title: Reassessing the Potential Activities of Plant CGI-58 Protein.
abstract: Comparative Gene Identification-58 (CGI-58) is a widespread protein found in animals and plants. This protein has been shown to participate in lipolysis in mice and humans by activating Adipose triglyceride lipase (ATGL), the initial enzyme responsible for the triacylglycerol (TAG) catabolism cascade. Human mutation of CGI-58 is the cause of Chanarin-Dorfman syndrome, an orphan disease characterized by a systemic accumulation of TAG which engenders tissue disorders. The CGI-58 protein has also been shown to participate in neutral lipid metabolism in plants and, in this case, a mutation again provokes TAG accumulation. Although its roles as an ATGL coactivator and in lipid metabolism are quite clear, the catalytic activity of CGI-58 is still in question. The acyltransferase activities of CGI-58 have been speculated about, reported or even dismissed and experimental evidence that CGI-58 expressed in E. coli possesses an unambiguous catalytic activity is still lacking. To address this problem, we developed a new set of plasmids and site-directed mutants to elucidate the in vivo effects of CGI-58 expression on lipid metabolism in E. coli. By analyzing the lipid composition in selected E. coli strains expressing CGI-58 proteins, and by reinvestigating enzymatic tests with adequate controls, we show here that recombinant plant CGI-58 has none of the proposed activities previously described. Recombinant plant and mouse CGI-58 both lack acyltransferase activity towards either lysophosphatidylglycerol or lysophosphatidic acid to form phosphatidylglycerol or phosphatidic acid and recombinant plant CGI-58 does not catalyze TAG or phospholipid hydrolysis. However, expression of recombinant plant CGI-58, but not mouse CGI-58, led to a decrease in phosphatidylglycerol in all strains of E. coli tested, and a mutation of the putative catalytic residues restored a wild-type phenotype. The potential activities of plant CGI-58 are subsequently discussed.
authors.affiliation: Institut de Chimie et de Biochimie Moléculaires et Supramoléculaires UMR 5246 CNRS, Organisation et Dynamique des Membranes Biologiques, Université Lyon 1, Villeurbanne, France.
authors.forename: Abdallah
authors.initials: A
authors.lastname: Khatib
authors.affiliation: Institut de Chimie et de Biochimie Moléculaires et Supramoléculaires UMR 5246 CNRS, Organisation et Dynamique des Membranes Biologiques, Université Lyon 1, Villeurbanne, France.
authors.forename: Yani
authors.initials: Y
authors.lastname: Arhab
authors.affiliation: Institut de Chimie et de Biochimie Moléculaires et Supramoléculaires UMR 5246 CNRS, Organisation et Dynamique des Membranes Biologiques, Université Lyon 1, Villeurbanne, France.
authors.forename: Assia
authors.initials: A
authors.lastname: Bentebibel
authors.affiliation: Institut de Chimie et de Biochimie Moléculaires et Supramoléculaires UMR 5246 CNRS, Organisation et Dynamique des Membranes Biologiques, Université Lyon 1, Villeurbanne, France.
authors.forename: Abdelkarim
authors.initials: A
authors.lastname: Abousalham
authors.affiliation: Institut de Chimie et de Biochimie Moléculaires et Supramoléculaires UMR 5246 CNRS, Organisation et Dynamique des Membranes Biologiques, Université Lyon 1, Villeurbanne, France.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Noiriel
mesh_terms: D000217:Acyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D017360:Arabidopsis / Q000201:enzymology; D055162:Biocatalysis; D003001:Cloning, Molecular; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000378:metabolism; D006868:Hydrolysis; D050356:Lipid Metabolism; D051379:Mice; D008969:Molecular Sequence Data; D010641:Phenotype; D010715:Phosphatidylglycerols / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000302:isolation & purification; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014280:Triglycerides / Q000378:metabolism
chemical_list: D010715:Phosphatidylglycerols; D010940:Plant Proteins; D011994:Recombinant Proteins; D014280:Triglycerides; D000217:Acyltransferases; C018764:2-acylglycerophosphate acyltransferase