The complex molecule of the title compound, [Rh2{N(C6H5)COCH3}4(C8H7N)2], exhibits inversion symmetry. The four acetamidate ligands bridging the dirhodium core are arranged in a 2,2-trans manner with two N atoms and two O atoms coordinating to each RhIIatom trans to one another. The Neq - Rh - Rh - Oeq torsion angles on the acetamidate bridge vary between -4.07 (5) and -6.78 (7)°. The axial nitrile ligands complete the distorted octahedral coordination sphere of each RhIIatom and show a nonlinear coordination with Rh - N - C bond angles of 151.6 (3) and 152.5 (3)°. The bond lengths of the two nitrile triple bonds are 1.133 (5) and 1.137 (5) Å.

Résumé : La schizophrénie est une maladie mentale chronique caractérisée par trois types différents de symptômes cliniques : positifs (hallucinations), négatifs (manque de motivation) et cognitifs (dysfonction exécutive). Parmi de nombreuses perturbations neurochimiques, un débalancement entre la production des espèces réactives de l’oxygène et l’activité des enzymes antioxydantes, suggère l’existence de dysfonctions mitochondriales. Notre laboratoire a récemment développé un modèle juvénile à double atteinte de schizophrénie, chez la souris, combinant deux facteurs de risques environnementaux (inflammation immunitaire gestationnelle par l’injection de polyIC, suivie à l’âge juvénile d’un stress de contention du jour postnatal 33 à 35) afin de mieux comprendre la phase précoce de la maladie. Nous avons présenté précédemment, des anomalies comportementales et neurochimiques, incluant un stress oxydatif (mesuré par une augmentation de la carbonylation des protéines), nous permettant de valider le modèle. De plus, un antioxydant, l’acide lipoïque (AL) renverse ces déficits, appuyant les anomalies observées. Ici, nous avons évalué la fonction mitochondriale dans ce modèle juvénile à double atteinte de schizophrénie chez la souris. L’activité mitochondriale a été déterminée dans deux régions d’intérêt (cortex préfrontal (PFC) et striatum) associées à la schizophrénie. Nos mesures ont été faites en stade 3, avec des substrats pour le complexe I (glutamate-malate + ADP) et complexe II (succinate + ADP) induisant la respiration mitochondriale. Nous avons observé une augmentation de l’activité respiratoire induite par le complexe I dans le PFC et le striatum dans les deux sexes mais une augmentation de l’activité induite par le complexe II seulement chez les mâles. Le traitement à l’AL prévient seulement l’augmentation de la respiration induite par le complexe II chez les mâles mais n’a pas d’effet sur l’activité induite par le complexe I. Les niveaux d’expression protéique des différents complexes de la chaine respiratoire, des groupements carbonyl ainsi que des protéines de fission/fusion ne sont pas modifiés. En conclusion, notre modèle juvénile à double atteinte de schizophrénie montre une augmentation de l’activité respiratoire induite par le complexe II chez les mâles, sans changement de l’expression protéique. D’autres expériences sont requises pour comprendre l’origine de ces modifications. / Abstract : Schizophrenia is a chronic mental illness characterized by different clinical symptoms with three core features: positive (eg hallucinations), negative (eg lack of motivation) and cognitive (eg executive dysfunction). Among a large array of neurochemical disturbances, imbalance between production of reactive oxygen species and activity of antioxidant enzymes, convincingly points toward mitochondrial dysfunction. Our laboratory has recently developed a juvenile murine two-hit model (THM) of schizophrenia based on the combination of two environmental risk factors (gestational inflammation induced by poly IC, followed by juvenile restraint stress at postnatal days 33-35) to gain a better understanding of the early disease onset. We previously reported relevant behavioral and neurochemical disturbances, including oxidative stress (as assessed by an increase in protein carbonylation), thus providing preliminary validation of this THM of schizophrenia. Moreover, the antioxidant lipoic acid (LA) reversed these deficits, thereby pointing to a key role of oxidative stress. Here, we investigated mitochondrial function in this juvenile murine THM of schizophrenia. The mitochondrial activity was determined using the Mitoxpress commercial kit within two relevant regions (prefrontal cortex (PFC) and striatum) associated with schizophrenia. Our measures were performed in state 3, with substrates for complex I (glutamatemalate + ADP) and complex II (succinate + ADP) inducing mitochondrial respiratory activity. We observed an increase in complex I induced respiratory activity in the PFC and striatum in both sexes but an increase in complex II activity only in males. LA treatment prevented this increase only in complex II induced respiration in males but had no effect on complex I induced activity. Expression levels of the different respiratory chain complexes were not modified under our conditions, as well as fission/fusion protein and carbonyl group levels. In conclusion, our juvenile two-hit model of schizophrenia shows an increase in mitochondrial activity reversed by lipoic acid treatment, specifically in complex II induced respiratory activity in males, without any change in respiratory chain protein expression. Further investigations are required to determine the causes and consequences of these modifications.

