Inositol trisphosphate 3-kinase B is increased in human Alzheimer brain and exacerbates mouse Alzheimer pathology
; ; et al
in Brain : A Journal of Neurology (2014), 137
S. Schurmans and J.-P. Brion contributed equally to this work Corresponding author: S. Schurmans, Laboratoire de Génétique Fonctionnelle, GIGA-Research Centre, Building 34, Université de Liège, rue de ... [more ▼]
S. Schurmans and J.-P. Brion contributed equally to this work Corresponding author: S. Schurmans, Laboratoire de Génétique Fonctionnelle, GIGA-Research Centre, Building 34, Université de Liège, rue de l’Hôpital 1, 4000-Liège, Belgium. Abstract: Inositol (1,4,5) trisphosphate 3-kinase B phosphorylates inositol 1,4,5-trisphosphate into inositol 1,3,4,5-tetrakisphosphate and controls signal transduction in various hematopoietic cells. Surprisingly, it has been reported that Inositol (1,4,5) trisphosphate 3-kinase B mRNA level is significantly increased in the cerebral cortex of Alzheimer patients, compared to control subjects. Since Extracellular signal-regulated kinases 1/2 activation is increased in Alzheimer brain and since Inositol (1,4,5) trisphosphate 3-kinase B is a regulator of Extracellular signal-regulated kinases 1/2 activation in some hematopoietic cells, we tested whether this increased activation in Alzheimer’s disease might be related to an increased activity of Inositol (1,4,5) trisphosphate 3-kinase B. We show here that Inositol (1,4,5) trisphosphate 3-kinase B protein level was 3 fold increased in the cerebral cortex of most Alzheimer patients, compared to control subjects, and accumulated in dystrophic neurites associated to amyloid plaques. In mouse Neuro-2a neuroblastoma cells, Inositol (1,4,5) trisphosphate 3-kinase B overexpression was associated with increased cell apoptosis and increased β-secretase 1 activity leading to amyloid-β peptides overproduction. In this cellular model, an inhibitor of Mitogen-activated kinase kinases 1/2 completely prevented amyloid-β peptides overproduction. Transgenic overexpression of Inositol (1,4,5) trisphosphate 3-kinase B in mouse forebrain neurons was not sufficient to induce amyloid plaques formation or TAU hyperphosphorylation. However, in the 5X Familial Alzheimer’s Disease mouse model, neuronal Inositol (1,4,5) trisphosphate 3-kinase B overexpression significantly increased Extracellular signal-regulated kinases 1/2 activation and β-secretase 1 activity, resulting in exacerbated Alzheimer pathology as shown by increased astrogliosis, amyloid-β40 peptide production and TAU hyperphosphorylation. No impact on pathology was observed in the 5X Familial Alzheimer’s Disease mouse model when a catalytically inactive Inositol (1,4,5) trisphosphate 3-kinase B protein was overexpressed. Together, our results point to the Inositol (1,4,5) trisphosphate 3-kinase B /Inositol 1,3,4,5-tetrakisphosphate/Extracellular signal-regulated kinases 1/2 signaling pathway as an important regulator of neuronal cell apoptosis, Amyloid precursor protein processing and TAU phosphorylation in Alzheimer’s disease, and suggest that Inositol (1,4,5) trisphosphate 3-kinase B could represent a new target for reducing pathology in human AD patients with increased cortical Inositol (1,4,5) trisphosphate 3-kinase B expression. [less ▲]Detailed reference viewed: 32 (14 ULg)
Overexpression of a novel member of the mitochondrial carrier family rescues defects in both DNA and RNA metabolism in yeast mitochondria.
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in Molecular & General Genetics [=MGG] (1995), 246
The PIF1 and MRS2 gene products have previously been shown to be essential for mitochondrial DNA maintenance at elevated temperatures and mitochondrial group II intron splicing, respectively, in the yeast ... [more ▼]
The PIF1 and MRS2 gene products have previously been shown to be essential for mitochondrial DNA maintenance at elevated temperatures and mitochondrial group II intron splicing, respectively, in the yeast Saccharomyces cerevisiae. A multicopy suppressor capable of rescuing the respiratory deficient phenotype associated with null alleles of either gene has been isolated. This suppressor is a nuclear gene that was called RIM2/MRS12. The RIM2/MRS12 gene encodes a predicted protein of 377 amino acids that is essential for mitochondrial DNA metabolism and proper cell growth. Inactivation of this gene causes the total loss of mitochondrial DNA and, compared to wild-type rhoo controls, a slow-growth phenotype on media containing glucose. Analysis of the RIM2/MRS12 protein sequence suggests that RIM2/MRS12 encodes a novel member of the mitochondrial carrier family. In particular, a typical triplicate structure, where each repeat consists of two putative transmembrane segments separated by a hydrophilic loop, can be deduced from amino acid sequence comparisons and the hydropathy profile of RIM2/MRS12. Antibodies directed against the aminoterminus of RIM2/MRS12 detect this protein in mitochondria. The function of the RIM2/MRS12 protein and the substrates it might transport are discussed. [less ▲]Detailed reference viewed: 14 (1 ULg)
Effect of aspartate and glutamate on the oxoglutarate carrier investigated in rat heart mitochondria and inverted submitochondrial vesicles.
