The yeast GID complex, a novel ubiquitin ligase (E3) involved in the regulation of carbohydrate metabolism.
Glucose-dependent regulation of carbon metabolism is a subject of intensive studies. We have previously shown that the switch from gluconeogenesis to glycolysis is associated with ubiquitin-proteasome linked elimination of the key enzyme fructose-1,6-bisphosphatase. Seven glucose induced degradation deficient (Gid)-proteins found previously in a genomic screen were shown to form a complex that binds FBPase. One of the subunits, Gid2/Rmd5, contains a degenerated RING finger domain. In an in vitro assay, heterologous expression of GST-Gid2 leads to polyubiquitination of proteins. In addition, we show that a mutation in the degenerated RING domain of Gid2/Rmd5 abolishes fructose-1,6-bisphosphatase polyubiquitination and elimination in vivo. Six Gid proteins are present in gluconeogenic cells. A seventh protein, Gid4/Vid24, occurs upon glucose addition to gluconeogenic cells and is afterwards eliminated. Forcing abnormal expression of Gid4/Vid24 in gluconeogenic cells leads to fructose-1,6-bisphosphatase degradation. This suggests that Gid4/Vid24 initiates fructose-1,6-bisphosphatase polyubiquitination by the Gid complex and its subsequent elimination by the proteasome. We also show that an additional gluconeogenic enzyme, phosphoenolpyruvate carboxykinase, is subject to Gid complex-dependent degradation. Our study uncovers a new type of ubiquitin ligase complex composed of novel subunits involved in carbohydrate metabolism and identifies Gid4/Vid24 as a major regulator of this E3.
Santt
Olivier
O
Institut für Biochemie, Universität Stuttgart, 70569 Stuttgart, Germany.
Pfirrmann
Thorsten
T
Braun
Bernhard
B
Juretschke
Jeannette
J
Kimmig
Philipp
P
Scheel
Hartmut
H
Hofmann
Kay
K
Thumm
Michael
M
Wolf
Dieter H
DH
D050260:Carbohydrate Metabolism; D006597:Fructose-Bisphosphatase / Q000737:chemistry; D015971:Gene Expression Regulation, Enzymologic; D015966:Gene Expression Regulation, Fungal; D005943:Gluconeogenesis; D005947:Glucose / Q000378:metabolism; D008954:Models, Biological; D009154:Mutation; D019764:Phosphoenolpyruvate Carboxykinase (ATP) / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry* / Q000378:metabolism; D033921:Vesicular Transport Proteins
D029701:Saccharomyces cerevisiae Proteins; C111452:VID24 protein, S cerevisiae; D033921:Vesicular Transport Proteins; D044767:Ubiquitin-Protein Ligases; D006597:Fructose-Bisphosphatase; D046988:Proteasome Endopeptidase Complex; D019764:Phosphoenolpyruvate Carboxykinase (ATP); D005947:Glucose