N-acetylaspartylglutamate: an endogenous peptide with high affinity for a brain "glutamate" receptor.

Zaczek, Robert; Koller, Kerry J.; Cotter, Robert J.; Heller, David; Coyle, Joseph T.

doi:10.1073/pnas.80.4.1116

Cited by 92 publications

(44 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It may be of interest to investigate the possibility of the occurrence of NAGGN in higher organisms, considering the rich variety of peptides that have already been found in animals. Presently, the dipeptide with the closest structural relation to NAGGN is the mammalian neurotransmitter N-acetylaspartylglutamate (7,24). It is perhaps noteworthy that other major osmotically active species (K+ and amino acids and amino acid derivatives such as glutamate and y-aminobutyric acid) are also important in neural functioning.…”

Section: Resultsmentioning

confidence: 99%

An osmoregulated dipeptide in stressed Rhizobium meliloti

Smith

1989

J Bacteriol

110

View full text Add to dashboard Cite

One common mechanism of cellular adaptation to osmotic stress is the accumulation of organic solutes in the cytosol. We have used natural-abundance 13C nuclear magnetic resonance to identify all organic solutes that accumulate to significant levels in Rhizobium meliloti. Our studies led to the discovery of a new dipeptide, N-acetylglutaminylglutamine amide (NAGGN), which is accumulated during osmotic stress. Only rarely have peptides been shown to function in bacteria, and furthermore, this is the first example of a peptide playing a role in osmoregulation. Evidence for the biological role of NAGGN in osmotic-stress protection is presented.Osmotic stress is a problem with which all forms of life must deal. Adaption to osmotic stress, termed osmoregulation, allows cells to tolerate adverse conditions such as drought or high salinity. A common mechanism of osmoregulation is the accumulation of inorganic or organic solutes or both in the cytosol to restore turgor in plants and microbes or to control cell volume in animals (13,22). The osmotically active organic solutes (osmolytes) fall into three general classes (22): polyols (sugars, sugar alcohols, glycerol), amino acids and amino acid derivatives (glutamate, proline, betaines, y-aminobutyric acid, taurine), and urea and methylamines (trimethylamine-N-oxide). Examples of these osmolytes can be found in microbes, plants, and animals. Even in mammals, osmolytes are observed: the osmotically stressed accumulation of glycine betaine and taurine in kidney (6) and heart tissues (21), respectively, has been reported.Although osmolytes are usually identified and quantitated by chemical means, natural-abundance 13C nuclear magnetic resonance (NMR) spectroscopy has been particularly useful in the study of osmoregulation because all classes of organic compounds can be detected by this method. For example, although it was known for some time that Escherichia coli accumulates glutamate (16), Larsen et al. (12) recently found that the major osmolyte is actually trehalose. Also, the cyanobacterium Synechococcus sp., which was thought to accumulate only inorganic ions, quite unexpectedly was found to contain a high concentration of glucosylglycerol (4).Our investigation is concerned with osmoregulation in Rhizobium meliloti, the root nodule symbiont of alfalfa. This bacterial species accumulates glutamate (5) and possibly K+ (23) when osmotically stressed, but no general investigation of osmoregulation in this species has been carried out. In this report we describe the use of natural-abundance '3C NMR spectroscopy to identify all major organic osmolytes accumulated by R. meliloti. This approach led to the identification of a new osmoregulated compound, N-acetylglutaminylglutamine amide (NAGGN). Preliminary results of this work have been presented elsewhere (L. T. Smith and G. M. Smith, J. Cell Biol. 107:629, 1988 (14). The pelleted cells were extracted three times with 7% perchloric acid (total volume, 10 ml) and neutralized with KOH, and the resulting KCl04 was removed by cen...

show abstract

Section: Resultsmentioning

confidence: 99%

An osmoregulated dipeptide in stressed Rhizobium meliloti

Smith

1989

J Bacteriol

110

View full text Add to dashboard Cite

show abstract

“…NAAG activates both an ionotropic glutamate receptor (NMDA-type) (32) and the metabotropic glutamate receptor 3 and can be hydrolyzed by a cell-surface dipeptidase (glutamate carboxypeptidase II) into N-acetylaspartyl and glutamate, a neurotransmitter with broader specificity and stronger excitatory activity than NAAG (32,37). In experimental animals, high local concentrations of NAAG in the brain cause seizures (38). In vitro, ␤-NAAG also behaves as a glutamate receptor agonist (21).…”

Section: Fig 8 Identification and Quantification Of Naag In Brain Cellmentioning

confidence: 99%

Phenotypic Analysis of Seizure-prone Mice Lackingl-Isoaspartate (d-Aspartate)O-Methyltransferase