Increased secretion of very low-density lipoprotein (VLDL), a triglyceride-rich lipoprotein, by the liver causes hypertriglyceridemia, which is a major risk factor for the development of atherosclerosis. The rate of VLDL-secretion from the liver is determined by its controlled transport from the endoplasmic reticulum (ER) to the Golgi. The ER-to-Golgi transport of newly synthesized VLDL is a complex multi-step process and is mediated by the VLDL transport vesicle (VTV). Once a nascent VLDL particle is synthesized in the lumen of the ER, it triggers the process of VTV-biogenesis and this process requires coat complex II (COPII) proteins that mediate the formation of classical protein transport vesicles (PTV). Even though, both VTV and PTV bud off the same ER at the same time and require the same COPII proteins, their cargos and sizes are different. The VTV specifically exports VLDL to the Golgi and excludes hepatic secretory proteins such as albumin and the size of the VTV is larger (~ 100 -120 nm) than PTV to accommodate VLDL-sized particles. These observations indicate (i) the existence of a sorting mechanism at the level of the ER; and (ii) the involvement of proteins in addition to COPII components. This doctoral thesis is focused on identification of proteins regulating VLDL sorting into the VTV and involved in the biogenesis of the VTV. In order to identify proteins present exclusively in VTV, we have characterized the proteome of VTV, which suggest CideB (cell death-inducing DFF45-like effector b) and SVIP (small VCP/P97 interacting protein) as candidates, present in VTV but excluded from PTV. We further confirmed the finding by performing co-immunoprecipitation studies and confocal microscopy studies. CideB, a 26-kDa protein was found to interact with apolipoprotein iv B100 (apoB 100), the structural protein of VLDL. Moreover, CideB interacts with two of the COPII components, Sar1 and Sec24. VTV generation was examined after blocking CideB by specific antibodies and by silencing CideB in rat primary hepatocytes. Knockdown of CideB in primary hepatocytes showed significant reduction in VTV generation, however, CideB was concentrated in VTV as compared with the ER suggesting its functional role in the sorting of VLDL into the VTV. SVIP, a small (~ 9-kDa) protein was found to interact with Sar1, a COPII component that initiates the budding of vesicles from ER membrane. SVIP has sites for myristoylation and we found increased recruitment of SVIP on ER membrane upon myristic acid (MA) treatment. Sar1 that lacks sites for myristoylation also is recruited more on ER upon myristoylation indicating that SVIP promotes Sar1 recruitment on ER. Additionally, our data suggest that Sar1 interacts with SVIP and forms a multimer that facilitates the biogenesis of VTV. Interestingly, silencing of SVIP reduced the VTV generation significantly. Conversely, incubation with MA increased the VTV budding, suggesting recruitment of SVIP on ER surface facilitates the VTV budding. We conclude that SVIP recruits Sar1 on ER membrane and makes an intricate COPII coat leading to the formation of a large vesicle, the VTV. Overall, the data presented in this thesis, determines the role of CideB and SVIP in regulating VLDL sorting and VTV biogenesis.

