title: The protein partners of GTP cyclohydrolase I in rat organs.
abstract: OBJECTIVE
  GTP cyclohydrolase I (GCH1) is the rate-limiting enzyme for tetrahydrobiopterin biosynthesis and has been shown to be a promising therapeutic target in ischemic heart disease, hypertension, atherosclerosis and diabetes. The endogenous GCH1-interacting partners have not been identified. Here, we determined endogenous GCH1-interacting proteins in rat.
  
  
  RESULTS
  A pulldown and proteomics approach were used to identify GCH1 interacting proteins in rat liver, brain, heart and kidney. We demonstrated that GCH1 interacts with at least 17 proteins including GTP cyclohydrolase I feedback regulatory protein (GFRP) in rat liver by affinity purification followed by proteomics and validated six protein partners in liver, brain, heart and kidney by immunoblotting. GCH1 interacts with GFRP and very long-chain specific acyl-CoA dehydrogenase in the liver, tubulin beta-2A chain in the liver and brain, DnaJ homolog subfamily A member 1 and fatty aldehyde dehydrogenase in the liver, heart and kidney and eukaryotic translation initiation factor 3 subunit I (EIF3I) in all organs tested. Furthermore, GCH1 associates with mitochondrial proteins and GCH1 itself locates in mitochondria.
  
  
  CONCLUSIONS
  GCH1 interacts with proteins in an organ dependant manner and EIF3I might be a general regulator of GCH1. Our finding indicates GCH1 might have broader functions beyond tetrahydrobiopterin biosynthesis.
authors.affiliation: Department of Surgery, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America. dujianhai@gmail.com
authors.forename: Jianhai
authors.initials: J
authors.lastname: Du
authors.forename: Ru-Jeng
authors.initials: RJ
authors.lastname: Teng
authors.forename: Matt
authors.initials: M
authors.lastname: Lawrence
authors.forename: Tongju
authors.initials: T
authors.lastname: Guan
authors.forename: Hao
authors.initials: H
authors.lastname: Xu
authors.forename: Ying
authors.initials: Y
authors.lastname: Ge
authors.forename: Yang
authors.initials: Y
authors.lastname: Shi
mesh_terms: D044942:Acyl-CoA Dehydrogenase, Long-Chain / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D039621:Eukaryotic Initiation Factor-3 / Q000378:metabolism; D006136:GTP Cyclohydrolase / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008099:Liver / Q000378:metabolism; D008297:Male; D008928:Mitochondria / Q000378:metabolism; D046912:Multiprotein Complexes / Q000302:isolation & purification; D011485:Protein Binding; D025941:Protein Interaction Mapping; D021381:Protein Transport; D011506:Proteins / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results; D050697:Retinal Dehydrogenase / Q000378:metabolism
chemical_list: D039621:Eukaryotic Initiation Factor-3; C491065:Gchfr protein, rat; D047908:Intracellular Signaling Peptides and Proteins; D046912:Multiprotein Complexes; D011506:Proteins; D050697:Retinal Dehydrogenase; D044942:Acyl-CoA Dehydrogenase, Long-Chain; D006136:GTP Cyclohydrolase