Mitochondrial Alterations in PINK1 Deficient Cells Are Influenced by Calcineurin-Dependent Dephosphorylation of Dynamin-Related Protein 1

PTEN-induced novel kinase 1 (PINK1) mutations are associated with autosomal recessive parkinsonism. Previous studies have shown that PINK1 influences both mitochondrial function and morphology although it is not clearly established which of these are primary events and which are secondary. Here, we describe a novel mechanism linking mitochondrial dysfunction and alterations in mitochondrial morphology related to PINK1. Cell lines were generated by stably transducing human dopaminergic M17 cells with lentiviral constructs that increased or knocked down PINK1. As in previous studies, PINK1 deficient cells have lower mitochondrial membrane potential and are more sensitive to the toxic effects of mitochondrial complex I inhibitors. We also show that wild-type PINK1, but not recessive mutant or kinase dead versions, protects against rotenone-induced mitochondrial fragmentation whereas PINK1 deficient cells show lower mitochondrial connectivity. Expression of dynamin-related protein 1 (Drp1) exaggerates PINK1 deficiency phenotypes and Drp1 RNAi rescues them. We also show that Drp1 is dephosphorylated in PINK1 deficient cells due to activation of the calcium-dependent phosphatase calcineurin. Accordingly, the calcineurin inhibitor FK506 blocks both Drp1 dephosphorylation and loss of mitochondrial integrity in PINK1 deficient cells but does not fully rescue mitochondrial membrane potential. We propose that alterations in mitochondrial connectivity in this system are secondary to functional effects on mitochondrial membrane potential

Gene Expression Changes in the Prefrontal Cortex, Anterior Cingulate Cortex and Nucleus Accumbens of Mood Disorders Subjects That Committed Suicide

Suicidal behaviors are frequent in mood disorders patients but only a subset of them ever complete suicide. Understanding predisposing factors for suicidal behaviors in high risk populations is of major importance for the prevention and treatment of suicidal behaviors. The objective of this project was to investigate gene expression changes associated with suicide in brains of mood disorder patients by microarrays (Affymetrix HG-U133 Plus2.0) in the dorsolateral prefrontal cortex (DLPFC: 6 Non-suicides, 15 suicides), the anterior cingulate cortex (ACC: 6NS, 9S) and the nucleus accumbens (NAcc: 8NS, 13S). ANCOVA was used to control for age, gender, pH and RNA degradation, with P≤0.01 and fold change±1.25 as criteria for significance. Pathway analysis revealed serotonergic signaling alterations in the DLPFC and glucocorticoid signaling alterations in the ACC and NAcc. The gene with the lowest p-value in the DLPFC was the 5-HT2A gene, previously associated both with suicide and mood disorders. In the ACC 6 metallothionein genes were down-regulated in suicide (MT1E, MT1F, MT1G, MT1H, MT1X, MT2A) and three were down-regulated in the NAcc (MT1F, MT1G, MT1H). Differential expression of selected genes was confirmed by qPCR, we confirmed the 5-HT2A alterations and the global down-regulation of members of the metallothionein subfamilies MT 1 and 2 in suicide completers. MTs 1 and 2 are neuro-protective following stress and glucocorticoid stimulations, suggesting that in suicide victims neuroprotective response to stress and cortisol may be diminished. Our results thus suggest that suicide-specific expression changes in mood disorders involve both glucocorticoids regulated metallothioneins and serotonergic signaling in different regions of the brain

Search for eccentric black hole coalescences during the third observing run of LIGO and Virgo

Despite the growing number of confident binary black hole coalescences observed through gravitational waves so far, the astrophysical origin of these binaries remains uncertain. Orbital eccentricity is one of the clearest tracers of binary formation channels. Identifying binary eccentricity, however, remains challenging due to the limited availability of gravitational waveforms that include effects of eccentricity. Here, we present observational results for a waveform-independent search sensitive to eccentric black hole coalescences, covering the third observing run (O3) of the LIGO and Virgo detectors. We identified no new high-significance candidates beyond those that were already identified with searches focusing on quasi-circular binaries. We determine the sensitivity of our search to high-mass (total mass M>70 M⊙) binaries covering eccentricities up to 0.3 at 15 Hz orbital frequency, and use this to compare model predictions to search results. Assuming all detections are indeed quasi-circular, for our fiducial population model, we place an upper limit for the merger rate density of high-mass binaries with eccentricities 0<e≤0.3 at 0.33 Gpc−3 yr−1 at 90\% confidence level

Heterogeneity of NMDA receptors labelled with [³H]3-((±)-2-carboxypiperazin-4-yl)propyl-1-phosphonic acid ([³H]CPP): receptor status in Alzheimer's disease brains

The binding of [3H]3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid ([3H]CPP) was studied in rat and human brain synaptic membranes. Specific binding was saturable, reversible and inhibited by a range of compounds active at N-methyl-D-aspartate (NMDA) receptors such as 2-amino-5-phosphonopentanoate (AP5), 2-amino-7-phosphonoheptanoate (AP7), NMDA and cis-2,4-methanoglutamate. Binding was heterogeneous as evidenced by non-linear Scatchard plots and Hill coefficients for binding inhibitors significantly different from unity. LIGAND analysis of the binding data indicated the likely presence of two distinct binding components for CPP, one of high (Kd values approx. = 70 nM) and the other of low (Kd values approx. 5 μM) affinity. Possible alterations in the binding of [3H]CPP to either site were investigated in medial frontal and medial temporal cortex from Alzheimer's disease brains and compared with control tissues, carefully matched for age and postmortem delay. While there were considerable inter-individual variations in binding, no significant differences were detected either between brain regions in either Alzheimer or control subjects, or between Alzheimer's disease and control brains. These data suggest the presence of at least two components of [3H]CPP binding in both rat and human brain tissue. The integrity of neither of these components is altered in Alzheimer's disease, consistent with a lack of gross alterations of NMDA receptors in this disorder.</p

Characterisation, Density, and Distribution of Kainate Receptors in Normal and Alzheimer's Diseased Human Brain

Abstract: The specific binding of [3H]kainic acid was investigated in membrane preparations from human parietal cortex obtained postmortem. Saturation studies revealed that binding occurred to a single population of sites with a KD of 15 nM and a Bmax of 110 fmol/mg of protein. The kinetically determined dissociation constant for these sites agreed well with that obtained from saturation analyses. Pharmacological characterisation of these sites gave a profile consistent with those reported for kainate receptor sites in animal brain. The integrity of kainate receptors was studied in several brain regions from six patients who had died of Alzheimer's disease and from six closely matched control subjects. No change in either the affinity or the number of kainate receptors was seen in any of the regions studied, despite the loss of neo‐cortical and hippocampal glutamatergic terminals in the Alzheimer's diseased brains, as previously reported.</p

PTEN, a negative regulator of PI3 kinase signalling, alters tau phosphorylation in cells by mechanisms independent of GSK-3

Deregulation of PTEN/Akt signalling has been recently implicated in the pathogenesis of Alzheimer's disease (AD), but the effects on the molecular processes underlying AD pathology have not yet been fully described. Here we report that overexpression of PTEN reduces tau phosphorylation in CHO cells. This effect was abrogated by mutant PTEN constructs with either a catalytically inactive point mutation (C124S) or with only inactive lipid phosphatase activity (G129E), suggesting an indirect, lipid phosphatase-dependent process. The predominant effects of PTEN on tau appeared to be mediated by reducing ERK1/2 activity, but were independent of Akt, GSK-3, JNK and the tau phosphatases PP1 and PP2A. Our studies provide evidence for an effect of PTEN on the phosphorylation of tau in AD pathogenesis, and provide some insight into the mechanisms through which deregulation of PTEN may contribute towards the progression of tauopathy