Molecular determinants of pH regulation in the cardiac Na+-Ca2+ exchanger.

The cardiac Na+-Ca2+ exchanger (NCX) plays a critical role in the heart by extruding Ca2+ after each contraction and thus regulates cardiac contractility. The activity of NCX is strongly inhibited by cytosolic protons, which suggests that intracellular acidification will have important effects on heart contractility. However, the mechanisms underlying this inhibition remain elusive. It has been suggested that pH regulation originates from the competitive binding of protons to two Ca2+-binding domains within the large cytoplasmic loop of NCX and requires inactivation by intracellular Na+ to fully develop. By combining mutagenesis and electrophysiology, we demonstrate that NCX pH modulation is an allosteric mechanism distinct from Na+ and Ca2+ regulation, and we show that cytoplasmic Na+ can affect the sensitivity of NCX to protons. We further identify two histidines (His 124 and His 165) that are important for NCX proton sensitivity and show that His 165 plays the dominant role. Our results reveal a complex interplay between the different allosteric mechanisms that regulate the activity of NCX. Because of the central role of NCX in cardiac function, these findings are important for our understanding of heart pathophysiology

The RCK2 domain of the human BKCa channel is a calcium sensor

Large conductance voltage and Ca2+-dependent K+ channels (BKCa) are activated by both membrane depolarization and intracellular Ca2+. Recent studies on bacterial channels have proposed that a Ca2+-induced conformational change within specialized regulators of K+ conductance (RCK) domains is responsible for channel gating. Each pore-forming α subunit of the homotetrameric BKCa channel is expected to contain two intracellular RCK domains. The first RCK domain in BKCa channels (RCK1) has been shown to contain residues critical for Ca2+ sensitivity, possibly participating in the formation of a Ca2+-binding site. The location and structure of the second RCK domain in the BKCa channel (RCK2) is still being examined, and the presence of a high-affinity Ca2+-binding site within this region is not yet established. Here, we present a structure-based alignment of the C terminus of BKCa and prokaryotic RCK domains that reveal the location of a second RCK domain in human BKCa channels (hSloRCK2). hSloRCK2 includes a high-affinity Ca2+-binding site (Ca bowl) and contains similar secondary structural elements as the bacterial RCK domains. Using CD spectroscopy, we provide evidence that hSloRCK2 undergoes a Ca2+-induced change in conformation, associated with an α-to-β structural transition. We also show that the Ca bowl is an essential element for the Ca2+-induced rearrangement of hSloRCK2. We speculate that the molecular rearrangements of RCK2 likely underlie the Ca2+-dependent gating mechanism of BKCa channels. A structural model of the heterodimeric complex of hSloRCK1 and hSloRCK2 domains is discussed

Dilution of seawater affects the Ca2 + transport in the outer mantle epithelium of crassostrea gigas

Varying salinities of coastal waters are likely to affect the physiology and ion transport capabilities of calcifying marine organisms such as bivalves. To investigate the physiological effect of decreased environmental salinity in bivalves, adult oysters (Crassostrea gigas) were exposed for 14 days to 50% seawater (14) and the effects on mantle ion transport, electrophysiology and the expression of Ca2+ transporters and channels relative to animals maintained in full strength sea water (28) was evaluated. Exposure of oysters to a salinity of 14 decreased the active mantle transepithelial ion transport and specifically affected Ca2+ transfer. Gene expression of the Na+/K+-ATPase and the sarco(endo)plasmic reticulum Ca2+-ATPase was decreased whereas the expression of the T-type voltage-gated Ca channel and the Na+/Ca2+-exchanger increased compared to animals maintained in full SW. The results indicate that decreased environmental salinities will most likely affect not only osmoregulation but also bivalve biomineralization and shell formation.Funding Agency European Union (EU) 605051 Swedish Mariculture Research Center, SWEMARC, University of Gothenburg Herbert & Karin Jacobssons Stiftelse 15/h17 Helge Ax:son Johnsons Stiftelse F18-0128 Portuguese Foundation for Science and Technology UID/Multi/04326/2019 Portuguese Foundation for Science and Technology UID/Multi/04326/2019 FCT, under the "Norma Transitoria" DL57/2016/CP1361/CT0020 DL57/2016/CP1361/CT0011info:eu-repo/semantics/publishedVersio