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京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第22832号 / 医博第4671号 / 新制||医||1047(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 林 康紀, 教授 安達 泰治, 教授 岩田 想 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Mitochondria are essential organelles for most eukaryotic cells, containing intricate networks of numerous proteins. These include, among others, complexes I-IV of the electron transport chain. Being at the crossroads of the tricarboxylic acid cycle and the respiratory chain, mitochondrial complex II plays a key role in cellular metabolism. The protein complex, also known as succinate dehydrogenase, is capable of not only succinate oxidation and electron transfer but also contributes to the production of reactive oxygen species. Mitochondrial complex II consists of four subunits, SDHA-D, and four dedicated protein assembly factors SDHAF1-4 that participate in complex II biogenesis. Mutations and epigenetic modulations of genes coding for succinate dehydrogenase subunits or assembly factors are associated with pathological conditions such as neurodegenerative diseases, or may result in tumor formation. However, inborn complex-II-linked mitochondrial pathologies are rather understudied, compared to diseases with causative errors of other mitochondrial complexes, presumably due to the fact that none of complex II subunits is encoded in the mitochondrial genome. Recent studies have shown that impairment of mitochondrial complex II function or assembly leads to accumulation of alternative assembly forms...

No description available.

Mitochondrial dysfunction has been implicated for a wide range of human diseases. One of the major biosynthetic processes in human mitochondria is the biogenesis of Iron-Sulfur (Fe-S) clusters which primarily involves in electron transfer reactions during oxidative phosphorylation (OXPHOS). Defects in Fe-S cluster biogenesis process leads to mitochondrial dysfunction and that eventually results in various human mitochondrial disorders. One of the major mitochondrial disorders associated with Fe-S cluster biogenesis impairment is exercise intolerance disorder ISCU myopathy, which is a result of loss of function of Fe-S cluster scaffold protein ISCU. Our biochemical results using yeast model system and HeLa cells lines suggests that ISCU Myopathy results in defective Fe-S cluster biogenesis in mitochondrial compartment. As a result, electron transport chain (ETC) complexes demonstrate significant reduction in their redox properties, leading to loss of cellular respiration. Furthermore, in ISCU Myopathy, mitochondria display enhancement in iron levels and reactive oxygen species, thereby causing oxidative stress leading to impairment in the mitochondrial functions. On the other hand, in mammalian mitochondria, the initial step of Fe-S cluster assembly process is assisted by NFS1-ISD11 complex, which delivers sulfur to the scaffold protein ISCU during Fe-S cluster synthesis. In humans, loss of ISD11 function leads to development of respiratory distress disorder, Combined Oxidative Phosphorylation Deficiency 19 (COXPD19). Our study maps the important ISD11 amino acid residues critical for in vivo Fe-S cluster biogenesis. Importantly, mutation of these critical ISD11 residues to alanine leads to its compromised interaction with NFS1, which results in reduced stability and enhanced aggregation of NFS1 in the mitochondria. Moreover, our findings highlight that, COXPD19 associated R68L ISD11 mutant displays reduced affinity to form a stable sub-complex with NFS1, thereby fails to prevent NFS1 aggregation, resulting impairment of Fe-S cluster biogenesis. The prime affected machinery is the ETC complex which demonstrates compromised redox properties, causing diminished mitochondrial respiration in COXPD19 patients. In summary, our findings provide compelling evidence that respiration defect due to impaired biogenesis of Fe-S clusters in ISCU myopathy patients, leads to manifestation of complex clinical symptoms. Additionally, our study highlights the role of ISD11 protein in Fe-S cluster biogenesis and maps the surface residues of ISD11 protein that are involved in interaction with sulfur donor protein NFS1. Moreover, we have demonstrated the molecular basis of disease progression of COXPD19 as a result of R68L ISD11 mutation.