Brousseau D et al. (1998) Midwest Worm Meeting "A Remarkably Large and Diverse Group of Insulin Superfamily Genes in C. elegans"

Heller J, Homburger S, Quinn S, Brousseau D, Platt D, Costa M, Ferguson KC, Devadhar S, Buchman A, Reddy B, Doberstein S

[Midwest Worm Meeting, 1998]

We are using combined genetic and genomic analyses to identify new C. elegans genes involved in insulin receptor signaling. As a starting point, we have characterized a group of insulin-related genes that is considerably larger and more diverse than that recognized in other organisms. The insulin superfamily genes analyzed to date are expressed primarily in subsets of neurons, where they might function as neuromodulators or hormones. Kimura et al., 1997 (Science 277: 942) have shown that the daf-2 gene, which is required to prevent dauer formation, encodes an insulin receptor homolog. We are in the process of generating loss- and gain-of-function phenotypes for the insulin homologs, and determining whether any of these genes may encode ligands for the DAF-2 receptor. In addition, we have used RNA-mediated interference to identify new genes acting downstream of the DAF-2 receptor in the dauer formation pathway. Vertebrate orthologs of these genes might represent novel drug targets for the treatment of type II diabetes.

Brousseau D et al. (1998) West Coast Worm Meeting "AN INSULIN-RELATED GENE FAMILY OF UNPRECEDENTED SIZE AND DIVERSITY IN C. ELEGANS"

Costa M, Buchman A, Homburger S, Devadhar S, Platt D, Heller J, Brousseau D, Quinn S, Doberstein S, Reddy B, Ferguson KC

[West Coast Worm Meeting, 1998]

We are using combined genetic and genomic analyses to identify new C. elegans genes involved in insulin receptor signaling. As a starting point, we have systematically searched the C. elegans genome for genes encoding members of the insulin superfamily. We identified, cloned, and confirmed the sequence of thirty-one ins (insulin superfamily) genes, a family that is considerably larger and more diverse than anticipated. Sequence analysis and structural modeling indicates that some of these proteins have structural variations relative to previously recognized superfamily members. These variations include an additional predicted disulfide bond between A and B chains, absence of the A chain disulfide bond, multiple A and B chains, and absence of a cleavable C peptide. Duret et al., 1998 (Genome Research 8: 248) have independently identified 10 of these genes and noted similar structural deviations. The ins genes analyzed to date are expressed primarily in subsets of chemosensory and other neurons, where they might function as neuromodulators or hormones. Kimura et al., 1997 (Science 277: 942) have shown that the daf-2 gene, which is required to prevent dauer formation, encodes an insulin receptor homolog. We are in the process of generating loss- and gain-of-function phenotypes for the insulin homologs, and determining whether any of these genes may encode ligands for the DAF-2 receptor. In addition, we have used RNA-mediated interference to confirm new candidate genes in the dauer formation pathway. This approach has revealed the presence of two protein kinase B (PKB)/Akt homologs, pkb-1 and pkb-2. RNA mediated interference of either pkb-1 or pkb-2 alone has no effect, while simultaneous inactivation of both genes causes a non-conditional dauer constitutive (Daf-c) phenotype, similar to the daf-2 mutant phenotype. Epistasis analysis places pkb-1 and pkb-2 upstream of the DAF-16 transcription factor in the dauer formation pathway. This analysis further extends our knowledge of the conservation of the insulin receptor signaling pathway between vertebrates and C. elegans.

Brousseau D et al. (1998) East Coast Worm Meeting "A Remarkably Large and Diverse Group of Insulin Superfamily Genes in C. elegans"

Devadhar S, Homburger S, Heller J, Buchman A, Platt D, Costa M, Quinn S, Reddy B, Ferguson KC, Doberstein S, Brousseau D

[East Coast Worm Meeting, 1998]

We are using combined genetic and genomic analyses to identify new C. elegans genes involved in insulin receptor signaling. As a starting point, we have characterized a group of insulin-related genes that is considerably larger and more diverse than that recognized in other organisms. The insulin superfamily genes analyzed to date are expressed primarily in subsets of neurons, where they might function as neuromodulators or hormones. Kimura et al., 1997 (Science 277: 942) have shown that the daf-2 gene, which is required to prevent dauer formation, encodes an insulin receptor homolog. We are in the process of generating loss- and gain-of-function phenotypes for the insulin homologs, and determining whether any of these genes may encode ligands for the DAF-2 receptor. In addition, we have used RNA-mediated interference to identify new genes acting downstream of the DAF-2 receptor in the dauer formation pathway. Vertebrate orthologs of these genes might represent novel drug targets for the treatment of type II diabetes.

