Regulation of cardiovascular connexins by mechanical forces and junctions

Connexins form a family of transmembrane proteins that consists of 20 members in humans and 21 members in mice. Six connexins assemble into a connexon that can function as a hemichannel or connexon that can dock to a connexon expressed by a neighbouring cell, thereby forming a gap junction channel. Such intercellular channels synchronize responses in multicellular organisms through direct exchange of ions, small metabolites, and other second messenger molecules between the cytoplasms of adjacent cells. Multiple connexins are expressed in the cardiovascular system. These connexins not only experience the different biomechanical forces within this system, but may also act as effector proteins in co-ordinating responses within groups of cells towards these forces. This review discusses recent insights regarding regulation of cardiovascular connexins by mechanical forces and junctions. It specifically addresses effects of (i) shear stress on endothelial connexins, (ii) hypertension on vascular connexins, and (iii) changes in afterload and the composition of myocardial mechanical junctions on cardiac connexin

Protein⁻Protein Interactions with Connexin 43: Regulation and Function

Connexins are integral membrane building blocks that form gap junctions, enabling direct cytoplasmic exchange of ions and low-molecular-mass metabolites between adjacent cells. In the heart, gap junctions mediate the propagation of cardiac action potentials and the maintenance of a regular beating rhythm. A number of connexin interacting proteins have been described and are known gap junction regulators either through direct effects (e.g., kinases) or the formation of larger multifunctional complexes (e.g., cytoskeleton scaffold proteins). Most connexin partners can be categorized as either proteins promoting coupling by stimulating forward trafficking and channel opening or inhibiting coupling by inducing channel closure, internalization, and degradation. While some interactions have only been implied through co-localization using immunohistochemistry, others have been confirmed by biophysical methods that allow detection of a direct interaction. Our understanding of these interactions is, by far, most well developed for connexin 43 (Cx43) and the scope of this review is to summarize our current knowledge of their functional and regulatory roles. The significance of these interactions is further exemplified by demonstrating their importance at the intercalated disc, a major hub for Cx43 regulation and Cx43 mediated effects

Ordered Assembly of the Adhesive and Electrochemical Connections within Newly Formed Intercalated Disks in Primary Cultures of Adult Rat Cardiomyocytes

The intercalated disk (ID) is a complex structure that electromechanically couples adjoining cardiac myocytes into a functional syncitium. The integrity of the disk is essential for normal cardiac function, but how the diverse elements are assembled into a fully integrated structure is not well understood. In this study, we examined the assembly of new IDs in primary cultures of adult rat cardiac myocytes. From 2 to 5 days after dissociation, the cells flatten and spread, establishing new cell-cell contacts in a manner that recapitulates the in vivo processes that occur during heart development and myocardial remodeling. As cells make contact with their neighbors, transmembrane adhesion proteins localize along the line of apposition, concentrating at the sites of membrane attachment of the terminal sarcomeres. Cx43 gap junctions and ankyrin-G, an essential cytoskeletal component of voltage gated sodium channel complexes, were secondarily recruited to membrane domains involved in cell-cell contacts. The consistent order of the assembly process suggests that there are specific scaffolding requirements for integration of the mechanical and electrochemical elements of the disk. Defining the relationships that are the foundation of disk assembly has important implications for understanding the mechanical dysfunction and cardiac arrhythmias that accompany alterations of ID architecture

A representação das deputadas parlamentares na imprensa

Conferência final do projeto "Política no Feminino: Políticas de género e estratégias de visibilidade das deputadas parlamentares". Trata-se de um projeto de investigação de âmbito académico, financiado pela FCT, integrando uma equipa multidisciplinar e internacional com o objetivo de sistematizar a representatividade e o perfil das mulheres na Assembleia da República a partir de 1975 até à atualidade. Outro dos objetivos consistiu em analisar a presença das parlamentares nos media e compreender as respectivas estratégias de visibilidade no espaço público através da mediação dos jornalistas. A conferência reuniu especialistas nas diversas áreas incluídas na investigação, nomeadamente estudos dos media e do jornalismo, ciência política e sociologia da comunicação, bem como jornalistas, deputados, investigadores, docentes e estudantes destas áreas

Effect of Charge Substitutions at Residue His-142 on Voltage Gating of Connexin43 Channels