Kim

Lowenson

Clarke

et al. 1999

Journal of Biological Chemistry

View full text Add to dashboard Cite

Within proteins and peptides, both L-asparaginyl and L-aspartyl residues spontaneously degrade, generating isomerized and racemized aspartyl residues. The enzyme protein L-isoaspartate (D-aspartate) O-methyltransferase (E.C. 2.1.1.77) initiates the conversion of Lisoaspartyl and D-aspartyl residues to normal L-aspartyl residues. This "repair" reaction helps to maintain proper protein conformation by preventing the accumulation of damaged proteins containing abnormal amino acid residues. Pcmt1-/-mice manifest two key phenotypes: a fatal seizure disorder and retarded growth. In this study, we characterized both phenotypes and demonstrated that they are linked. Continuous electroencephalogram monitoring of Pcmt1-/-mice revealed that abnormal cortical activity for ϳ50% of each 24-h period, even in mice that had no visible evidence of convulsions. The fatal seizure disorder in Pcmt1-/-mice can be mitigated but not eliminated by antiepileptic drugs. Interestingly, antiepileptic therapy normalized the growth of Pcmt1-/-mice, suggesting that the growth retardation is due to seizures rather than a global disturbance in growth at the cellular level. Consistent with this concept, the growth rate of Pcmt1-/-fibroblasts was indistinguishable from that of wild-type fibroblasts.Under physiological conditions, L-asparaginyl and L-aspartyl residues in polypeptides spontaneously degrade to L-and Disoaspartyl and D-aspartyl residues with half-times ranging from a few hours to hundreds of days (1-5). These abnormal residues can affect both the structure and function of polypeptides and may underlie a portion of the aging-related loss of cellular and tissue function (6 -9). However, many organisms have evolved a strategy for reversing at least some of this damage by an enzymatic methylation reaction that is targeted directly to peptides and proteins containing the major L-isoaspartyl degradation product. The widely distributed cytosolic protein L-isoaspartate (D-aspartate) O-methyltransferase, also termed protein carboxyl methyltransferase 1 (Pcmt1), 1 can initiate the conversion of L-isoaspartyl residues to L-aspartyl residues by forming the methyl ester of the L-isoaspartyl residue (10). This ester is then converted, in a nonenzymatic reaction, to an L-succinimidyl residue. Spontaneous hydrolysis of the L-succinimidyl residue produces either an L-aspartyl or an Lisoaspartyl residue. If an L-isoaspartyl residue is produced, additional rounds of methyl esterification, succinimide formation, and hydrolysis eventually convert it to an L-aspartyl residue.

show abstract

“…These results suggest that residual potassium ions, remaining after the purification of NAAG from rat brain (16), were responsible for the excitatory actions attributed to NAAG in the piriform cortex (1). Although the mechanism remains unclear, it appears that iontophoretic application of potassium ions is sufficient to depolarize neurons in the piriform cortex and that this depolarization is inhibited by L-AP4.…”

Section: Discussionmentioning

confidence: 74%

“…The original iontophoretic studies (1) used NAAG that had been purified from rat brain (16). Thus, we purified endogenous NAAG using the cited procedure (16) but omitted the final HPLC column.…”

mentioning

confidence: 99%

See 1 more Smart Citation

An explanation for the purported excitation of piriform cortical neurons by N-acetyl-L-aspartyl-L-glutamic acid (NAAG).

Whittemore

Koerner

1989

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

The excitation of piriform cortical neurons by iontophoresis of N-acetyl-L-aspartyl-L-glutamic acid (NAAG) isolated from rat brain is frequently cited as major support for the possible neurotransmitter role of NAAG in the CNS[ffrench-Mullen, J. M. H., Koller, K., Zaczek, R., Coyle, J. T., Hori, N. & Carpenter, D. 0. (1985) Proc. Natl. Acad. Sci. USA 82, 3897-3900]. However, we have been unable to reproduce this observation using synthetic NAAG, and instead we offer an alternative explanation. In our experiments, iontophoresis of the sodium salt of synthetic NAAG did not induce single-unit spiking at sites in slices of rat piriform cortex that responded vigorously to L-glutamate. In contrast, iontophoresis of the potassium salt of synthetic NAAG or of potassium ions alone induced single unit activity. The responses to both NAAG/KCI and KCI alone were inhibited by L-2-amino-4-phosphonobutanoic acid and desensitized rapidly, as previously reported for NAAG. These results suggest that residual potassium ions, remaining after the original purification of NAAG, were responsible for the excitations attributed to NAAG.Data from electrophysiological (1-5), localization (6, 7), release (8, 9), and degradation (10) studies suggest that the endogenous dipeptide N-acetyl-L-aspartyl-L-glutamic acid (NAAG) may serve as an excitatory neurotransmitter in certain areas of the mammalian central nervous system. Of the electrophysiological evidence, the strongest support for the role of NAAG as an excitant comes from the rat piriform cortex (1,(11)(12)(13)(14), where iontophoresis of NAAG purified from rat brain was reported to evoke single neuron spiking that was inhibited by DL-2-amino-4-phosphonobutanoic acid (DL-AP4) (1). Since DL-AP4 also inhibited unit responses evoked by stimulation ofthe lateral olfactory tract (LOT), the authors suggested that NAAG may be the endogenous transmitter of the LOT. Using the sodium salt of synthetic NAAG, however, we have been unable to reproduce this observation and offer an alternative explanation. Our results suggest that in the original studies, residual potassium ions, which were present as a result of the purification of NAAG from rat brain, were responsible for the excitations attributed to NAAG. A portion of this work has appeared in abstract form (15).

show abstract

N-acetylaspartylglutamate: an endogenous peptide with high affinity for a brain "glutamate" receptor.

Cited by 92 publications

References 20 publications

An osmoregulated dipeptide in stressed Rhizobium meliloti

An osmoregulated dipeptide in stressed Rhizobium meliloti

Phenotypic Analysis of Seizure-prone Mice Lackingl-Isoaspartate (d-Aspartate)O-Methyltransferase

An explanation for the purported excitation of piriform cortical neurons by N-acetyl-L-aspartyl-L-glutamic acid (NAAG).

Contact Info

Product

Resources

About