Regulation of <i>N</i>‐acetylaspartate and <i>N</i>‐acetylaspartylglutamate biosynthesis by protein kinase activators

Arun, Peethambaran; Madhavarao, Chikkathur N.; Moffett, John R.; Namboodiri, M. A. A.

doi:10.1111/j.1471-4159.2006.04068.x

Cited by 63 publications

(42 citation statements)

References 35 publications

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“…NAAG synthesis from radiolabeled amino acids is insensitive to inhibition of protein synthesis as demonstrated both in spinal sensory ganglia in vivo (11) or in isolated spinal cords (12). Furthermore, labeling studies in vivo (24), in spinal cords (12) and in SH-SY5Y human neuroblastoma cells (25) all indicate that NAA is a better precursor for NAAG than free aspartate. Finally, almost four decades ago Reichelt and Kvamme (19) demonstrated the existence of NAAG synthesis in homogenates of mouse brain and showed it to be absolutely dependent on the presence of ATP.…”

Section: Agreement With Previous Results Suggesting That Naag Ismentioning

confidence: 88%

Molecular Identification of N-Acetylaspartylglutamate Synthase and β-Citrylglutamate Synthase

Collard

Stroobant

Lamosa

et al. 2010

Journal of Biological Chemistry

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The purpose of the present work was to determine the identity of the enzymes that synthesize N-acetylaspartylglutamate (NAAG), the most abundant dipeptide present in vertebrate central nervous system (CNS), and ␤-citrylglutamate, a structural analogue of NAAG present in testis and immature brain. Previous evidence suggests that NAAG is not synthesized on ribosomes but presumably is synthesized by a ligase. As attempts to detect this ligase in brain extracts failed, we searched the mammalian genomes for putative enzymes that could catalyze this type of reaction. Mammalian genomes were found to encode two putative ligases homologous to Escherichia coli RIMK, which ligates glutamates to the C terminus of ribosomal protein S6. One of them, named RIMKLA, is almost exclusively expressed in the CNS, whereas RIMKLB, which shares 65% sequence identity with RIMKLA, is expressed in CNS and testis. Both proteins were expressed in bacteria or HEK293T cells and purified. RIMKLA catalyzed the ATP-dependent synthesis of N-acetylaspartylglutamate from N-acetylaspartate and L-glutamate. RIMKLB catalyzed this reaction as well as the synthesis of ␤-citrylglutamate. The nature of the reaction products was confirmed by mass spectrometry and NMR. RIMKLA was shown to produce stoichiometric amounts of NAAG and ADP, in agreement with its belonging to the ATP-grasp family of ligases. The molecular identification of these two enzymes will facilitate progress in the understanding of the function of NAAG and ␤-citrylglutamate. N-Acetylaspartylglutamate (NAAG),3 the most abundant dipeptide in the CNS, is present in brain and in the spinal cord, most particularly in neurons of the anterior horn (1). NAAG can be released from neurons upon calcium depolarization (reviewed in Ref. 1) and is a substrate for two glial peptidases, glutamate carboxypeptidase-II (2) and, to a lower extent, glutamate carboxypeptidase-III (3), which are anchored to the plasma membrane with their catalytic site oriented toward the outside of the cell. NAAG long has been thought to be a neurotransmitter able to bind to the metabotropic glutamate receptors mGluR3 (4). Two recent reports suggest, however, that the effects of NAAG as a neurotransmitter are due to a 0.5% glutamate contamination present in commercial NAAG (5, 6). The function of NAAG is, therefore, presently unknown.␤-Citrylglutamate (BCG), which is structurally close to NAAG, is less well characterized. It was first identified in newborn rat brain, where its concentration reaches 0.5-1 mol/g at birth and then decreases with age (7). BCG also was detected in kidneys and heart and to a much lower extent in intestine, spinal cord, and lung of newborn rats. The content of BCG in all organs decreased with age to the noticeable exception of testes, where its concentration increases during sexual maturation and remains constant in adulthood (8,9). BCG is present not only in the testes of mammals but also in those of amphibians and fishes. There is evidence in germinal cells for a role in spermatogenesis (9). BCG rec...

