C-terminus of heat shock protein 70-interacting protein-dependent GTP cyclohydrolase I degradation in lambs with increased pulmonary blood flow.
We showed that nitric oxide (NO) signaling is decreased in the pulmonary vasculature before the development of endothelial dysfunction in a lamb model of congenital heart disease and increased pulmonary blood flow (Shunt). The elucidation of the molecular mechanism by which this occurs was the purpose of this study. Here, we demonstrate that concentrations of the endogenous NO synthase (NOS) inhibitor, asymmetric dimethylarginine (ADMA), are elevated, whereas the NOS cofactor tetrahydrobiopterin (BH(4)) is decreased in Shunt lambs. Our previous studies demonstrated that ADMA decreases heat shock protein-90 (Hsp90) chaperone activity, whereas other studies suggest that guanosine-5'-triphosphate cyclohydrolase 1 (GCH1), the rate-limiting enzyme in the generation of BH(4), may be a client protein for Hsp90. Thus, we determined whether increases in ADMA could alter GCH1 protein and activity. Our data demonstrate that ADMA decreased GCH1 protein, but not mRNA concentrations, in pulmonary arterial endothelial cells (PAECs) because of the ubiquitination and proteasome-dependent degradation of GCH1. We also found that Hsp90-GCH1 interactions were reduced, whereas the association of GCH1 with Hsp70 and the C-terminus of Hsp70-interacting protein (CHIP) increased in ADMA-exposed PAECs. The overexpression of CHIP potentiated, whereas a CHIP U-box domain mutant attenuated, ADMA-induced GCH1 degradation and reductions in cellular BH(4) concentrations. We also found in vivo that Hsp90/GCH1 interactions are decreased, whereas GCH1-Hsp70 and GCH1-CHIP interactions and GCH1 ubiquitination are increased. Finally, we found that supplementation with l-arginine restored Hsp90-GCH1 interactions and increased both BH(4) and NO(x) concentrations in Shunt lambs. In conclusion, increased concentrations of ADMA can indirectly alter NO signaling through decreased cellular BH(4) concentrations, secondary to the disruption of Hsp90-GCH1 interactions and the CHIP-dependent proteasomal degradation of GCH1.
Sun
Xutong
X
Program in Pulmonary Vascular Disease, Vascular Biology Center, Medical College of Georgia, 1459 Laney Walker Blvd., CB3211B, Augusta, GA 30912, USA.
Fratz
Sohrab
S
Sharma
Shruti
S
Hou
Yali
Y
Rafikov
Ruslan
R
Kumar
Sanjiv
S
Rehmani
Imran
I
Tian
Jing
J
Smith
Anita
A
Schreiber
Christian
C
Reiser
Judith
J
Naumann
Susanne
S
Haag
Sebastian
S
Hess
John
J
Catravas
John D
JD
Patterson
Cam
C
Fineman
Jeffery R
JR
Black
Stephen M
SM
D000818:Animals; D000873:Anthracenes / Q000494:pharmacology; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D001783:Blood Flow Velocity / Q000187:drug effects; D004195:Disease Models, Animal; D005260:Female; D006136:GTP Cyclohydrolase / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D018841:HSP90 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D006330:Heart Defects, Congenital / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D008168:Lung / Q000098:blood supply* / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D011407:Propane / Q000031:analogs & derivatives / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D012756:Sheep
D000873:Anthracenes; D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; D009569:Nitric Oxide; C018524:N,N-dimethylarginine; D001120:Arginine; D019001:Nitric Oxide Synthase; D046988:Proteasome Endopeptidase Complex; D006136:GTP Cyclohydrolase; D011407:Propane