Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.24.64 (MPP)
 1,876 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

N-Methylated beta-carbolinium compounds (N-Me-BCs), including 2-N-methyl and 2,9-N,N-dimethyl analogs, structural analogs of 1-methyl-4-phenylpyridinium (MPP+), may be endogenously bioactivated, MPP(+)-like toxins, capable of inducing parkinsonism. Both MPP+ and selected N-Me-BCs inhibit NADH-linked mitochondrial respiration (Complex I). We now show that both also inhibit succinate-supported (Complex II) respiration, the greatest inhibition (80%) being seen for 2,9-dimethylharmanium. Complex I inhibition occurs at MPP+ concentrations (IC50 = 0.17 mM) about one order of magnitude lower than Complex II inhibition (greater than 1.2 mM). In contrast, Complex I and Complex II inhibition by the N-Me-BCs tested occurred at similar concentrations (I, 0.1 mM; II, 0.25 mM) and concentrations similar to Complex I inhibition by MPP+. 2,9-N,N-Dimethyl-BCs, which are the permanently charged BC analogs of MPP+, show inhibitory characteristics similar to MPP+: slow onset of inhibition, potentiation by TPB, and reversal by DNP. The fact that succinate oxidation cannot bypass the Complex II inhibition by N-Me-BCs could enhance any chronic neurotoxicity of N-Me-BCs.
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PMID:Inhibition of mitochondrial succinate oxidation--similarities and differences between N-methylated beta-carbolines and MPP+. 131 43

The gene encoding the yeast mitochondrial rotenone-insensitive internal NADH: ubiquinone-6 oxidoreductase has been sequenced. The DNA sequence indicates the presence of an open reading frame of 1539 bp predicted to encode a protein of 513 amino acid residues (57.2 kDa). The NADH dehydrogenase is synthesized as a precursor protein containing a signal sequence of 26 residues. In vitro import experiments show that the precursor NADH dehydrogenase is cleaved to the mature size by the matrix processing peptidase. Both cleavage and translocation across the mitochondrial membrane(s) are dependent on the membrane potential component of the proton-motive force. Comparison of the protein sequence of the yeast NADH dehydrogenase with the data bank indicates that the enzyme from yeast is homologous to the NADH dehydrogenase of Escherichia coli (22.2% identical residues). Both NADH dehydrogenases contain in the central part of the protein a sequence predicted to fold into a beta alpha beta structure involved in the binding of NADH or FAD(H2). Various aspects of the protein structure are discussed.
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PMID:Primary structure and import pathway of the rotenone-insensitive NADH-ubiquinone oxidoreductase of mitochondria from Saccharomyces cerevisiae. 173 44

The primary structure of a 40 kDa subunit of the respiratory chain NADH:ubiquinone reductase from Neurospora crassa was determined by sequencing cDNA, genomic DNA and the N-terminus of the mature protein. The gene which is interrupted by 7 introns encodes a preprotein consisting of 375 amino acids with a 26 amino acid long presequence typical for a mitochondrial targeting signal. The sequence of the mature subunit shows conspicuous similarities to the recently [(1989) Nature 339, 147-149] discovered protein family which includes subunits I and II of the ubiquinol:cytochrome c reductase, and the processing proteins, matrix processing peptidase and processing enhancing protein, of mitochondria. The possible role of the subunit is discussed.
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PMID:Relationship between a subunit of NADH dehydrogenase (complex I) and a protein family including subunits of cytochrome reductase and processing protease of mitochondria. 182 2

The primary structure of the nuclear-encoded 18.3 kDa subunit of the respiratory chain NADH: ubiquinone reductase (complex I) from Neurospora crassa was determined by sequencing cDNA and the N-terminus of the protein. The cDNA contains an open reading frame for a protein of 206 amino acids. The mature protein consists of 173 amino acids and has a molar mass of 18,341 Da. The precursor protein includes a characteristic mitochondrial import sequence with a typical matrix peptidase processing site.
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PMID:Primary structure of the nuclear-encoded 18.3 kDa subunit of NADH: ubiquinone reductase (complex I) from Neurospora crassa mitochondria. 183 Apr 90