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Section: Agreement With Previous Results Suggesting That Naag Ismentioning

confidence: 88%

Molecular Identification of N-Acetylaspartylglutamate Synthase and β-Citrylglutamate Synthase

Collard

Stroobant

Lamosa

et al. 2010

Journal of Biological Chemistry

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“…It is synthesized enzymatically from NAA and glutamate (Arun et al, 2006;Boltshauser et al, 2004;Cangro et al, 1987;Gehl et al, 2004) and is localized in specific types of neurons throughout the CNS (Anderson et al, 1987;Moffett et al, 1993;Moffett and Namboodiri, 1995;Tieman et al, 1991;Tieman and Tieman, 1996). NAAG is released from synapses in a calcium dependent manner (Williamson et al, 1991), and acts through presynaptic metabotropic glutamate receptors to modulate the release of classical neurotransmitters (Xi et al, 2002;Zhao et al, 2001).…”

Section: Naa and Naag Biosynthesismentioning

confidence: 99%

“…The presence of a "NAAG synthetase" enzyme has been postulated based on indirect means in several studies (Arun et al, 2006;Cangro et al, 1987;Gehl et al, 2004;Urazaev et al, 2001;Williamson and Neale, 1988). Most recent studies which have successfully demonstrated NAAG biosynthesis were done in neural explants, including excised rat dorsal root ganglia (Cangro et al, 1987), excised frog retinas (Williamson and Neale, 1988), crayfish nerve cord (Urazaev et al, 2001) and hemisected rat spinal cord (Gehl et al, 2004).…”

Section: Evidence For a Naag Synthetase Enzymementioning

confidence: 99%

“…Most recent studies which have successfully demonstrated NAAG biosynthesis were done in neural explants, including excised rat dorsal root ganglia (Cangro et al, 1987), excised frog retinas (Williamson and Neale, 1988), crayfish nerve cord (Urazaev et al, 2001) and hemisected rat spinal cord (Gehl et al, 2004). In several recent reports, NAAG biosynthesis has been observed in cell culture, including primary rat astrocyte cell culture (Gehl et al, 2004), and in a continuous human neuroblastoma cell line (Arun et al, 2004;Arun et al, 2006).…”

Section: Evidence For a Naag Synthetase Enzymementioning

confidence: 99%

“…Recently, Arun and coworkers have shown in a continuous human neuroblastoma cell line (SH-SY5Y) that the addition of unlabeled NAA to the culture media resulted in a dosedependent increase in NAAG synthesis from radiolabeled precursors (Arun et al, 2006). The average endogenous NAA level in SH-SY5Y cells was about 824 ng/mg protein, and these levels increased to about 1869 ng/mg protein in cells exposed to 10 mM external NAA representing an approximately 2.2-fold increase in intracellular NAA.…”

Section: Naa Concentration Increases Naag Biosynthesis-the Evidence Tmentioning

confidence: 99%

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N-Acetylaspartate in the CNS: From neurodiagnostics to neurobiology

