title: Involvement of cAMP/cAMP-dependent protein kinase signaling pathway in regulation of Na+,K+-ATPase upon activation of opioid receptors by morphine.
abstract: The depolarization of neurons induced by impairment of Na+,K+-ATPase activity after long-term opiate treatment has been shown to involve the development of opioid dependence. However, the mechanisms underlying changes in Na+,K+-ATPase activity after opioid treatment are unclear. The best-established molecular adaptation to long-term opioid exposure is up-regulation of the cAMP/cAMP-dependent protein kinase (PKA) signaling pathway; this study, therefore, was undertaken to investigate the role of up-regulation of cAMP/PKA signaling pathway in alteration of the mouse hippocampal Na+,K+-ATPase activity. The results demonstrated that short-term morphine treatment dose dependently stimulated Na+,K+-ATPase activity. This action could be significantly suppressed by adenylyl cyclase activator 7beta-acetoxy-8,13-epoxy-1alpha,6beta,9alpha-trihydroxylabd-14-en-11-one (forskolin), or the cAMP analog dibutyryl-cAMP. Contrary to short-term morphine treatment, long-term treatment significantly inhibited Na+,K+-ATPase activity. Moreover, an additional decrease in Na+,K+-ATPase activity was observed by naloxone precipitation. The effects of both short- and long-term morphine treatment on Na+,K+-ATPase activity were naltrexone-reversible. The regulation of Na+,K+-ATPase activity by morphine was inversely correlated with intracellular cAMP accumulation. N-[2-(4-Bromocinnamylamino)ethyl]-5-isoquinoline (H89), a specific PKA inhibitor, mimicked the stimulatory effect of short-term morphine but antagonized the inhibitory effect of long-term morphine treatment on Na+,K+-ATPase activity. However, okadaic acid, a protein phosphatase inhibitor, suppressed short-term morphine stimulation but potentiated long-term morphine inhibition of Na+,K+-ATPase activity. The regulation of Na+,K+-ATPase activity by morphine treatment seemed to associate with the alteration in phosphorylation level but not to be relevant to the change in abundance of Na+,K+-ATPase. These findings strongly demonstrate that cAMP/PKA signaling pathway involves regulation of Na+,K+-ATPase activity after activation of opioid receptors.
authors.affiliation: State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, No.555 Zuchongzhi Rd., Shanghai 201203, China.
authors.forename: Zhao-Qiu
authors.initials: ZQ
authors.lastname: Wu
authors.forename: Mu
authors.initials: M
authors.lastname: Li
authors.forename: Jie
authors.initials: J
authors.lastname: Chen
authors.forename: Zhi-Qiang
authors.initials: ZQ
authors.lastname: Chi
authors.forename: Jing-Gen
authors.initials: JG
authors.lastname: Liu
mesh_terms: D000262:Adenylyl Cyclases; D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D015536:Down-Regulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism; D007546:Isoquinolines / Q000494:pharmacology; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D018716:Molecular Mimicry; D009020:Morphine / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D009271:Naltrexone / Q000494:pharmacology; D019319:Okadaic Acid / Q000494:pharmacology; D037342:Pertussis Toxin / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors; D014176:Protein Biosynthesis / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011957:Receptors, Opioid / Q000819:agonists*; D015398:Signal Transduction; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013449:Sulfonamides / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D007546:Isoquinolines; D047428:Protein Kinase Inhibitors; D011957:Receptors, Opioid; D013449:Sulfonamides; D019319:Okadaic Acid; D009271:Naltrexone; D009020:Morphine; D000242:Cyclic AMP; D037342:Pertussis Toxin; D017868:Cyclic AMP-Dependent Protein Kinases; D010749:Phosphoprotein Phosphatases; D000262:Adenylyl Cyclases; D000254:Sodium-Potassium-Exchanging ATPase; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide