al usuario, entre los cuales destacan la búsqueda de pareja, la sección de noticias y un ránquing semanal/mensual con los usuarios más votados. Además de todos estos servicios, el portal ofrece la posibilidad de registrar a los usuarios y puede ser administrado mediante una cuenta de administrador. La implementación del sistema se ha realizado siguiendo el patrón de diseño MVC utilizando diferentes tecnologías como son XML, el lenguaje de programación Java en su especificación J2EE y el Framework Struts. Las páginas Web (vista) se han realizado mediante JSP’s aplicándoles CSS y la utilización de JavaScript y AJAX en ciertas partes. El controlador y la lógica de negocio (modelo) se implementa con Struts. Como base de datos se utiliza MySQL (fácil y simple de administrar además de tener coste 0). La intención es que la aplicación se sostenga sobre dos contenedores: el Web Apache HTTP y el de aplicaciones Apache Tomcat, ambos gratuitos. El sistema requiere de seguridad en ciertas partes como son el registro y el login de usuarios para lo cual se utiliza el protocolo SSL gracias a una extensión de Struts llamada SSLEXT

Membrane protein stabilization strategies for structural and functional studies

Accounting for nearly two-thirds of known druggable targets, membrane proteins are highly relevant for cell physiology and pharmacology. In this regard, the structural determination of pharmacologically relevant targets would facilitate the intelligent design of new drugs. The structural biology of membrane proteins is a field experiencing significant growth as a result of the development of new strategies for structure determination. However, membrane protein preparation for structural studies continues to be a limiting step in many cases due to the inherent instability of these molecules in non-native membrane environments. This review describes the approaches that have been developed to improve membrane protein stability. Membrane protein mutagenesis, detergent selection, lipid membrane mimics, antibodies, and ligands are described in this review as approaches to facilitate the production of purified and stable membrane proteins of interest for structural and functional studies

Ex vivo revascularization in liver bioengineering. A critical first step towards effective transplantation of bioengineered livers.

Hasta la fecha, el trasplante de hígado es la única opción disponible para pacientes con enfermedad hepática terminal. El problema es la gran falta de órganos para trasplante. Por lo tanto, nuevas terapias emergentes, como la medicina regenerativa y la bioingeniería de órganos, esperan resolver este problema de escasez. Sin embargo, hasta la fecha nadie ha podido generar hígados de bioingeniería que puedan ser trasplantados con éxito, debido a la falta de permeabilidad vascular lo que conduce a trombosis en el animal receptor. Por lo tanto, el objetivo principal de esta tesis era el de generar una vasculatura ensamblada in vitro que fuera estable y funcional. Paralelamente, también hemos trabajado en la creación de un modelo animal de regeneración hepática, en el que las piezas de bioingeniería revascularizadas pueden ser trasplantados. Además, en colaboración con el grupo de investigación del Dr. Bart Spee y del Dr. Hans Clevers de la Universidad de Utrecht, probamos a sembrar hepatocitos derivados de células somáticas y células madre hepáticas adultas Lgr5 + en ECM descelularizada hepática, mejorando su destino y función hepática cuando se siembran en estos scaffolds. Esto puede permitir la posibilidad de obtener una fuente de células hepáticas que se puede expandir para obtener los grandes números requeridos para la bioingeniería de órganos, aumentando la complejidad estructural y anatómica de nuestros hígados de bioingeniería. En resumen, estos resultados pueden proporcionar las herramientas necesarias (una vasculatura funcional estable, una nueva fuente de hepatocitos y un modelo animal para trasplante) para generar hígados de bioingeniería adecuados para su futura traslación a la clínica.To date, liver transplantation is the only available option for patients with terminal liver disease. The problem is the huge lack of organs for transplantation. Therefore, new emerging therapies such as regenerative medicine and organ bioengineering present hope to solve this problem of organ shortage. However, to date no one has been able to generate bioengineered livers that can successfully be transplanted, due to lack of vascular patency in these bioengineered organs, leading to thrombosis in the receptor animal. Thus, the main objective of this thesis was to generate an in vitro assembled vasculature that was stable and functional. In parallel, we have also worked on the creation of an animal model of liver regeneration, in which the revascularized bioengineering grafts can be transplanted. In addition, in collaboration with the research group of Dr. Bart Spee and Dr. Hans Clevers from the University of Utrecht, we tested seeding hepatocytes derived from somatic cells and Lgr5+ adult liver stem cells in liver decellularized ECM, enhancing their hepatic fate and function when seeded in these scaffolds. This may allow the possibility of obtaining a source of hepatic cells which can be expanded into the large numbers required for organ bioengineering, increasing the structural and anatomical complexity of our bioengineering livers. In summary, these results can provide the necessary tools (stable functional vasculature, a novel source of hepatocytes and an animal model for transplantation) to generate bioengineered livers suitable for future translation into the clinic.<br /