Earlier studies from our laboratory have demonstrated that 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) toxicity could be modulated by inhibitors and inducer of cytochrome P450 (P450) in an in vitro model consisting of sagittal slices of mouse brain. To understand the molecular mechanisms underlying the role of P450 on MPTP toxicity, it was undertaken to study the effect of the modulators of P450 on the toxicity of the metabolite of MPTP, namely, 1-methyl-4-phenylpyridinium ion (MPP+). Incubation of mouse brain slices with various concentrations of MPP+ (1-100 microM) resulted in dose-dependent inhibition of mitochondrial enzyme NADH-dehydrogenase (NADH-DH) and leakage of the cytosolic enzyme lactate dehydrogenase from the slice into the medium. MPP(+)-induced toxicity was abolished by pretreatment of the slices with inhibitors of monoamine oxidase (MAO; pargyline and deprenyl) or inhibitors of P450 (piperonyl butoxide or SKF-525A) or dopamine uptake blocker (GBR-12909), as measured by the activity of NADH-DH in slices and leakage of lactate dehydrogenase from the slice into the medium. Slices prepared from mice pretreated with phenobarbital (an inducer of P450) potentiated the toxic effects of MPP+. Pretreatment of slices with MAO-inhibitor, P450 inhibitors, or dopamine uptake blocker attenuated the uptake of MPP+ into the slices. In contrast, MPP+ uptake was significantly increased in slices prepared from phenobarbital-pretreated mice. Thus, both MAO and P450 inhibitors abolish the toxicity of MPP+ in the sagittal slices of mouse brain by altering the uptake of the toxin into the slices.
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PMID:Protection and potentiation of 1-methyl-4-phenylpyridinium-induced toxicity by cytochrome P450 inhibitors and inducer may be due to the altered uptake of the toxin. 786 Nov 52

N-methyl-4-phenylpyridinium (MPP+), the neurotoxic metabolite of N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, kills dopaminergic neurons after its accumulation in mitochondria where it inhibits Complex I of the respiratory chain. MPP+ inhibits respiration by binding to both a hydrophobic and a hydrophilic site on Complex I and this inhibition is increased by the lipophilic tetraphenylboron anion (TPB-) which facilitates movement of MPP+ through membranes and its penetration to the hydrophobic binding site on Complex I. To investigate the inhibition of respiration by MPP(+)-like compounds, we have measured simultaneously NADH-linked mitochondrial respiration and the uptake and accumulation of the N-benzyl-4-styrylpyridinium and N-ethyl-4-styrylpyridinium cations in mitochondria using ion-selective electrodes. The data provide direct evidence that TPB- increases the inhibition not by increasing matrix concentration but by facilitating access to the inhibitory sites on Complex I. We have also compared the rates of uptake of MPP+ analogues of varied lipophilicity by the inner membrane and the development of inhibition of NADH oxidation, using an inverted mitochondrial inner membrane preparation and appropriate ion-selective electrodes. These experiments demonstrated that the amount of MPP+ analogue bound to the inner membrane greatly exceeded the quantity required for complete inhibition of NADH oxidation. Moreover, binding to the membrane occurred much more rapidly than the development of inhibition with all MPP+ analogues tested. This suggests that the attainment of a correct orientation of these compounds within the membrane and the binding site may be a rate-limiting step in the development of inhibition.
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PMID:Inhibition of complex I by hydrophobic analogues of N-methyl-4-phenylpyridinium (MPP+) and the use of an ion-selective electrode to measure their accumulation by mitochondria and electron-transport particles. 788 89

It is now generally accepted that the nigrostriatal degenerative properties of the parkinsonian-inducing agent 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine are mediated by the brain monoamine oxidase B generated 1-methyl-4-phenylpyridinium metabolite (MPP+). In this article, the results are described of ongoing efforts to evaluate the MPP(+)-type neurotoxic potential of the haloperidol (HP)-derived pyridinium metabolite HPP+, a 1,4-disubstituted structural analog of MPP+, which is formed in humans and rats treated with HP. Previous studies in the rat have shown that intrastriatal perfusion of HPP+ leads to the irreversible depletion of striatal dopamine and serotonin. Furthermore, HPP+ was a potent inhibitor of NADH-supported mitochondrial respiration. This article reports that HPP+ also is toxic to dopaminergic and serotonergic neurons in cultures of embryonic mesencephalic cells, as measured by loss of the ability of exposed cells to accumulate tritium-labeled dopamine and serotonin and by immunochemical staining techniques. HPP+ also inhibited the uptake of these labeled neurotransmitters by synaptosomes prepared from mouse neostriata (dopamine) and cortical tissues (serotonin). Because HP is unlikely to be a substrate for brain monoamine oxidase B, the production and accumulation of HPP+ in the brain is probably not comparable to that of MPP+. On the other hand, chronic exposure to HP could result in brain levels of this lipophilic quaternary pyridinium species that might coincide with the late-appearing tardive dyskinesias that are observed in some HP-treated patients months and, more often, years after the initiation of HP therapy.
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PMID:1-Methyl-4-phenylpyridinium-like neurotoxicity of a pyridinium metabolite derived from haloperidol: cell culture and neurotransmitter uptake studies. 807 74

