title: Propionyl-CoA and adenosylcobalamin metabolism in Caenorhabditis elegans: evidence for a role of methylmalonyl-CoA epimerase in intermediary metabolism.
abstract: We have utilized Caenorhabditis elegans to study human methylmalonic acidemia. Using bioinformatics, a full complement of mammalian homologues for the conversion of propionyl-CoA to succinyl-CoA in the genome of C. elegans, including propionyl-CoA carboxylase subunits A and B (pcca-1, pccb-1), methylmalonic acidemia cobalamin A complementation group (mmaa-1), co(I)balamin adenosyltransferase (mmab-1), MMACHC (cblc-1), methylmalonyl-CoA epimerase (mce-1) and methylmalonyl-CoA mutase (mmcm-1) were identified. To verify predictions that the entire intracellular adenosylcobalamin metabolic pathway existed and was functional, the kinetic properties of the C. elegans mmcm-1 were examined. RNA interference against mmcm-1, mmab-1, mmaa-1 in the presence of propionic acid revealed a chemical phenotype of increased methylmalonic acid; deletion mutants of mmcm-1, mmab-1 and mce-1 displayed reduced 1-[(14)C]-propionate incorporation into macromolecules. The mutants produced increased amounts of methylmalonic acid in the culture medium, proving that a functional block in the pathway caused metabolite accumulation. Lentiviral delivery of the C. elegans mmcm-1 into fibroblasts derived from a patient with mut(o) class methylmalonic acidemia could partially restore propionate flux. The C. elegans mce-1 deletion mutant demonstrates for the first time that a lesion at the epimerase step of methylmalonyl-CoA metabolism can functionally impair flux through the methylmalonyl-CoA mutase pathway and suggests that malfunction of MCEE may cause methylmalonic acidemia in humans. The C. elegans system we describe represents the first lower metazoan model organism of mammalian propionate spectrum disorders and demonstrates that mass spectrometry can be employed to study a small molecule chemical phenotype in C. elegans RNAi and deletion mutants.
authors.affiliation: Genetic Disease Research Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Randy J
authors.initials: RJ
authors.lastname: Chandler
authors.forename: Vijay
authors.initials: V
authors.lastname: Aswani
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Tsai
authors.forename: Marni
authors.initials: M
authors.lastname: Falk
authors.forename: Natasha
authors.initials: N
authors.lastname: Wehrli
authors.forename: Sally
authors.initials: S
authors.lastname: Stabler
authors.forename: Robert
authors.initials: R
authors.lastname: Allen
authors.forename: Margaret
authors.initials: M
authors.lastname: Sedensky
authors.forename: Haig H
authors.initials: HH
authors.lastname: Kazazian
authors.forename: Charles P
authors.initials: CP
authors.lastname: Venditti
mesh_terms: D000138:Acidosis / Q000201:enzymology* / Q000235:genetics; D000214:Acyl Coenzyme A / Q000378:metabolism*; D019883:Alkyl and Aryl Transferases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology; D000818:Animals; D017173:Caenorhabditis elegans / Q000201:enzymology* / Q000235:genetics; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D003038:Cobamides / Q000378:metabolism*; D019295:Computational Biology; D004195:Disease Models, Animal; D005347:Fibroblasts / Q000201:enzymology; D005816:Genetic Complementation Test; D006801:Humans; D008764:Methylmalonic Acid / Q000097:blood; D008765:Methylmalonyl-CoA Mutase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology; D034622:RNA Interference; D019998:Racemases and Epimerases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D014162:Transfection
chemical_list: D000214:Acyl Coenzyme A; D029742:Caenorhabditis elegans Proteins; D003038:Cobamides; C009061:propionyl-coenzyme A; D008764:Methylmalonic Acid; D019883:Alkyl and Aryl Transferases; C019920:cob(I)alamin adenosyltransferase; D019998:Racemases and Epimerases; C021581:methylmalonyl-coenzyme A racemase; D008765:Methylmalonyl-CoA Mutase; C000913:cobamamide