The Ectodomains of rBAT and 4F2hc Are Fake or Orphan α-Glucosidases

It is known that 4F2hc and rBAT are the heavy subunits of the heteromeric amino acid transporters (HATs). These heavy subunits are N-glycosylated proteins, with an N-terminal domain, one transmembrane domain and a bulky extracellular domain (ectodomain) that belongs to the α-amylase family. The heavy subunits are covalently linked to a light subunit from the SLC7 family, which is responsible for the amino acid transport activity, forming a heterodimer. The functions of 4F2hc and rBAT are related mainly to the stability and trafficking of the HATs in the plasma membrane of vertebrates, where they exert the transport activity. Moreover, 4F2hc is a modulator of integrin signaling, has a role in cell fusion and it is overexpressed in some types of cancers. On the other hand, some mutations in rBAT are found to cause the malfunctioning of the b0,+ transport system, leading to cystinuria. The ectodomains of 4F2hc and rBAT share both sequence and structure homology with α-amylase family members. Very recently, cryo-EM has revealed the structure of several HATs, including the ectodomains of rBAT and 4F2hc. Here, we analyze available data on the ectodomains of rBAT and 4Fhc and their relationship with the α-amylase family. The physiological relevance of this relationship remains largely unknown. Keywords: N-glycosylation; SLC3; alpha-amylase; alpha-glucosidase; ancillary protein; ectodomain; scaffold protein; structure; transporter

From general research questions to specific answers: Underspecificity as a source of uncertainty in biological conservation

P. 167-180Species distribution modelling may support ecologists in conservation decision-making. However, the applicability of management recommendations depends on the uncertainty associated to the modelling process. A key source of uncertainty is the underspecificity of the research question. Modelling specific questions is straightforward since they drive clearly the methodological choices about input data and model building. Nevertheless, when the research questions remain underspecific, modellers must choose among a wide spectrum of choices, with each decision sequence driving to a different outcome that explain partially the target question. We show how the underspecificity associated to a general research question about Great Bustard breeding success at geographic scale drives to multiple decision choices, leads to a variety of model outcomes and hampers the identification of specific conservation actions. We ran generalised linear models using multi-model inference on a set of databases built according to specific sequences of methodological choices. Then, we evaluated variations in model performance, complexity (parsimony) and nature of predictors, as well as averaged model predictions and spatial congruence among model outputs. Deviance and parsimony varied widely (11.46% to 83.33% and 7 to 18, respectively), as did model averaged mean predictions in occupied areas, contributing predictors and spatial congruence among outputs (rPearson = 0.44 ± 0.23 for models calibrated in occupied areas; 0.48 ± 0.06 for models calibrated in potential/accessible areas). We recommend to carefully fix research questions and associated methodological options through collaborative working frameworks to conceptualize modelling approaches and, thus, to mitigate problems arising from underspecificity and other forms of uncertainty in conservation applications.S

Rush hour of LATs towards their transport cycle

The mammalian SLC7 family comprises the L-amino acid transporters (LATs) and the cationic amino acid transporters (CATs). The relevance of these transporters is highlighted by their involvement in several human pathologies, including inherited rare diseases and acquired diseases, such as cancer. In the last four years, several crystal or cryo-EM structures of LATs and CATs have been solved. These structures have started to fill our knowledge gap that previously was based on the structural biology of remote homologs of the amino acid-polyamine-organocation (APC) transporters. This review recovers this structural and functional information to start generating the molecular bases of the transport cycle of LATs. Special attention is given to the known transporter conformations within the transport cycle and the molecular bases for substrate interaction and translocation, including the asymmetric interaction of substrates at both sides of the plasma membrane. Keywords: APC; LATs; SLC7; transport cycle; structure; substrate binding; substrate translocatio

Phosphatidylinositol 3-Kinase inhibitors block differentiation of skeletal muscle cells

Skeletal muscle differentiation involves myoblast alignment, elongation, and fusion into multinucleate myotubes, together with the induction of regulatory and structural muscle-specific genes. Here we show that two phosphatidylinositol 3-kinase inhibitors, LY294002 and wortmannin, blocked an essential step in the differentiation of two skeletal muscle cell models. Both inhibitors abolished the capacity of L6E9 myoblasts to form myotubes, without affecting myoblast proliferation, elongation, or alignment. Myogenic events like the induction of myogenin and of glucose carrier GLUT4 were also blocked and myoblasts could not exit the cell cycle, as measured by the lack of mRNA induction of p21 cyclin-dependent kinase inhibitor. Overexpresssion of MyoD in 10T1/2 cells was not sufficient to bypass the myogenic differentiation blockade by LY294002. Upon serum withdrawal, 10T1/2-MyoD cells formed myotubes and showed increased levels of myogenin and p21. In contrast, LY294002-treated cells exhibited none of these myogenic characteristics and maintained high levels of Id, a negative regulator of myogenesis. These data indicate that whereas phosphatidylinositol 3-kinase is not indispensable for cell proliferation or in the initial events of myoblast differentiation, i.e. elongation and alignment, it appears to be essential for terminal differentiation of muscle cells