An Amphipathic α-Helix Directs Palmitoylation of the Large Intracellular Loop of the Sodium/Calcium Exchanger

The electrogenic sodium/calcium exchanger (NCX) mediates bidirectional calcium transport controlled by the transmembrane sodium gradient. NCX inactivation occurs in the absence of phosphatidylinositol 4,5-bisphosphate and is facilitated by palmitoylation of a single cysteine at position 739 within the large intracellular loop of NCX. The aim of this investigation was to identify the structural determinants of NCX1 palmitoylation. Full-length NCX1 (FL-NCX1) and a YFP fusion protein of the NCX1 large intracellular loop (YFP-NCX1) were expressed in HEK cells. Single amino acid changes around Cys-739 in FL-NCX1 and deletions on the N-terminal side of Cys-739 in YFP-NCX1 did not affect NCX1 palmitoylation, with the exception of the rare human polymorphism S738F, which enhanced FL-NCX1 palmitoylation, and D741A, which modestly reduced it. In contrast, deletion of a 21-amino acid segment enriched in aromatic amino acids on the C-terminal side of Cys-739 abolished YFP-NCX1 palmitoylation. We hypothesized that this segment forms an amphipathic α-helix whose properties facilitate Cys-739 palmitoylation. Introduction of negatively charged amino acids to the hydrophobic face or of helix-breaking prolines impaired palmitoylation of both YFP-NCX1 and FL-NCX1. Alanine mutations on the hydrophilic face of the helix significantly reduced FL-NCX1 palmitoylation. Of note, when the helix-containing segment was introduced adjacent to cysteines that are not normally palmitoylated, they became palmitoylation sites. In conclusion, we have identified an amphipathic α-helix in the NCX1 large intracellular loop that controls NCX1 palmitoylation. NCX1 palmitoylation is governed by a distal secondary structure element rather than by local primary sequence

A satisfação profissional na gestão participativa

O presente trabalho visa descrever os conceitos de Gestão Participativa aliada à satisfação do profissional e suas inflexões. O objetivo é compreender como a gestão participativa de uma empresa beneficia ou não as pessoas, do ponto de vista da não alienação, e como a mesma influencia comportamentos e atitudes dos funcionários que nela trabalham. Além disto, dirige o tema sobre a ótica da Psicologia demonstrando como a mesma pode contribuir no entendimento deste modelo de gestão e, consequentemente, como este influencia na realização profissional de cada indivíduo. Atualmente as empresas estão remodelando seus princípios e valores a fim de atender e investir em seus colaboradores e em suas necessidades individuais as quais estão intimamente ligadas ao desenvolvimento profissional. A metodologia adotada será de um estudo teórico seguido de exemplos empíricos e ilustrativosThis paper aims to describe the concepts of Participatory Management in addition to professional satisfaction and their inflections. The objective is to comprehend how a participatory management of a company benefits or not people, in terms of alienation, and how it influences behavior and attitudes of employees who work there. Moreover, the theme runs on the perspective of psychology, making a demonstration on how it can contribute to the comprehension of this management model and how it affects the professional achievement of each worker. Now the companies are reshaping their principles in order to attend and invest in their employees and their individual needs which are closely tied to professional development. The methodology will be followed by a theoretical study and empirical examples and illustratin

Estudo sobre as percepções na relação médico veterinário, tutor e estudante de medicina veterinária em relação à clínica veterinária de pequenos animais no hospital de clínicas veterinárias da UFRGS

