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Faccenda D.,Royal Veterinary College University of London | Tan C.H.,University College London | Seraphim A.,University College London | Duchen M.R.,University College London | And 3 more authors.
Cell Death and Differentiation

Mitochondrial structure has a central role both in energy conversion and in the regulation of cell death. We have previously shown that IF 1 protects cells from necrotic cell death and supports cristae structure by promoting the oligomerisation of the F 1 F o-ATPsynthase. As IF 1 is upregulated in a large proportion of human cancers, we have here explored its contribution to the progression of apoptosis and report that an increased expression of IF 1, relative to the F 1 F o-ATPsynthase, protects cells from apoptotic death. We show that IF 1 expression serves as a checkpoint for the release of Cytochrome c (Cyt c) and hence the completion of the apoptotic program. We show that the progression of apoptosis engages an amplification pathway mediated by: (i) Cyt c-dependent release of ER Ca 2+, (ii) Ca 2+-dependent recruitment of the GTPase Dynamin-related protein 1 (Drp1), (iii) Bax insertion into the outer mitochondrial membrane and (iv) further release of Cyt c. This pathway is accelerated by suppression of IF 1 and delayed by its overexpression. IF 1 overexpression is associated with the preservation of mitochondrial morphology and ultrastructure, consistent with a central role for IF 1 as a determinant of the inner membrane architecture and with the role of mitochondrial ultrastructure in the regulation of Cyt c release. These data suggest that IF 1 is an antiapoptotic and potentially tumorigenic factor and may be a valuable predictor of responsiveness to chemotherapy. © 2013 Macmillan Publishers Limited All rights reserved. Source

East D.A.,Royal Veterinary College University of London | Campanella M.,Royal Veterinary College University of London | Campanella M.,University College London | Campanella M.,European Brain Research Institute EBRI

Calcium (Ca2+) has long been known as a ubiquitous intracellular second messenger, exploited by cells to control processes as diverse as development, proliferation, learning, muscle contraction and secretion. The spatial and temporal patterns of these Ca2+-associated signals, as well as their amplitude, is precisely controlled to create gradients of the ion, varying considerably depending on cell type and function. Tuning of intracellular Ca2+ is achieved in part by the buffering role of mitochondria, whose unperturbed function is essential for maintaining cellular energy balance. Quality of mitochondria is ensured by the process of targeted autophagy or mitophagy, which depends on a molecular cascade driving the catabolic process of autophagy toward damaged or deficient organelles for elimination via the lysosomal pathway. Nonspecific and targeted autophagy are highly regulated processes fundamental to cell growth and tissue homeostasis, allowing resources to be reallocated in nutrient-deprived cells as well as being instrumental in the repair of damaged organelles or the elimination of those in excess. Given the role of Ca2+ signaling in many fundamental cellular processes requiring precise regulation, the involvement of Ca 2+ in autophagy is still somewhat ill-defined, and only in the past few years has evidence emerged linking the two. This minireview aims to summarize recent work implicating Ca2+ as an important regulator of autophagy, outlining a role for Ca2+ that may be even more critical in the regulation of targeted mitochondrial autophagy. © 2013 Landes Bioscience. Source

Bobba A.,CNR Institute of Neuroscience | Amadoro G.,CNR Institute of Neuroscience | Petragallo V.A.,CNR Institute of Neuroscience | Calissano P.,European Brain Research Institute EBRI | Atlante A.,CNR Institute of Neuroscience
Biochimica et Biophysica Acta - Bioenergetics

To find out whether and how the adenine nucleotide translocator-1 (ANT-1) inhibition due to NH2htau and Aβ1-42 is due to an interplay between these two Alzheimer's peptides, ROS and ANT-1 thiols, use was made of mersalyl, a reversible alkylating agent of thiol groups that are oriented toward the external hydrophilic phase, to selectively block and protect, in a reversible manner, the -SH groups of ANT-1. The rate of ATP appearance outside mitochondria was measured as the increase in NADPH absorbance which occurs, following external addition of ADP, when ATP is produced by oxidative phosphorylation and exported from mitochondria in the presence of glucose, hexokinase and glucose-6-phosphate dehydrogenase. We found that the mitochondrial superoxide anions, whose production is induced at the level of Complex I by externally added Aβ1-42 and whose release from mitochondria is significantly reduced by the addition of the VDAC inhibitor DIDS, modify the thiol group/s present at the active site of mitochondrial ANT-1, impair ANT-1 in a mersalyl-prevented manner and abrogate the toxic effect of NH2htau on ANT-1 when Aβ1-42 is already present. A molecular mechanism is proposed in which the pathological Aβ-NH2htau interplay on ANT-1 in Alzheimer's neurons involves the thiol redox state of ANT-1 and the Aβ1-42-induced ROS increase. This result represents an important innovation because it suggests the possibility of using various strategies to protect cells at the mitochondrial level, by stabilizing or restoring mitochondrial function or by interfering with the energy metabolism providing a promising tool for treating or preventing AD. © 2013 Elsevier B.V. Source

Bobba A.,CNR Institute of Biomembrane and Bioenergetics | Amadoro G.,CNR Institute of Neuroscience | Valenti D.,CNR Institute of Biomembrane and Bioenergetics | Corsetti V.,European Brain Research Institute EBRI | And 2 more authors.

Here we investigate the effect of β-amyloid on mitochondrial respiratory function, i.e.mitochondrial oxygen consumption and membrane potential generation as well as the individual activities of both the mitochondrial Complexes I-IV, that compose mitochondrial electron transport chain, and the ATP synthase, by using homogenate from cerebellar granule cells, treated with low concentrations of β-amyloid, and Alzheimer synaptic-enriched brain samples. We found that β-amyloid caused both a selective defect in Complex I activity associated with an increase (5 fold) of intracellular reactive oxygen species and an impairment of Complex IV likely due to membrane lipid peroxidation. In addition, a 130% increase of the GSSG/GSH ratio was measured in Alzheimer brains with respect to age-matched controls. Knowing the mechanisms of action of β-amyloid could allow to mitigate or even to interrupt the toxic cascade that leads a cell to death. The results of this study represent an important innovation because they offer the possibility to act at mitochondrial level and on specific sites to protect cells, for example by preventing the interaction of β-amyloid with the identified targets, by stabilizing or by restoring mitochondrial function or by interfering with the energy metabolism. © 2013 Elsevier B.V. and Mitochondria Research Society. Source

Mendez P.,European Brain Research Institute EBRI
Neural plasticity

Cortical structures of the adult mammalian brain are characterized by a spectacular diversity of inhibitory interneurons, which use GABA as neurotransmitter. GABAergic neurotransmission is fundamental for integrating and filtering incoming information and dictating postsynaptic neuronal spike timing, therefore providing a tight temporal code used by each neuron, or ensemble of neurons, to perform sophisticated computational operations. However, the heterogeneity of cortical GABAergic cells is associated to equally diverse properties governing intrinsic excitability as well as strength, dynamic range, spatial extent, anatomical localization, and molecular components of inhibitory synaptic connections that they form with pyramidal neurons. Recent studies showed that similarly to their excitatory (glutamatergic) counterparts, also inhibitory synapses can undergo activity-dependent changes in their strength. Here, some aspects related to plasticity and modulation of adult cortical and hippocampal GABAergic synaptic transmission will be reviewed, aiming at providing a fresh perspective towards the elucidation of the role played by specific cellular elements of cortical microcircuits during both physiological and pathological operations. Source

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