Intracellular redistribution of acetyl-CoA, the pivotal point in differential susceptibility of cholinergic neurons and glial cells to neurodegenerative signals

Intramitochondrial decarboxylation of glucose-derived pyruvate by PDHC (pyruvate dehydrogenase complex) is a principal source of acetyl-CoA, for mitochondrial energy production and cytoplasmic synthetic pathways in all types of brain cells. The inhibition of PDHC, ACO (aconitase) and KDHC (ketoglutarate dehydrogenase complex) activities by neurodegenerative signals such as aluminium, zinc, amyloid β-peptide, excess nitric oxide (NO) or thiamine pyrophosphate deficits resulted in much deeper losses of viability, acetyl-CoA and ATP in differentiated cholinergic neuronal cells than in non-differentiated cholinergic, and cultured microglial or astroglial cell lines. In addition, in cholinergic cells, such conditions caused inhibition of ACh (acetylcholine) synthesis and its quantal release. Furthermore, cholinergic neuronal cells appeared to be resistant to high concentrations of LPS (lipopolysaccharide). In contrast, in microglial cells, low levels of LPS caused severalfold activation of NO, IL-6 (interleukin 6) and TNFα (tumour necrosis factor α) synthesis/release, accompanied by inhibition of PDHC, KDHC and ACO activities, and suppression of acetyl-CoA, but relatively small losses in their ATP contents and viability parameters. Compounds that protected these enzymes against inhibitory effects of neurotoxins alleviated acetyl-CoA and ATP deficits, thereby maintaining neuronal cell viability. These data indicate that preferential susceptibility of cholinergic neurons to neurodegenerative insults may result from competition for acetyl-CoA between mitochondrial energy-producing and cytoplasmic ACh-synthesizing pathways. Such a hypothesis is supported by the existence of highly significant correlations between mitochondrial/cytoplasmic acetyl-CoA levels and cell viability/transmitter functions respectively.

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An Aβ42 variant that inhibits intra- and extracellular amyloid aggregation and enhances cell viability

Biochemical Journal ◽

10.1042/bcj20180247 ◽

2018 ◽

Vol 475 (19) ◽

pp. 3087-3103 ◽

Cited By ~ 3

Author(s):

Ofek Oren ◽

Victor Banerjee ◽

Ran Taube ◽

Niv Papo

Keyword(s):

Amyloid Fibrils ◽

Neuronal Cells ◽

Amyloid Β ◽

Neuronal Cell ◽

Amyloid Β Peptide ◽

Cell Cytotoxicity ◽

Amyloid Aggregation ◽

Molar Ratios

Aggregation and accumulation of the 42-residue amyloid β peptide (Aβ42) in the extracellular matrix and within neuronal cells is considered a major cause of neuronal cell cytotoxicity and death in Alzheimer's disease (AD) patients. Therefore, molecules that bind to Aβ42 and prevent its aggregation are therapeutically promising as AD treatment. Here, we show that a non-self-aggregating Aβ42 variant carrying two surface mutations, F19S and L34P (Aβ42DM), inhibits wild-type Aβ42 aggregation and significantly reduces Aβ42-mediated cell cytotoxicity. In addition, Aβ42DM inhibits the uptake and internalization of extracellularly added pre-formed Aβ42 aggregates into cells. This was the case in both neuronal and non-neuronal cells co-expressing Aβ42 and Aβ42DM or following pre-treatment of cells with extracellular soluble forms of the two peptides, even at high Aβ42 to Aβ42DM molar ratios. In cells, Aβ42DM associates with Aβ42, while in vitro, the two soluble recombinant peptides exhibit nano-molar binding affinity. Importantly, Aβ42DM potently suppresses Aβ42 amyloid aggregation in vitro, as demonstrated by thioflavin T fluorescence and transmission electron microscopy for detecting amyloid fibrils. Overall, we present a new approach for inhibiting Aβ42 fibril formation both within and outside cells. Accordingly, Aβ42DM should be evaluated in vivo for potential use as a therapeutic lead for treating AD.

