Cooperation of translocase complexes in mitochondrial protein import

Most mitochondrial proteins are synthesized in the cytosol and imported into one of the four mitochondrial compartments: outer membrane, intermembrane space, inner membrane, and matrix. Each compartment contains protein complexes that interact with precursor proteins and promote their transport. These translocase complexes do not act as independent units but cooperate with each other and further membrane complexes in a dynamic manner. We propose that a regulated coupling of translocases is important for the coordination of preprotein translocation and efficient sorting to intramitochondrial compartments

Mdm38 interacts with ribosomes and is a component of the mitochondrial protein export machinery

Saccharomyces cerevisiae Mdm38 and Ylh47 are homologues of human Letm1, a protein implicated in Wolf-Hirschhorn syndrome. We analyzed the function of Mdm38 and Ylh47 in yeast mitochondria to gain insight into the role of Letm1. We find that mdm38Δ mitochondria have reduced amounts of certain mitochondrially encoded proteins and low levels of complex III and IV and accumulate unassembled Atp6 of complex V of the respiratory chain. Mdm38 is especially required for efficient transport of Atp6 and cytochrome b across the inner membrane, whereas Ylh47 plays a minor role in this process. Both Mdm38 and Ylh47 form stable complexes with mitochondrial ribosomes, similar to what has been reported for Oxa1, a central component of the mitochondrial export machinery. Our results indicate that Mdm38 functions as a component of an Oxa1-independent insertion machinery in the inner membrane and that Mdm38 plays a critical role in the biogenesis of the respiratory chain by coupling ribosome function to protein transport across the inner membrane

Symmetric and asymmetric action integration during cooperative object manipulation in virtual environments

Cooperation between multiple users in a virtual environment (VE) can take place at one of three levels. These are defined as where users can perceive each other (Level 1), individually change the scene (Level 2), or simultaneously act on and manipulate the same object (Level 3). Despite representing the highest level of cooperation, multi-user object manipulation has rarely been studied. This paper describes a behavioral experiment in which the piano movers' problem (maneuvering a large object through a restricted space) was used to investigate object manipulation by pairs of participants in a VE. Participants' interactions with the object were integrated together either symmetrically or asymmetrically. The former only allowed the common component of participants' actions to take place, but the latter used the mean. Symmetric action integration was superior for sections of the task when both participants had to perform similar actions, but if participants had to move in different ways (e.g., one maneuvering themselves through a narrow opening while the other traveled down a wide corridor) then asymmetric integration was superior. With both forms of integration, the extent to which participants coordinated their actions was poor and this led to a substantial cooperation overhead (the reduction in performance caused by having to cooperate with another person)

Mitochondrial precursor proteins are imported through a hydrophilic membrane environment

We have analyzed how translocation intermediates of imported mitochondrial precursor proteins, which span contact sites, interact with the mitochondrial membranes. F1-ATPase subunit β(F1β) was trapped at contact sites by importing it into Neurospora mitochondria in the presence of low levels of nucleoside triphosphates. This F1β translocation intermediate could be extracted from the membranes by treatment with protein denaturants such as alkaline pH or urea. By performing import at low temperatures, the ADP/ATP carrier was accumulated in contact sites of Neurospora mitochondria and cytochrome b2 in contact sites of yeast mitochondria. These translocation intermediates were also extractable from the membranes at alkaline pH. Thus, translocation of precursor proteins across mitochondrial membranes seems to occur through an environment which is accessible to aqueous perturbants. We propose that proteinaceous structures are essential components of a translocation apparatus present in contact sites

A J-protein is an essential subunit of the presequence translocase–associated protein import motor of mitochondria

Transport of preproteins into the mitochondrial matrix is mediated by the presequence translocase–associated motor (PAM). Three essential subunits of the motor are known: mitochondrial Hsp70 (mtHsp70); the peripheral membrane protein Tim44; and the nucleotide exchange factor Mge1. We have identified the fourth essential subunit of the PAM, an essential inner membrane protein of 18 kD with a J-domain that stimulates the ATPase activity of mtHsp70. The novel J-protein (encoded by PAM18/YLR008c/TIM14) is required for the interaction of mtHsp70 with Tim44 and protein translocation into the matrix. We conclude that the reaction cycle of the PAM of mitochondria involves an essential J-protein

El correo electrónico en la consulta de Parkinson: ¿soluciones a un clic? // Use of e-mail for Parkinson's disease consultations: Are answers just a clic away?

