An overview of combined D-2-and L-2-hydroxyglutaric aciduria: functional analysis of CIC variants
JOURNAL OF INHERITED METABOLIC DISEASE
Authors: Pop, Ana; Williams, Monique; Struys, Eduard A.; Monne, Magnus; Jansen, Erwin E. W.; De Grassi, Anna; Kanhai, Warsha A.; Scarcia, Pasquale; Ojed, Matilde R. Fernandez; Porcelli, Vito; van Dooren, Silvy J. M.; Lennertz, Pascal; Nota, Benjamin; Abdenur, Jose E.; Coman, David; Das, Anibh Martin; El-Gharbawy, Areeg; Nuoffer, Jean-Marc; Polic, Branka; Santer, Rene; Weinhold, Natalie; Zuccarelli, Britton; Palmieri, Ferdinando; Palmieri, Luigi; Salomons, Gajja S.
Abstract
Combined D-2- and L-2-hydroxyglutaric aciduria (D/L-2-HGA) is a devastating neurometabolic disorder, usually lethal in the first years of life. Autosomal recessive mutations in the SLC25A1 gene, which encodes the mitochondrial citrate carrier (CIC), were previously detected in patients affected with combined D/L-2-HGA. We showed that transfection of deficient fibroblasts with wild-type SLC25A1 restored citrate efflux and decreased intracellular 2-hydroxyglutarate levels, confirming that deficient CIC is the cause of D/L-2-HGA. We developed and implemented a functional assay and applied it to all 17 missense variants detected in a total of 26 CIC-deficient patients, including eight novel cases, showing reduced activities of varying degrees. In addition, we analyzed the importance of residues affected by these missense variants using our existing scoring system. This allowed not only a clinical and biochemical overview of the D/L-2-HGA patients but also phenotype-genotype correlation studies.
The Aspergillus nidulans acuL gene encodes a mitochondrial carrier required for the utilization of carbon sources that are metabolized via the TCA cycle
FUNGAL GENETICS AND BIOLOGY
Authors: Flipphi, Michel; Oestreicher, Nathalie; Nicolas, Valerie; Guitton, Audrey; Velot, Christian
Abstract
In Aspergillus nidulans, the utilization of acetate as sole carbon source requires several genes (acu). Most of them are also required for the utilization of fatty acids. This is the case for acuD and acuE, which encode the two glyoxylate cycle-specific enzymes, isocitrate lyase and malate synthase, respectively, but also for acuL that we have identified as AN7287, and characterized in this study. Deletion of acuL resulted in the same phenotype as the original acuL217 mutant. acuL encodes a 322-amino acid protein which displays all the structural features of a mitochondrial membrane carrier, and shares 60% identity with the Saccharomyces cerevisiae succinate/fumarate mitochondrial antiporter Sfc1p (also named Acr1p). Consistently, the AcuL protein was shown to localize in mitochondria, and partial cross-complementation was observed between the S. cerevisiae and A. nidulans homologues. Extensive phenotypic characterization suggested that the acuL gene is involved in the utilization of carbon sources that are catabolized via the TCA cycle, and therefore require gluconeogenesis. In addition, acuL proves to be co-regulated with acuD and acuE. Overall, our data suggest that AcuL could link the glyoxylate cycle to gluconeogenesis by exchanging cytoplasmic succinate for mitochondrial fumarate. (C) 2014 Elsevier Inc. All rights reserved.