Asymmetric Dimethylarginine Stimulates Akt1 Phosphorylation via Heat Shock Protein 70-Facilitated Carboxyl-Terminal Modulator Protein Degradation in Pulmonary Arterial Endothelial Cells.

TitleAsymmetric Dimethylarginine Stimulates Akt1 Phosphorylation via Heat Shock Protein 70-Facilitated Carboxyl-Terminal Modulator Protein Degradation in Pulmonary Arterial Endothelial Cells.
Publication TypeJournal Article
Year of Publication2016
AuthorsSun X, Kellner M, Desai AA, Wang T, Lu Q, Kangath A, Qu N, Klinger C, Fratz S, Yuan JX-J, Jacobson JR, Garcia JGN, Rafikov R, Fineman JR, Black SM
JournalAm J Respir Cell Mol Biol
Volume55
Issue2
Pagination275-87
Date Published2016 Aug
ISSN Number1535-4989
KeywordsAnimals, Arginine, Carrier Proteins, Disease Models, Animal, Endothelial Cells, Genes, Dominant, HSP70 Heat-Shock Proteins, HSP90 Heat-Shock Proteins, Lung, Mitochondria, Nitric Oxide Synthase Type III, Phosphorylation, Proteasome Endopeptidase Complex, Protein Binding, Proteolysis, Proto-Oncogene Proteins c-akt, Pulmonary Artery, Regional Blood Flow, Sheep, Ubiquitination
Abstract

<p>Asymmetric dimethylarginine (ADMA) induces the mitochondrial translocation of endothelial nitric oxide synthase (eNOS) through the nitration-mediated activation of Akt1. However, it is recognized that the activation of Akt1 requires phosphorylation events at threonine (T) 308 and serine (S) 473. Thus, the current study was performed to elucidate the potential effect of ADMA on Akt1 phosphorylation and the mechanisms that are involved. Exposure of pulmonary arterial endothelial cells to ADMA enhanced Akt1 phosphorylation at both threonine 308 and Ser473 without altering Akt1 protein levels, phosphatase and tensin homolog activity, or membrane Akt1 levels. Heat shock protein (Hsp) 90 plays a pivotal role in maintaining Akt1 activity, and our results demonstrate that ADMA decreased Hsp90-Akt1 interactions, but, surprisingly, overexpression of a dominant-negative Hsp90 mutant increased Akt1 phosphorylation. ADMA exposure or overexpression of dominant-negative Hsp90 increased Hsp70 levels, and depletion of Hsp70 abolished ADMA-induced Akt1 phosphorylation. ADMA decreased the interaction of Akt1 with its endogenous inhibitor, carboxyl-terminal modulator protein (CTMP). This was mediated by the proteasomal-dependent degradation of CTMP. The overexpression of CTMP attenuated ADMA-induced Akt1 phosphorylation at Ser473, eNOS phosphorylation at Ser617, and eNOS mitochondrial translocation. Finally, we found that the mitochondrial translocation of eNOS in our lamb model of pulmonary hypertension is associated with increased Akt1 and eNOS phosphorylation and reduced Akt1-CTMP protein interactions. In conclusion, our data suggest that CTMP is directly involved in ADMA-induced Akt1 phosphorylation in vitro and in vivo, and that increasing CTMP levels may be an avenue to treat pulmonary hypertension.</p>

DOI10.1165/rcmb.2015-0185OC
Alternate JournalAm. J. Respir. Cell Mol. Biol.
PubMed ID26959555
PubMed Central IDPMC4979361
Grant ListP30 ES006694 / ES / NIEHS NIH HHS / United States
P01 HL101902 / HL / NHLBI NIH HHS / United States
R01 HL061284 / HL / NHLBI NIH HHS / United States
R01 HD039110 / HD / NICHD NIH HHS / United States
R01 HL067841 / HL / NHLBI NIH HHS / United States
R01 HL060190 / HL / NHLBI NIH HHS / United States