Apesar de não existir exigências e padrões sobre o processo de comunicação na medicina veterinária, este conceito está mudando. Estudos indicam que para o médico veterinário obter sucesso econômico, por exemplo, pontos críticos como habilidade, conhecimento, aptidões e atitudes do profissional, incluindo a comunicação, devem ser considerados. A medicina veterinária tem sofrido mudanças significativas devido à incorporação dos animais como membros da família, aumentando as responsabilidades dos veterinários em atender e entender as expectativas dos clientes. O presente estudo foi realizado com o objetivo de compreender as percepções de estudantes de medicina veterinária, tutores de animais e veterinários sobre a relação médico veterinário – proprietário. Foi distribuído para cada categoria um questionário específico que buscava compreender a realidade sócio-econômica do entrevistado e as suas percepções sobre a relação tutor-veterinário. Com base nos resultados, apontaram não haver divergências significativas de exigência das características apontadas pelas três categorias (veterinários, estudantes e proprietários) para um bom atendimento do proprietário e seu animal pelo veterinário. Como características importantes para um atendimento de qualidade do veterinário, foram destacadas pelas três categorias o “conhecimento técnico”, “ser atencioso com o proprietário e seu animal”, “expor alternativas de terapêutica” e “habilidade com o animal”. Observou-se também que há a necessidade do aprimoramento do conhecimento das habilidades de comunicação durante a graduação, evidenciado tanto pelos estudantes, como pelos veterinários e que os mesmos concordam com a afirmação de que a universidade deveria incentivar este tipo de conhecimento. Este trabalho é um estudo piloto e mais estudos devem ser realizados para uma melhor compreensão da relação médico veterinário e proprietários de animais.Although there are neither requirements nor standards for the communication process in veterinary medicine, this concept is changing. Studies indicate that, in order to obtain economic success, critical issues such as the veterinarian’s skills, knowledge, capabilities and attitudes, including the communication skills, should be considered. Veterinary medicine has been going through significant changes due to the incorporation of animals as family members, increasing the responsibilities of veterinarians to meet and understand customers’ expectations. This study was conducted with the aim of understanding the perceptions of the relationship among the veterinary doctor and pet owners, in the case of veterinary students, animal tutors and veterinarians. A specific questionnaire was distributed for each category that sought to understand the socio-economic realities of the interviewed and their perceptions of the tutor-veterinarian relationship. Based on the results, showed no significant differences in requirement of the characteristics indicated by the three categories (veterinarians, students and owners) for a good veterinarian service. How important characteristics for a veterinarian's quality of care, were highlighted by the three categories the "technical knowledge", "be considerate of the owner and his animal", "expose therapeutic alternatives" and "skill with the animal." It is also noted that there is a need for improving the communication skills during graduation, what is evidenced both by students and by veterinarians. Both groups agree with the statement that the university should encourage this type of knowledge. This work is a pilot study and further studies should be conducted to better understand the relationship among veterinarian and pet owners

Dual network structure of the AV node

Biological systems, particularly the brain, are frequently analyzed as networks, conveying mechanistic insights into their function and pathophysiology. This is the first study of a functional network of cardiac tissue. We use calcium imaging to obtain two functional networks in a subsidiary but essential pacemaker of the heart, the atrioventricular node (AVN). The AVN is a small cellular structure with dual functions: a) to delay the pacemaker signal passing from the sinoatrial node (SAN) to the ventricles, and b) to serve as a back-up pacemaker should the primary SAN pacemaker fail. Failure of the AVN can lead to syncope and death. We found that the shortest path lengths and clustering coefficients of the AVN are remarkably similar to those of the brain. The network is ``small-world," thus optimized for energy use vs transmission efficiency. We further study the network properties of AVN tissue with knock-out of the sodium-calcium exchange transporter. In this case, the average shortest path-lengths remained nearly unchanged showing network resilience, while the clustering coefficient was somewhat reduced, similar to schizophrenia in brain networks. When we removed the global action potential using principal component analysis (PCA) in wild-type model, the network lost its ``small-world" characteristics with less information-passing efficiency due to longer shortest path lengths but more robust signal propagation resulting from higher clustering. These two wild-type networks (with and without global action potential) may correspond to fast and slow conduction pathways. Laslty, a one-parameter non-linear preferential attachment model is a good fit to all three AVN networks.Comment: 14 pages, 8 figures at the end of the manuscript, two videos and three datasets in the Source folde