Dataset Information

D-Serine Metabolism and Its Importance in Development of Dictyostelium discoideum.

ABSTRACT: In mammals, D-Ser is synthesized by serine racemase (SR) and degraded by D-amino acid oxidase (DAO). D-Ser acts as an endogenous ligand for N-methyl-D-aspartate (NMDA)- and ?2 glutamate receptors, and is involved in brain functions such as learning and memory. Although SR homologs are highly conserved in eukaryotes, little is known about the significance of D-Ser in non-mammals. In contrast to mammals, the slime mold Dictyostelium discoideum genome encodes SR, DAO, and additionally D-Ser specific degradation enzyme D-Ser dehydratase (DSD), but not NMDA- and ?2 glutamate receptors. Here, we studied the significances of D-Ser and DSD in D. discoideum. Enzymatic assays demonstrated that DSD is 460- and 1,700-fold more active than DAO and SR, respectively, in degrading D-Ser. Moreover, in dsd-null cells D-Ser degradation activity is completely abolished. In fact, while in wild-type D. discoideum intracellular D-Ser levels were considerably low, dsd-null cells accumulated D-Ser. These results indicated that DSD but not DAO is the primary enzyme responsible for D-Ser decomposition in D. discoideum. We found that dsd-null cells exhibit delay in development and arrest at the early culmination stage. The efficiency of spore formation was considerably reduced in the mutant cells. These phenotypes were further pronounced by exogenous D-Ser but rescued by plasmid-borne expression of dsd. qRT-PCR analysis demonstrated that mRNA expression of key genes in the cAMP signaling relay is perturbed in the dsd knockout. Our data indicate novel roles for D-Ser and/or DSD in the regulation of cAMP signaling in the development processes of D. discoideum.

SUBMITTER: Ito T

PROVIDER: S-EPMC5928759 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Publications

D-Serine Metabolism and Its Importance in Development of Dictyostelium discoideum.

Ito Tomokazu T Hamauchi Natsuki N Hagi Taisuke T Morohashi Naoya N Hemmi Hisashi H Sato Yukie G YG Saito Tamao T Yoshimura Tohru T

Frontiers in microbiology 20180424

In mammals, D-Ser is synthesized by serine racemase (SR) and degraded by D-amino acid oxidase (DAO). D-Ser acts as an endogenous ligand for N-methyl-D-aspartate (NMDA)- and δ2 glutamate receptors, and is involved in brain functions such as learning and memory. Although SR homologs are highly conserved in eukaryotes, little is known about the significance of D-Ser in non-mammals. In contrast to mammals, the slime mold Dictyostelium discoideum genome encodes SR, DAO, and additionally ...[more]

PMID: 29740415

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Project description:The social amoeba Dictyostelium discoideum was instrumental in the discovery and early characterization of inositol pyrophosphates, a class of molecules possessing highly-energetic pyrophosphate bonds. Inositol pyrophosphates regulate diverse biological processes and are attracting attention due to their ability to control energy metabolism and insulin signalling. However, inositol pyrophosphate research has been hampered by the lack of simple experimental procedures to study them. The recent development of polyacrylamide gel electrophoresis (PAGE) and simple staining to resolve and detect inositol pyrophosphate species has opened new investigative possibilities. This technology is now commonly applied to study in vitro enzymatic reactions. Here we employ PAGE technology to characterize the D. discoideum inositol pyrophosphate metabolism. Surprisingly, only three major bands are detectable after resolving acidic extract on PAGE. We have demonstrated that these three bands correspond to inositol hexakisphosphate (IP₆ or Phytic acid) and its derivative inositol pyrophosphates, IP₇ and IP₈. Biochemical analyses and genetic evidence were used to establish the genuine inositol phosphate nature of these bands. We also identified IP₉ in D. discoideum cells, a molecule so far detected only from in vitro biochemical reactions. Furthermore, we discovered that this amoeba possesses three different inositol pentakisphosphates (IP₅) isomers, which are largely metabolised to inositol pyrophosphates. Comparison of PAGE with traditional Sax-HPLC revealed an underestimation of the cellular abundance of inositol pyrophosphates by traditional methods. In fact our study revealed much higher levels of inositol pyrophosphates in D. discoideum in the vegetative state than previously detected. A three-fold increase in IP₈ was observed during development of D. discoideum a value lower that previously reported. Analysis of inositol pyrophosphate metabolism using ip6k null amoeba revealed the absence of developmentally-induced synthesis of inositol pyrophosphates, suggesting that the alternative class of enzyme responsible for pyrophosphate synthesis, PP-IP₅K, doesn't' play a major role in the IP₈ developmental increase.

Dataset Information

D-Serine Metabolism and Its Importance in Development of Dictyostelium discoideum.

Publications

D-Serine Metabolism and Its Importance in Development of <i>Dictyostelium discoideum</i>.

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