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in Biochimica et Biophysica Acta-Bioenergetics (1994), 1185
Interaction of glutamate and aspartate with the oxoglutarate carrier was investigated in rat heart mitochondria or inverted submitochondrial particles. With mitochondria, glutamate and aspartate had no ... [more ▼]
Interaction of glutamate and aspartate with the oxoglutarate carrier was investigated in rat heart mitochondria or inverted submitochondrial particles. With mitochondria, glutamate and aspartate had no effect on the initial rate of oxoglutarate or malate uptake. With inverted submitochondrial vesicles, binding experiments indicated that aspartate bound to the oxoglutarate carrier on its matricial face and increased the affinity of the substrate binding site for malate but did not change the affinity for oxoglutarate. Glutamate had no effect on both substrate bindings. The dissociation constants of the binary substrate-carrier complexes on the matricial side were determined (1.28 +/- 0.15 mM for oxoglutarate and 2.22 +/- 0.26 mM for malate). These values, compared with those obtained previously on the cytosolic side of intact mitochondria, confirmed the asymmetry of the carrier in the native membrane (higher affinities on the cytosolic face). It is concluded that (1) aspartate and glutamate are not cytosolic effectors of the oxoglutarate carrier, (2) matricial aspartate is a positive effector of the binding of malate on the matricial side of the oxoglutarate carrier, and (3) such a characteristic may play a role in the regulation of the oxoglutarate carrier. Thus, it may be emphasized that (1) this observation is the first clear evidence of a well-defined 'sophisticated regulation' (allosteric) of a mitochondrial metabolite carrier, and (2) this regulation of the oxoglutarate carrier may have important consequences on the efficiency of reducing equivalent import in the matrix space by the malate-aspartate shuttle. [less ▲]Detailed reference viewed: 10 (1 ULg)
Biochemical, genetic and molecular characterization of new respiratory-deficient mutants in Chlamydomonas reinhardtii.
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in Plant Molecular Biology (1992), 18
Eight respiratory-deficient mutants of Chlamydomonas reinhardtii have been isolated after mutagenic treatment with acriflavine or ethidium bromide. They are characterized by their inability to grow or ... [more ▼]
Eight respiratory-deficient mutants of Chlamydomonas reinhardtii have been isolated after mutagenic treatment with acriflavine or ethidium bromide. They are characterized by their inability to grow or their very reduced growth under heterotrophic conditions. One mutation (Class III) is of nuclear origin whereas the seven remaining mutants (Classes I and II) display a predominantly paternal mt- inheritance, typical of mutations residing in the mitochondrial DNA. Biochemical analysis has shown that all mutants are deficient in the cyanide-sensitive cytochrome pathway of the respiration whereas the alternative pathway is still functional. Measurements of complexes II + III (antimycin-sensitive succinate-cytochrome c oxido-reductase) and complex IV (cytochrome c oxidase) activities allowed to conclude that six mutations have to be localized in the mitochondrial apocytochrome b (COB) gene, one in the mitochondrial cytochrome oxidase subunit I (COI) gene and one in a nuclear gene encoding a component of the cytochrome oxidase complex. By using specific probes, we have moreover demonstrated that five mutants (Class II mutants) contain mitochondrial DNA molecules deleted in the terminal end containing the COB gene and the telomeric region; they also possess dimeric molecules resulting from end-to-end junctions of deleted monomers. The two other mitochondrial mutants (Class I) have no detectable gross alteration. Class I and Class II mutants can also be distinguished by the pattern of transmission of the mutation in crosses. An in vivo staining test has been developed to identify rapidly the mutants impaired in cyanide-sensitive respiration. [less ▲]Detailed reference viewed: 18 (1 ULg)
Kinetic study of the aspartate/glutamate carrier in intact rat heart mitochondria and comparison with a reconstituted system.
Sluse, Francis ; ; et al
in Biochimica et Biophysica Acta-Bioenergetics (1991), 1058
The homologous exchange of external [14C] aspartate/internal aspartate catalyzed by the aspartate/glutamate carrier of rat heart mitochondria was investigated using aspartate-loaded, glutamate-depleted ... [more ▼]
The homologous exchange of external [14C] aspartate/internal aspartate catalyzed by the aspartate/glutamate carrier of rat heart mitochondria was investigated using aspartate-loaded, glutamate-depleted mitochondria. An inhibitor-stop technique was developed for kinetic studies by applying pyridoxal phosphate. Direct initial rate determinations from the linear phase of [14C] aspartate uptake were insufficiently accurate at high external and/or low internal substrate concentrations. Therefore, the full time-course of [14C] aspartate uptake until reaching isotope equilibrium was fitted by a single exponential function and was used to calculate reliable initial steady-state rates. This method was applied in bisubstrate analyses of the antiport reaction for different external and internal aspartate concentrations. The kinetic patterns obtained in double reciprocal plots showed straight lines converging on the abscissa. This result is consistent with a sequential antiport mechanism. It implies the existence of a catalytic ternary complex that is formed by the translocator and substrate molecules bound from both sides of the membrane. The Km values for aspartate were clearly different for the external and the internal sides of the membrane, 216 +/- 23 microM and 2.4 +/- 0.5 mM, respectively. These values indicated a definite transmembrane asymmetry of the carrier. The same asymmetry became evident when investigating the isolated protein from bovine heart mitochondria after reconstitution into liposomes. In this case the Km values for external and internal aspartate were determined to be 123 +/- 11 microM and 2.8 +/- 0.6 mM, respectively. This comparison demonstrates a right-side out orientation of the carrier after insertion into liposomal membranes. The sequential transport mechanism of the aspartate/glutamate carrier, elucidated both in proteoliposomes and in mitochondria, also seems to be a common characteristic of other mitochondrial antiport carriers [less ▲]Detailed reference viewed: 14 (3 ULg)