MPP+ has been reported to inhibit reduced nicotinamide adenine dinucleotide (NADH) dehydrogenase in mitochondria, which results in the formation of O2(.-). The current report demonstrates that H2O2 and HO. are also products of MPP+ interaction with NADH dehydrogenase. It is possible that MPP. formation precedes the formation of some of these active oxygen species. Reducing equivalents for radical formation come from NADH. MPP+ may be capable of interacting with submitochondrial particles at a site other than the rotenone site, which results in some formation of oxygen radicals. Plasma amine oxidase incubations with MPDP+ resulted in O2.- H2O2, and perhaps HO. formation. This is probably due to MPP. formation from the oxidation of MPDP+. This study presents new findings that indicate the potential importance of oxygen radical formation in mitochondria during MPTP toxicity.
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PMID:MPP+ and MPDP+ induced oxygen radical formation with mitochondrial enzymes. 839 43

The endogenous neurotoxin 1-methyl-6,7-dihydroxy-1,2,3, 4-tetrahydroisoquinoline (salsolinol), which is structurally similar to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), has been reported to inhibit mitochondrial complex I (NADH-Q reductase) activity as does the MPTP metabolite 1-methyl-4-phenylpyridinium ion (MPP(+)). However, the mechanism of salsolinol leading to neuronal cell death is still unknown. Thus, we correlated indices of cellular energy production and cell viability in human dopaminergic neuroblastoma SH-SY5Y cells after exposure to salsolinol and compared these results with data obtained with MPP(+). Both toxins induce time and dose-dependent decrease in cell survival with IC(50) values of 34 microM and 94 microM after 72 h for salsolinol and MPP(+), respectively. Furthermore, salsolinol and MPP(+) produce a decrease of intracellular net ATP content with IC(50) values of 62 microM and 66 microM after 48 h, respectively. In contrast to MPP(+), salsolinol does not induce an increase of intracellular net NADH content. In addition, enhancing glycolysis by adding D-glucose to the culture medium protects the cells against MPP(+) but not salsolinol induced cellular ATP depletion and cytotoxicity. These results suggest that cell death induced by salsolinol is due to impairment of cellular energy supply, caused in particular by inhibition of mitochondrial complex II (succinate-Q reductase), but not complex I.
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PMID:1-Methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline (salsolinol) is toxic to dopaminergic neuroblastoma SH-SY5Y cells via impairment of cellular energy metabolism. 1065 Jan 31

Riluzole is neuroprotective in patients with amyotrophic lateral sclerosis and may also protect dopamine (DA) neurons in Parkinson's disease. We examined the neuroprotective potential of riluzole on DA neurons using primary rat mesencephalic cultures and human dopaminergic neuroblastoma SH-SY5Y cells. Riluzole (up to 10 microM:) alone affected neither the survival of DA neurons in primary cultures nor the growth of SH-SY5Y cells after up to 72 h. Riluzole (1-10 microM:) dose-dependently reduced DA cell loss caused by exposure to MPP(+) in both types of cultures. These protective effects were accompanied by a dose-dependent decrease of intracellular ATP depletion caused by MPP(+) (30-300 microM:) in SH-SY5Y cells without affecting intracellular net NADH content, suggesting a reduction of cellular ATP consumption rather than normalization of mitochondrial ATP production. Riluzole (1-10 microM:) also attenuated oxidative injury in both cell types induced by exposure to L-DOPA and 6-hydroxydopamine, respectively. Consistent with its antioxidative effects, riluzole reduced lipid peroxidation induced by Fe(3+) and L-DOPA in primary mesencephalic cultures. Riluzole (10 microM) did not alter high-affinity uptake of either DA or MPP(+). However, in the same cell systems, riluzole induced neuronal and glial cell death with concentrations higher than those needed for maximal protective effects (> or =100 microM:). These data demonstrate that riluzole has protective effects on DA neurons in vitro against neuronal injuries induced by (a) impairment of cellular energy metabolism and/or (b) oxidative stress. These results provide further impetus to explore the neuroprotective potential of riluzole in Parkinson's disease.
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PMID:Protective effects of riluzole on dopamine neurons: involvement of oxidative stress and cellular energy metabolism. 1108 Jan 77


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