C-terminus of heat shock protein 70-interacting protein-dependent GTP cyclohydrolase I degradation in lambs with increased pulmonary blood flow

Xutong Sun, Sohrab Fratz, Shruti Sharma, Yali Hou, Ruslan Rafikov, Sanjiv Kumar, Imran Rehmani, Jing Tian, Anita Smith, Christian Schreiber, Judith Reiser, Susanne Naumann, Sebastian Haag, John Hess, John D. Catravas, Cam Patterson, Jeffery R. Fineman, Stephen M. Black

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


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 (BH4) 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-limitingenzyme in the generation of BH4, 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 BH4 concentrations.Wealso 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 BH4 and NOx concentrations in Shunt lambs. In conclusion, increased concentrations of ADMA can indirectly alter NO signaling through decreased cellular BH4 concentrations, secondary to the disruption of Hsp90-GCH1 interactions and the CHIP-dependent proteasomal degradation of GCH1.

Original languageEnglish (US)
Pages (from-to)163-171
Number of pages9
JournalAmerican journal of respiratory cell and molecular biology
Issue number1
StatePublished - Jul 1 2011
Externally publishedYes


  • Hsp70
  • Hsp90
  • Mitochondrial dysfunction
  • Proteasome
  • Ubiquitination

ASJC Scopus subject areas

  • Molecular Biology
  • Pulmonary and Respiratory Medicine
  • Clinical Biochemistry
  • Cell Biology


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