Sakoguchi H et al. (2016) Biosci Biotechnol Biochem "Screening of biologically active monosaccharides: growth inhibitory effects of d-allose, d-talose, and l-idose against the nematode Caenorhabditis elegans."

Izumori K, Yoshihara A, Sakoguchi H, Sato M

[Biosci Biotechnol Biochem, 2016]

We compared the growth inhibitory effects of all aldohexose stereoisomers against the model animal Caenorhabditis elegans. Among the tested compounds, the rare sugars d-allose (d-All), d-talose (d-Tal), and l-idose (l-Ido) showed considerable growth inhibition under both monoxenic and axenic culture conditions. 6-Deoxy-d-All had no effect on growth, which suggests that C6-phosphorylation by hexokinase is essential for inhibition by d-All.

Sakoguchi H et al. (2016) Bioorg Med Chem Lett "Growth inhibitory effect of d-arabinose against the nematode Caenorhabditis elegans: Discovery of a novel bioactive monosaccharide."

Shintani T, Izumori K, Sato M, Sakoguchi H, Okuma K, Yoshihara A

[Bioorg Med Chem Lett, 2016]

Biological activities of unusual monosaccharides (rare sugars) have largely remained unstudied until recently. We compared the growth inhibitory effects of aldohexose stereoisomers against the animal model Caenorhabditis elegans cultured in monoxenic conditions with Escherichia coli as food. Among these stereoisomers, the rare sugar d-arabinose (d-Ara) showed particularly strong growth inhibition. The IC50 value for d-Ara was estimated to be 7.5mM, which surpassed that of the potent glycolytic inhibitor 2-deoxy-d-glucose (19.5mM) used as a positive control. The inhibitory effect of d-Ara was also observed in animals cultured in axenic conditions using a chemically defined medium; this excluded the possible influence of E. coli. To our knowledge, this is the first report of biological activity of d-Ara. The d-Ara-induced inhibition was recovered by adding either d-ribose or d-fructose, but not d-glucose. These findings suggest that the inhibition could be induced by multiple mechanisms, for example, disturbance of d-ribose and d-fructose metabolism.

Yoshihara A et al. (2019) Bioorg Med Chem Lett "Growth inhibition by 1-deoxy-d-allulose, a novel bioactive deoxy sugar, screened using Caenorhabditis elegans assay."

Sakoguchi H, Fleet GWJ, Izumori K, Shintani T, Sato M, Yoshihara A

[Bioorg Med Chem Lett, 2019]

The biological activities of deoxy sugars (deoxy monosaccharides) have remained largely unstudied until recently. We compared the growth inhibition by all 1-deoxyketohexoses using the animal model Caenorhabditis elegans. Among the eight stereoisomers, 1-deoxy-d-allulose (1d-d-Alu) showed particularly strong growth inhibition. The 50% inhibition of growth (GI₅₀) concentration by 1d-d-Alu was estimated to be 5.4mM, which is approximately 10 times lower than that of d-allulose (52.7mM), and even lower than that of the potent glycolytic inhibitor, 2-deoxy-d-glucose (19.5mM), implying that 1d-d-Alu has a strong growth inhibition. In contrast, 5-deoxy- and 6-deoxy-d-allulose showed no growth inhibition of C. elegans. The inhibition by 1d-d-Alu was alleviated by the addition of d-ribose or d-fructose. Our findings suggest that 1d-d-Alu-mediated growth inhibition could be induced by the imbalance in d-ribose metabolism. To our knowledge, this is the first report of biological activity of 1d-d-Alu which may be considered as an antimetabolite drug candidate.

Katane M et al. (2020) Biochim Biophys Acta Proteins Proteom "Biochemical characterization of d-aspartate oxidase from Caenorhabditis elegans: Its potential use in the determination of free D-glutamate in biological samples."

Katane M, Sekine M, Nakayama K, Homma H, Kuwabara H, Saitoh Y, Miyamoto T

[Biochim Biophys Acta Proteins Proteom, 2020]

d-Aspartate oxidase (DDO) is a flavin adenine dinucleotide (FAD)-containing flavoprotein that stereospecifically acts on acidic D-amino acids (i.e., free d-aspartate and D-glutamate). Mammalian DDO, which exhibits higher activity toward d-aspartate than D-glutamate, is presumed to regulate levels of d-aspartate in the body and is not thought to degrade D-glutamate in vivo. By contrast, three DDO isoforms are present in the nematode Caenorhabditis elegans, DDO-1, DDO-2, and DDO-3, all of which exhibit substantial activity toward D-glutamate as well as d-aspartate. In this study, we optimized the Escherichia coli culture conditions for production of recombinant C. elegans DDO-1, purified the protein, and showed that it is a flavoprotein with a noncovalently but tightly attached FAD. Furthermore, C. elegans DDO-1, but not mammalian (rat) DDO, efficiently and selectively degraded D-glutamate in addition to d-aspartate, even in the presence of various other amino acids. Thus, C. elegans DDO-1 might be a useful tool for determining these acidic D-amino acids in biological samples.

Shintani T et al. (2019) J Appl Glycosci (1999) "D-Allose, a Stereoisomer of D-Glucose, Extends the Lifespan of Caenorhabditis elegans via Sirtuin and Insulin Signaling."

Izumori K, Sakoguchi H, Yoshihara A, Shintani T, Sato M

[J Appl Glycosci (1999), 2019]

D-Allose (D-All), C-3 epimer of D-glucose, is a rare sugar known to suppress reactive oxygen species generation and prevent hypertension. We previously reported that D-allulose, a structural isomer of D-All, prolongs the lifespan of the nematode Caenorhabditis elegans. Thus, D-All was predicted to affect longevity. In this study, we provide the first empirical evidence that D-All extends the lifespan of C. elegans. Lifespan assays revealed that a lifespan extension was induced by 28 mM D-All. In particular, a lifespan extension of 23.8 % was achieved (p< 0.0001). We further revealed that the effects of D-All on lifespan were dependent on the insulin gene daf-16 and the longevity gene sir-2.1, indicating a distinct mechanism from those of other hexoses, such as D-allulose, with previously reported antiaging effects.

Sato M et al. (2008) J Nat Med "Potential anthelmintic: D-psicose inhibits motility, growth and reproductive maturity of L1 larvae of Caenorhabditis elegans."

Izumori K, Yamasaki T, Kurose H, Sato M

[J Nat Med, 2008]

No anthelmintic sugars have yet been identified. Eight ketohexose stereoisomers (D- and L-forms of psicose, fructose, tagatose and sorbose), along with D-galactose and D-glucose, were examined for potency against L1 stage Caenorhabditis elegans fed Escherichia coli. Of the sugars, D-psicose specifically inhibited the motility, growth and reproductive maturity of the L1 stage. D-Psicose probably interferes with the nematode nutrition. The present results suggest that D-psicose, one of the rare sugars, is a potential anthelmintic.

Yasuaki Saitoh et al. (2010) East Asia Worm Meeting "Study on physiological functions of D-amino acid degradative enzymes in nematode Caenorhabditis elegans"

Yousuke Seida, Kazuhiro Maeda, Tomonori Kawata, Masumi Katane, Hiroyuki Kobuna, Takao Inoue, Yasuaki Saitoh, Hiroyuki Arai, Yasuhito Nakagawa, Masae Sekine, Taro Sakamoto, Hiroshi Homma, Takemitsu Furuchi

[East Asia Worm Meeting, 2010]

Among free D-amino acids existing in living organisms, D-serine (D-Ser) and D-aspartate (D-Asp) are the most actively studied. D-Ser has been proposed as a neuromodulator that regulates L-glutamate-mediated activation of the N-methyl-D-Asp (NMDA) receptor by acting as a co-agonist. On the other hand, several lines of evidence suggest that D-Asp plays important roles in regulating developmental processes, hormone secretion and steroidogenesis. D-Amino acid oxidase (DAO) and D-Asp oxidase (DDO) are known as stereospecific degradative enzymes that catalyze the oxidative deamination of D-amino acids. DAO displays broad substrate specificity and acts on several neutral and basic D-amino acids, while DDO is highly specific for acidic D-amino acids. DAO and DDO are presumed to regulate endogenous D-Ser and D-Asp levels, respectively, as well as mediate the elimination of accumulated exogenous D-amino acids in various organs. Previously, we demonstrated that nematode Caenorhabditis elegans, a multicellular model animal has at least one active DAO gene and three active DDO genes, while it had been thought that most organisms bear only one copy of each DAO and DDO gene. In addition, our previous study revealed that the spatiotemporal distributions of these enzymes in the body of C. elegans are different from one another. In this study, to elucidate the physiological roles of the C. elegans DAO and DDOs, we characterized several phenotypes of four C. elegans mutants in which each gene is partially deleted and inactivated. We also determined free D-amino acid contents in several worm samples using high-performance liquid chromatography (HPLC) techniques. We will report the phenotypes of the C. elegans mutants in comparison with those of wild-type C. elegans, as well as alterations in D-amino acid levels within the body.