title: Isolation of novel animal cell lines defective in glycerolipid biosynthesis reveals mutations in glucose-6-phosphate isomerase.
abstract: Glycerolipids are structural components for membranes and serve in energy storage. We describe here the use of a photodynamic selection technique to generate a population of Chinese hamster ovary cells that display a global deficiency in glycerolipid biosynthesis. One isolate from this population, GroD1, displayed a profound reduction in the synthesis of phosphatidylcholine, phosphatidylethanolamine, and triglycerides but presented high levels of phosphatidic acid and normal levels of phosphatidylinositol synthesis. This was accompanied by a reduction in phosphatidate phosphatase 1 (PAP1) activity. Expression cloning and sequencing of the cDNA obtained from GroD1 revealed a point mutation, Gly-189 --> Glu, in glucose-6-phosphate isomerase (GPI), a glycolytic enzyme involved in an inherited disorder that results in anemia and neuromuscular symptoms in humans. GPI activity was reduced by 87% in GroD1. No significant differences were found in DNA synthesis, protein synthesis, and ATP levels, whereas glycerol 3-phosphate levels were increased in the mutant. Expression of wild-type hamster GPI restored GPI activity, glycerolipid biosynthesis, and PAP1 activity in GroD1. Two additional, independently isolated GPI-deficient mutants displayed similar phenotypes with respect to PAP1 activity and glycerolipid biosynthesis. These findings uncover a novel relationship between GPI, involved in carbohydrate metabolism, and PAP1, a lipogenic enzyme. These results may also help to explain neuromuscular symptoms associated with inherited GPI deficiency.
authors.affiliation: Department of Physiology and Biophysics, Boston University School of Medicine, Massachusetts 02118, USA.
authors.forename: Jorge F
authors.initials: JF
authors.lastname: Haller
authors.forename: Conor
authors.initials: C
authors.lastname: Smith
authors.forename: Dailan
authors.initials: D
authors.lastname: Liu
authors.forename: Hongying
authors.initials: H
authors.lastname: Zheng
authors.forename: Keith
authors.initials: K
authors.lastname: Tornheim
authors.forename: Gil-Soo
authors.initials: GS
authors.lastname: Han
authors.forename: George M
authors.initials: GM
authors.lastname: Carman
authors.forename: Raphael A
authors.initials: RA
authors.lastname: Zoeller
mesh_terms: D000740:Anemia / Q000201:enzymology / Q000235:genetics; D000818:Animals; D000951:Antigens, Neoplasm / Q000235:genetics / Q000378:metabolism; D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D005956:Glucose-6-Phosphate Isomerase / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D037181:Lectins, C-Type / Q000235:genetics / Q000378:metabolism; D008661:Metabolism, Inborn Errors / Q000201:enzymology / Q000235:genetics; D009468:Neuromuscular Diseases / Q000201:enzymology / Q000235:genetics; D000073718:Pancreatitis-Associated Proteins; D010743:Phospholipids / Q000096:biosynthesis* / Q000235:genetics; D017354:Point Mutation; D014280:Triglycerides / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; D037181:Lectins, C-Type; D000073718:Pancreatitis-Associated Proteins; D010743:Phospholipids; C000612141:REG3A protein, human; D014280:Triglycerides; D005956:Glucose-6-Phosphate Isomerase