Moffett

Ross

Arun

et al. 2007

Progress in Neurobiology

1,230

1,126

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The brain is unique among organs in many respects, including its mechanisms of lipid synthesis and energy production. The nervous system-specific metabolite N-acetylaspartate (NAA), which is synthesized from aspartate and acetyl-coenzyme A in neurons, appears to be a key link in these distinct biochemical features of CNS metabolism. During early postnatal CNS development, the expression of lipogenic enzymes in oligodendrocytes, including the NAA-degrading enzyme aspartoacylase (ASPA), is increased along with increased NAA production in neurons. NAA is transported from neurons to the cytoplasm of oligodendrocytes, where ASPA cleaves the acetate moiety for use in fatty acid and steroid synthesis. The fatty acids and steroids produced then go on to be used as building blocks for myelin lipid synthesis. Mutations in the gene for ASPA result in the fatal leukodystrophy Canavan disease, for which there is currently no effective treatment. Once postnatal myelination is completed, NAA may continue to be involved in myelin lipid turnover in adults, but it also appears to adopt other roles, including a bioenergetic role in neuronal mitochondria. NAA and ATP metabolism appear to be linked indirectly, whereby acetylation of aspartate may facilitate its removal from neuronal mitochondria, thus favoring conversion of glutamate to alpha ketoglutarate which can enter the tricarboxylic acid cycle for energy production. In its role as a mechanism for enhancing mitochondrial energy production from glutamate, NAA is in a key position to act as a magnetic resonance spectroscopy marker for neuronal health, viability and number. Evidence suggests that NAA is a direct precursor for the enzymatic synthesis of the neuron specific dipeptide N-acetylaspartylglutamate, the most concentrated neuropeptide in the human brain. Other proposed roles for NAA include neuronal osmoregulation and axon-glial signaling. We propose that NAA may also be involved in brain nitrogen balance. Further research will be required to more fully understand the biochemical functions served by NAA in CNS development and activity, and additional functions are likely to be discovered.

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3D magnetic resonance spectroscopic imaging reveals links between brain metabolites and multidimensional pain features in fibromyalgia

Lee

Andronesi

Torrado‐Carvajal

et al. 2021

European Journal of Pain

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Background: Fibromyalgia is a centralized multidimensional chronic pain syndrome, but its pathophysiology is not fully understood. Methods: We applied 3D magnetic resonance spectroscopic imaging (MRSI), covering multiple cortical and subcortical brain regions, to investigate the association between neuro-metabolite (e.g. combined glutamate and glutamine, Glx; myo-inositol, mIno; and combined (total) N-acetylaspartate and N-acetylaspartylglutamate, tNAA) levels and multidimensional clinical/behavioural variables (e.g. pain catastrophizing, clinical pain severity and evoked pain sensitivity) in women with fibromyalgia (N = 87). Results: Pain catastrophizing scores were positively correlated with Glx and tNAA levels in insular cortex, and negatively correlated with mIno levels in posterior cingulate cortex (PCC). Clinical pain severity was positively correlated with Glx levels in insula and PCC, and with tNAA levels in anterior midcingulate cortex (aMCC), but negatively correlated with mIno levels in aMCC and thalamus. Evoked pain sensitivity was negatively correlated with levels of tNAA in insular cortex, MCC, PCC and thalamus. Conclusions: These findings support single voxel placement targeting nociceptive processing areas in prior 1 H-MRS studies, but also highlight other areas not as commonly targeted, such as PCC, as important for chronic pain pathophysiology. Identifying target brain regions linked to multidimensional symptoms of fibromyalgia (e.g. negative cognitive/affective response to pain, clinical pain, evoked pain sensitivity) may aid the development of neuromodulatory and individualized therapies.Furthermore, efficient multi-region sampling with 3D MRSI could reduce the burden of lengthy scan time for clinical research applications of molecular brain-based mechanisms supporting multidimensional aspects of fibromyalgia. Significance: This large N study linked brain metabolites and pain features in fibromyalgia patients, with a better spatial resolution and brain coverage, to understand a molecular mechanism underlying pain catastrophizing and other aspects of pain

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Regulation of N‐acetylaspartate and N‐acetylaspartylglutamate biosynthesis by protein kinase activators

Cited by 63 publications

References 35 publications

Molecular Identification of N-Acetylaspartylglutamate Synthase and β-Citrylglutamate Synthase

Molecular Identification of N-Acetylaspartylglutamate Synthase and β-Citrylglutamate Synthase

N-Acetylaspartate in the CNS: From neurodiagnostics to neurobiology

3D magnetic resonance spectroscopic imaging reveals links between brain metabolites and multidimensional pain features in fibromyalgia

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