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Purification of the Chloroplast Pyruvate Dehydrogenase Complex from Spinach and Maize Mesophyll

Zeitschrift für Naturforschung C ◽

10.1515/znc-1986-11-1210 ◽

1986 ◽

Vol 41 (11-12) ◽

pp. 1011-1017 ◽

Cited By ~ 13

Author(s):

Hans-Jürgen Treede ◽

Klaus-Peter Heise

Keyword(s):

Pyruvate Dehydrogenase ◽

High Speed ◽

Pyruvate Dehydrogenase Complex ◽

Thiamine Pyrophosphate ◽

Partial Purification ◽

Reaction Products ◽

Acetyl Coa ◽

Aggregation State ◽

Dihydrolipoyl Dehydrogenase ◽

Dehydrogenase Complex

Abstract This paper deals with the partial purification of the pyruvate dehydrogenase complex (PDC) from chloroplasts of spinach and maize mesophyll which hitherto has been isolated only from pea chloroplasts. Starting with membrane free suspensions of lyophilized chloroplasts, and following a high-speed (140000 Xg) centrifugation of this “stromal extract”, the initial specific PDC-activities were concentrated by a factor 10 in the sediment. While most of the purification procedures described earlier resulted in almost complete loss of enzyme activities, a rate zonal sedimentation on linear glycerol gradients allowed for an additional up to 100-fold enrichment of the labile multienzyme complex, albeit with low yields. In contrast to chloroplast PDC from maize mesophyll, inactivation of the spinach complex during glycerol fractionation was due to the dissociation of its loosely bound dihydrolipoyl dehydrogenase component which collected in a lower density fraction of the gradient. Its recombination with PDC constituents of the bottom layer nearly restored initial activities. The chloroplast complex has been identified as true PDC by its substrate specificity for pyruvate, NAD+, and coenzyme A and the 1:1:1 stoichiometry of its reaction products NADH, CO2, and acetyl-CoA. The chloroplast PDC of both plant species showed the well known higher pH-and Mg-requirements than the mitochondrial complex. The observed species-specific differences in the stability of this multienzyme system suggest a connection with the aggregation state of its components. Apparently, the individual subcomplexes are able to function either together in acetyl-CoA formation or independently from each other, e.g. in the synthesis of acetolactate via hydroxy-ethyl-thiamine pyrophosphate or dihydrolipoyl dehydrogenase activities.

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Neurine, an acetylcholine autolysis product, elevates secreted amyloid-β protein precursor and amyloid-β peptide levels, and lowers neuronal cell viability in culture: A role in Alzheimer's disease?

Journal of Alzheimer s Disease ◽

10.3233/jad-2006-10102 ◽

2006 ◽

Vol 10 (1) ◽

pp. 9-16 ◽

Cited By ~ 8

Author(s):

David Tweedie ◽

Arnold Brossi ◽

DeMoa Chen ◽

Yuan-Wen Ge ◽

Jason Bailey ◽

...

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Cell Viability ◽

Amyloid Β ◽

Neuronal Cell ◽

Amyloid Β Peptide ◽

Amyloid Β Protein ◽

Protein Precursor ◽

Β Protein

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Evidence for existence of tissue-specific regulation of the mammalian pyruvate dehydrogenase complex

Biochemical Journal ◽

10.1042/bj3290191 ◽

1998 ◽

Vol 329 (1) ◽

pp. 191-196 ◽

Cited By ~ 345

Author(s):

Melissa M. BOWKER-KINLEY ◽

I. Wilhelmina DAVIS ◽

Pengfei WU ◽

A. Robert HARRIS ◽

M. Kirill POPOV

Keyword(s):