INTRODUCCION: La problemática de los trastornos del movimiento (TM) es compleja y la duración y frecuencia de las consultas presenciales puede estar limitada por problemas de espacio y tiempo. Analizamos el funcionamiento de un servicio de atención por correo electrónico institucional para médicos de Atención Primaria (MAP) y pacientes en la Unidad de Trastornos del Movimiento (UTM). METODOS: Se revisaron retrospectivamente los correos electrónicos enviados y recibidos en un periodo de 4 meses, un año tras su implantación. La dirección se proporcionaba en consulta y mediante sesiones informativas a los MAP del área. Se analizaron datos clínicos y demográficos de los pacientes, tipo de interlocutor, número de consultas, motivo y actuaciones derivadas de ellas. RESULTADOS: Del 1 de enero al 30 de abril de 2015 se recibieron 137 correos de 63 pacientes (43% varones; edad 71 ± 10,5 años) diagnosticados de enfermedad de Parkinson (76%), parkinsonismos atípicos (10%) y otros (14%), y se enviaron 116 respuestas. En 20 casos (32%) fueron redactados por el paciente, en 38 (60%) por sus familiares y en 5 (8%) por MAP. Los motivos de consulta fueron clínicos en 50 casos (80%): deterioro clínico (16; 32%), nuevos síntomas (14; 28%), efectos secundarios o dudas sobre medicación (20; 40%). Como consecuencia, se adelantó una cita programada en 9 casos (14%), mientras que el resto se solucionaron por correo electrónico. En 13 (20%), el motivo de consulta fue burocrático: relacionado con citas (11, 85%) y solicitud de informe (2, 15%). La satisfacción fue generalizada, sin constituir una sobrecarga asistencial excesiva para los facultativos responsables. CONCLUSIONES: La implantación de una consulta por correo electrónico es factible en UTM, facilita la comunicación médico-paciente y la continuidad asistencial con Atención Primaria. // INTRODUCTION: The clinical problems of patients with movement disorders (MD) are complex, and the duration and frequency of face-to-face consultations may be insufficient to meet their needs. We analysed the implementation of an e-mail-based query service for our MD unit's patients and their primary care physicians (PCPs). METHODS: We retrospectively reviewed all consecutive emails sent and received over a period of 4 months, one year after implementation of the e-mail inquiry system. All patients received the during consultations, and PCPs, during scheduled informative meetings. We recorded and later analysed the profile of the questioner, patients’ demographic and clinical data, number of queries, reason for consultation, and actions taken. RESULTS: From 1 January 2015 to 30 April 2015, the service received 137 emails from 63 patients (43% male, mean age 71 ± 10.5) diagnosed with Parkinson's disease (76%), atypical parkinsonism (10%), and others (14%); 116 responses were sent. Twenty (32%) emails were written by patients, 38 (60%) by their caregivers, and 5 (8%) by their PCPs. The reasons for consultation were clinical in 50 cases (80%): 16 (32%) described clinical deterioration, 14 (28%) onset of new symptoms, and 20 (40%) side effects or concerns about medications. In 13 cases (20%), the query was bureaucratic: 11 were related to appointments (85%) and 2 were requests for clinical reports (15%). In response, new appointments were scheduled in 9 cases (14%), while the rest of the questions were answered by email. Patients were satisfied overall and the additional care burden on specialists was not excessive. CONCLUSIONS: Implementing an e-mail-based consultation system is feasible in MD units. It facilitates both communication between neurologists and patients and continued care in the primary care setting

Neurochemical Changes in the Mouse Hippocampus Underlying the Antidepressant Effect of Genetic Deletion of P2X7 Receptors.

Recent investigations have revealed that the genetic deletion of P2X7 receptors (P2rx7) results in an antidepressant phenotype in mice. However, the link between the deficiency of P2rx7 and changes in behavior has not yet been explored. In the present study, we studied the effect of genetic deletion of P2rx7 on neurochemical changes in the hippocampus that might underlie the antidepressant phenotype. P2X7 receptor deficient mice (P2rx7-/-) displayed decreased immobility in the tail suspension test (TST) and an attenuated anhedonia response in the sucrose preference test (SPT) following bacterial endotoxin (LPS) challenge. The attenuated anhedonia was reproduced through systemic treatments with P2rx7 antagonists. The activation of P2rx7 resulted in the concentration-dependent release of [3H]glutamate in P2rx7+/+ but not P2rx7-/- mice, and the NR2B subunit mRNA and protein was upregulated in the hippocampus of P2rx7-/- mice. The brain-derived neurotrophic factor (BDNF) expression was higher in saline but not LPS-treated P2rx7-/- mice; the P2rx7 antagonist Brilliant blue G elevated and the P2rx7 agonist benzoylbenzoyl ATP (BzATP) reduced BDNF level. This effect was dependent on the activation of NMDA and non-NMDA receptors but not on Group I metabotropic glutamate receptors (mGluR1,5). An increased 5-bromo-2-deoxyuridine (BrdU) incorporation was also observed in the dentate gyrus derived from P2rx7-/- mice. Basal level of 5-HT was increased, whereas the 5HIAA/5-HT ratio was lower in the hippocampus of P2rx7-/- mice, which accompanied the increased uptake of [3H]5-HT and an elevated number of [3H]citalopram binding sites. The LPS-induced elevation of 5-HT level was absent in P2rx7-/- mice. In conclusion there are several potential mechanisms for the antidepressant phenotype of P2rx7-/- mice, such as the absence of P2rx7-mediated glutamate release, elevated basal BDNF production, enhanced neurogenesis and increased 5-HT bioavailability in the hippocampus