AbstractPrevious studies indicate that the carboxyl terminal of connexin43 (Cx43CT) is involved in fast transjunctional voltage gating. Separate studies support the notion of an intramolecular association between Cx43CT and a region of the cytoplasmic loop (amino acids 119–144; referred to as “L2”). Structural analysis of L2 shows two α-helical domains, each with a histidine residue in its sequence (H126 and H142). Here, we determined the effect of H142 replacement by lysine, alanine, and glutamate on the voltage gating of Cx43 channels. Mutation H142E led to a significant reduction in the frequency of occurrence of the residual state and a prolongation of dwell open time. Macroscopically, there was a large reduction in the fast component of voltage gating. These results resembled those observed for a mutant lacking the carboxyl terminal (CT) domain. NMR experiments showed that mutation H142E significantly decreased the Cx43CT-L2 interaction and disrupted the secondary structure of L2. Overall, our data support the hypothesis that fast voltage gating involves an intramolecular particle-receptor interaction between CT and L2. Some of the structural constrains of fast voltage gating may be shared with those involved in the chemical gating of Cx43

Adaptability and stability of early sugarcane genotypes in Rio Grande do Sul, Brazil

O objetivo deste trabalho foi avaliar a adaptabilidade e estabilidade de genótipos de cana‑de‑açúcar de maturação precoce, quanto à produtividade de colmos e de Brix, no Estado do Rio Grande do Sul. Quinze genótipos de maturação precoce foram avaliados nas safras 2009/2010 e 2010/2011, por meio da análise de efeitos principais aditivos e interações multiplicativas (AMMI). As interações genótipo x ambiente foram de alta significância e evidenciaram a alteração de posição na classificação dos genótipos de um ambiente para outro. Novos genótipos superaram, em produtividade e estabilidade, o genótipo‑padrão precoce RB855156, embora este ainda se destaque pela produtividade, estabilidade moderada e ampla adaptabilidade. O genótipo RB966928 destacou-se pela riqueza e produtividade de Brix, estabilidade moderada e ampla adaptabilidade. Salto do Jacuí, RS, é o ambiente mais indicado para testes preliminares de seleção de genótipos.The objective of this work was to evaluate the adaptability and stability of early maturation sugarcane genotypes, as to yield of stalk and Brix, in Rio Grande do Sul state, Brazil. Fifteen early‑maturing genotypes were evaluated in the 2009/2010 and 2010/2011 seasons, through the additive main effects and multiplicative interaction (AMMI) analysis. Genotype x environment interactions were highly significant and evidenced changes in the genotype ranking according to the environment. New genotypes exceeded the standard early genotype RB855156 for productivity and stability, although it still stands out for its high productivity, moderate stability and wide adaptability. Genotype RB966928 stood out for its richness and yield of Brix, moderate stability and wide adaptability. Salto do Jacuí, RS, Brazil, is the most suitable site for preliminary tests of genotype selection

Rendimento de grãos de genótipos de mamona, semeados em três épocas, no Planalto Catarinense