Tissue Distribution ◽

Pyruvate Dehydrogenase ◽

Pyruvate Dehydrogenase Complex ◽

Pyruvate Dehydrogenase Kinase ◽

Synthetic Analogue ◽

Complex Activity ◽

Acetyl Coa ◽

Tissue Specific ◽

Specific Regulation ◽

Dehydrogenase Complex

Tissue distribution and kinetic parameters for the four isoenzymes of pyruvate dehydrogenase kinase (PDK1, PDK2, PDK3 and PDK4) identified thus far in mammals were analysed. It appeared that expression of these isoenzymes occurs in a tissue-specific manner. The mRNA for isoenzyme PDK1 was found almost exclusively in rat heart. The mRNA for PDK3 was most abundantly expressed in rat testis. The message for PDK2 was present in all tissues tested but the level was low in spleen and lung. The mRNA for PDK4 was predominantly expressed in skeletal muscle and heart. The specific activities of the isoenzymes varied 25-fold, from 50 nmol/min per mg for PDK2 to 1250 nmol/min per mg for PDK3. Apparent Ki values of the isoenzymes for the synthetic analogue of pyruvate, dichloroacetate, varied 40-fold, from 0.2 mM for PDK2 to 8 mM for PDK3. The isoenzymes were also different with respect to their ability to respond to NADH and NADH plus acetyl-CoA. NADH alone stimulated the activities of PDK1 and PDK2 by 20 and 30% respectively. NADH plus acetyl-CoA activated these isoenzymes nearly 200 and 300%. Under comparable conditions, isoenzyme PDK3 was almost completely unresponsive to NADH, and NADH plus acetyl-CoA caused inhibition rather than activation. Isoenzyme PDK4 was activated almost 2-fold by NADH, but NADH plus acetyl-CoA did not activate above the level seen with NADH alone. These results provide the first evidence that the unique tissue distribution and kinetic characteristics of the isoenzymes of PDK are among the major factors responsible for tissue-specific regulation of the pyruvate dehydrogenase complex activity.

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Amyloid β-Peptide and Central Cholinergic Neurons: Involvement in Normal Brain Function and Alzheimer’s Disease Pathology

Abeta Peptide and Alzheimer’s Disease ◽

10.1007/978-1-84628-440-3_10 ◽

2006 ◽

pp. 159-178

Author(s):

Satyabrata Karn ◽

Z. Wei ◽

David MacTavish ◽

Doreen Kabogo ◽

Mee-Sook Song ◽

...

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Brain Function ◽

Amyloid Β ◽

Cholinergic Neurons ◽

Normal Brain ◽

Amyloid Β Peptide ◽

Normal Brain Function

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Tip60 protects against amyloid-β peptide-induced transcriptomic alterations via different modes of action in early versus late stages of neurodegenerative progression

10.1101/2020.06.09.142885 ◽

2020 ◽

Author(s):

Haolin Zhang ◽

Bhanu Chandra Karisetty ◽

Akanksha Bhatnagar ◽

Ellen M. Armour ◽

Mariah Beaver ◽

...

Keyword(s):

Cell Death ◽

Cognitive Deficits ◽

Late Stage ◽

Neurodegenerative Disorder ◽

Amyloid Β ◽

Neuronal Cell ◽

Amyloid Β Peptide ◽

Histone Deacetylase 2 ◽

Age Related ◽

Late Stages

ABSTRACTAlzheimer’s disease (AD) is an age-related neurodegenerative disorder hallmarked by amyloid-β (Aβ) plaque accumulation, neuronal cell death, and cognitive deficits that worsen during disease progression. Histone acetylation dysregulation, caused by an imbalance between reduced histone acetyltransferases (HAT) Tip60 and increased histone deacetylase 2 (HDAC2) levels, can directly contribute to AD pathology. However, whether such AD-associated neuroepigenetic alterations occur in response to Aβ peptide production and can be protected against by increasing Tip60 levels over the course of neurodegenerative progression remains unknown. Here we profile Tip60 HAT/HDAC2 dynamics and transcriptome-wide changes across early and late stage AD pathology in the Drosophila brain produced solely by human amyloid-β42. We show that early Aβ42 induction leads to disruption of Tip60 HAT/HDAC2 balance during early neurodegenerative stages preceding Aβ plaque accumulation that persists into late AD stages. Correlative transcriptome-wide studies reveal alterations in biological processes we classified as transient (early-stage only), late-onset (late-stage only), and constant (both). Increasing Tip60 HAT levels in the Aβ42 fly brain protects against AD functional pathologies that include Aβ plaque accumulation, neural cell death, cognitive deficits, and shorter life-span. Strikingly, Tip60 protects against Aβ42-induced transcriptomic alterations via distinct mechanisms during early and late stages of neurodegeneration. Our findings reveal distinct modes of neuroepigenetic gene changes and Tip60 neuroprotection in early versus late stages in AD that can serve as early biomarkers for AD, and support the therapeutic potential of Tip60 over the course of AD progression.

