title: Increased degradation of MYPT1 contributes to the development of tolerance to nitric oxide in porcine pulmonary artery.
abstract: Myosin phosphatase target subunit 1 (MYPT1) is the regulatory subunit of myosin light chain phosphatase (MLCP). It plays a critical role in vasodilatation induced by cGMP-elevating agents such as nitric oxide (NO). The present study was performed to determine the role of MYPT1 in the development of tolerance of the pulmonary artery to NO. Incubation of isolated porcine pulmonary arteries for 24 or 48 h with DETA NONOate (DETA NO) significantly reduced protein levels of MYPT1 and the leucine zipper-positive (LZ+) isoform of MYPT1 but not that of PP1cdelta. The extent of reduction in total MYPT1 protein level was comparable to that of MYPT1 (LZ+). The decrease in MYPT1 protein caused by 48-h DETA NO incubation was prevented by ODQ, an inhibitor of guanylyl cyclase, and by inhibitors of proteasomes (MG-132 and lactacystin) but was not affected by the inhibitor of protein synthesis, cycloheximide. A reduction in MYPT1 protein was also obtained with 8-bromo-cGMP, but this was prevented by Rp-8-bromo-PET-cGMP [inhibitor of cGMP-dependent protein kinase (PKG)]. Incubation for 48 h with DETA NO also reduced dephosphorylation of myosin light chain and relaxation of the artery in response to DETA NO, which was prevented by MG-132. These results suggest that the reduction in MYPT1 protein contributes to the development of tolerance of pulmonary arteries to NO. This may result from increased degradation of MYPT1 after prolonged PKG activation.
authors.affiliation: Department of Physiology and Pathophysiology, Peking University Health Science Center, Beijing, China.
authors.forename: Huijuan
authors.initials: H
authors.lastname: Ma
authors.forename: Qiong
authors.initials: Q
authors.lastname: He
authors.forename: Dou
authors.initials: D
authors.lastname: Dou
authors.forename: Xiaoxu
authors.initials: X
authors.lastname: Zheng
authors.forename: Lei
authors.initials: L
authors.lastname: Ying
authors.forename: Yuming
authors.initials: Y
authors.lastname: Wu
authors.forename: J Usha
authors.initials: JU
authors.lastname: Raj
authors.forename: Yuansheng
authors.initials: Y
authors.lastname: Gao
mesh_terms: D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008168:Lung / Q000098:blood supply / Q000378:metabolism; D043263:Myosin-Light-Chain Phosphatase / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D010069:Oxadiazoles / Q000494:pharmacology; D020033:Protein Isoforms / Q000378:metabolism*; D054645:Protein Phosphatase 1 / Q000378:metabolism*; D011651:Pulmonary Artery / Q000187:drug effects / Q000378:metabolism*; D011810:Quinoxalines / Q000494:pharmacology; D013552:Swine; D014226:Triazenes / Q000494:pharmacology; D014662:Vasoconstrictor Agents / Q000494:pharmacology
chemical_list: C105351:1-hydroxy-2-oxo-3,3-bis(2-aminoethyl)-1-triazene; C095284:1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one; D004791:Enzyme Inhibitors; D020030:Nitric Oxide Donors; D010069:Oxadiazoles; D020033:Protein Isoforms; D011810:Quinoxalines; D014226:Triazenes; D014662:Vasoconstrictor Agents; D015124:8-Bromo Cyclic Adenosine Monophosphate; C016276:8-bromocyclic GMP; D009569:Nitric Oxide; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; C499850:Ppp1r12a protein, rat; D054645:Protein Phosphatase 1; D043263:Myosin-Light-Chain Phosphatase; D006152:Cyclic GMP