The castor-bean (Ricinus communis L.) is a species with high oil production potential. Consequently, it is a very important crop for the Brazilian Program for Biodiesel. The objective of this study was to evaluate the agronomic performance of castor bean genotypes, at different sowing dates, in the plateau of Santa Catarina State, southern Brazil. The experiment was set in the city of Lages, during the growing season of 2006/07. Three sowing dates were tested: 11/03, 11/ 23 and 12/13. A split-plot randomized block was used as experimental design, with two replications per treatment. The following traits were evaluated: vegetative cycle, total cycle, plant height, first insertion raceme height, colon diameter, relationship seed-hulls, mass of a thousand seeds and grain yield. The interaction between genotype and sowing date affected vegetative cycle, total cycle and first insertion raceme height. Grain yield of all tested genotypes decreased with the delay in sowing date. The highest grain yield (1,500 kg ha-1) was obtained when sowing was performed in the beginning of November. Further studies, including new genotypes and a wider range of sowing dates, are necessary to determine the best castor bean sowing period in the high lands of Santa Catarina.A mamona (Ricinus communis L.) é uma espécie com alto potencial oleífero. Em função disto, é uma das culturas mais importantes no Programa Nacional de Biodiesel. O objetivo deste trabalho foi avaliar o comportamento de genótipos de mamona semeados em três épocas, quanto ao rendimento de grãos e características agronômicas. A semeadura foi realizada a campo, em 03/11, 23/11 e 13/12 de 2006. O ensaio foi implantado no delineamento experimental de blocos ao acaso, em parcelas subdivididas, com duas repetições. As características avaliadas foram: ciclo vegetativo, ciclo cultural, estatura de planta, diâmetro do colo, relação semente-casca, massa de mil sementes e produtividade de grãos. Os genótipos comportaram-se de maneira diferenciada, nas épocas de semeadura, para as características altura de inserção do primeiro racemo, ciclo vegetativo e ciclo cultural. O atraso na semeadura reduziu o rendimento de grãos de todos os genótipos avaliados. As maiores produtividades (1.500 kg ha-1) foram obtidas na semeadura feita no início do mês de novembro. São necessários mais estudos que incluam novos genótipos e maior amplitude da época de semeadura, envolvendo no mínimo o período compreendido entre os meses de outubro a dezembro para definir a melhor época de semeadura da mamona no Planalto Catarinense

Role of plakophilin-2 expression on exercise-related progression of arrhythmogenic right ventricular cardiomyopathy:a translational study

AIMS: Exercise increases arrhythmia risk and cardiomyopathy progression in arrhythmogenic right ventricular cardiomyopathy (ARVC) patients, but the mechanisms remain unknown. We investigated transcriptomic changes caused by endurance training in mice deficient in plakophilin-2 (PKP2cKO), a desmosomal protein important for intercalated disc formation, commonly mutated in ARVC and controls. METHODS AND RESULTS: Exercise alone caused transcriptional downregulation of genes coding intercalated disk proteins. The changes converged with those in sedentary and in exercised PKP2cKO mice. PKP2 loss caused cardiac contractile deficit, decreased muscle mass and increased functional/transcriptomic signatures of apoptosis, despite increased fractional shortening and calcium transient amplitude in single myocytes. Exercise accelerated cardiac dysfunction, an effect dampened by pre-training animals prior to PKP2-KO. Consistent with PKP2-dependent muscle mass deficit, cardiac dimensions in human athletes carrying PKP2 mutations were reduced, compared to matched controls. CONCLUSIONS: We speculate that exercise challenges a cardiomyocyte "desmosomal reserve" which, if impaired genetically (e.g., PKP2 loss), accelerates progression of cardiomyopathy

A Connexin40 Mutation Associated With a Malignant Variant of Progressive Familial Heart Block Type I

Background-Progressive familial heart block type I (PFHBI) is a hereditary arrhythmia characterized by progressive conduction disturbances in the His-Purkinje system. PFHBI has been linked to genes such as SCN5A that influence cardiac excitability but not to genes that influence cell-to-cell communication. Our goal was to explore whether nucleotide substitutions in genes coding for connexin proteins would associate with clinical cases of PFHBI and if so, to establish a genotype-cell phenotype correlation for that mutation. Methods and Results-We screened 156 probands with PFHBI. In addition to 12 sodium channel mutations, we found a germ line GJA5 (connexin40 [Cx40]) mutation (Q58L) in 1 family. Heterologous expression of Cx40-Q58L in connexin-deficient neuroblastoma cells resulted in marked reduction of junctional conductance (Cx40-wild type [WT], 22.2 ± 1.7 nS, n=14; Cx40-Q58L, 0.56 ± 0.34 nS, n=14; P <0.001) and diffuse localization of immunoreactive proteins in the vicinity of the plasma membrane without formation of gap junctions. Heteromeric cotransfection of Cx40-WT and Cx40-Q58L resulted in homogenous distribution of proteins in the plasma membrane rather than in membrane plaques in ̃ 50% of cells; well-defined gap junctions were observed in other cells. Junctional conductance values correlated with the distribution of gap junction plaques. Conclusions-Mutation Cx40-Q58L impairs gap junction formation at cell-cell interfaces. This is the first demonstration of a germ line mutation in a connexin gene that associates with inherited ventricular arrhythmias and emphasizes the importance of Cx40 in normal propagation in the specialized conduction system