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TGF-β1 is a regulator of the pyruvate dehydrogenase complex in fibroblasts

Scientific Reports ◽

10.1038/s41598-020-74919-8 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Edward R. Smith ◽

Timothy D. Hewitson

Keyword(s):

Pyruvate Dehydrogenase ◽

Aerobic Glycolysis ◽

Pyruvate Dehydrogenase Complex ◽

Collagen I ◽

Acetyl Coa ◽

Fibroblast Activation ◽

Molecular Events ◽

Molecule Inhibitor ◽

Tgf Β1 ◽

Dehydrogenase Complex

Abstract TGF-β1 reprograms metabolism in renal fibroblasts, inducing a switch from oxidative phosphorylation to aerobic glycolysis. However, molecular events underpinning this are unknown. Here we identify that TGF-β1 downregulates acetyl-CoA biosynthesis via regulation of the pyruvate dehydrogenase complex (PDC). Flow cytometry showed that TGF-β1 reduced the PDC subunit PDH-E1α in fibroblasts derived from injured, but not normal kidneys. An increase in expression of PDH kinase 1 (PDK1), and reduction in the phosphatase PDP1, were commensurate with net phosphorylation and inactivation of PDC. Over-expression of mutant PDH-E1α, resistant to phosphorylation, ameliorated effects of TGF-β1, while inhibition of PDC activity with CPI-613 was sufficient to induce αSMA and pro-collagen I expression, markers of myofibroblast differentiation and fibroblast activation. The effect of TGF-β1 on PDC activity, acetyl-CoA, αSMA and pro-collagen I was also ameliorated by sodium dichloroacetate, a small molecule inhibitor of PDK. A reduction in acetyl-CoA, and therefore acetylation substrate, also resulted in a generalised loss of protein acetylation with TGF-β1. In conclusion, TGF-β1 in part regulates fibroblast activation via effects on PDC activity.

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Molecular biology of acetyl-CoA metabolism

Biochemical Society Transactions ◽

10.1042/bst0280591 ◽

2000 ◽

Vol 28 (6) ◽

pp. 591-593 ◽

Cited By ~ 11

Author(s):

B. J. Nikolau ◽

D. J. Oliver ◽

P. S. Schnable ◽

E. S. Wurtele

Keyword(s):

Pyruvate Dehydrogenase ◽

Pyruvate Dehydrogenase Complex ◽

Pyruvate Decarboxylase ◽

Acetyl Coa Carboxylase ◽

Atp Citrate Lyase ◽

Acetyl Coa ◽

Acetaldehyde Dehydrogenase ◽

Citrate Lyase ◽

Biochemical Genetic ◽

Dehydrogenase Complex

We have characterized the expression of potential acetyl-CoA-generating genes (acetyl-CoA synthetase, pyruvate decarboxylase, acetaldehyde dehydrogenase, plastidic pyruvate dehydrogenase complex and ATP-citrate lyase), and compared these with the expression of acetyl-CoA-metabolizing genes (heteromeric and homomeric acetyl-CoA carboxylase). These comparisons have led to the development of testable hypotheses as to how distinct pools of acetyl-CoA are generated and metabolized. These hypotheses are being tested by combined biochemical, genetic and molecular biological experiments, which is providing insights into how acetyl-CoA metabolism is regulated.

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