title: Activation of the metabolic sensor AMP-activated protein kinase inhibits aquaporin-2 function in kidney principal cells.
abstract: Aquaporin-2 (AQP2) is essential to maintain body water homeostasis. AQP2 traffics from intracellular vesicles to the apical membrane of kidney collecting duct principal cells in response to vasopressin [arginine vasopressin (AVP)], a hormone released with low intravascular volume, which causes decreased kidney perfusion. Decreased kidney perfusion activates AMP-activated kinase (AMPK), a metabolic sensor that inhibits the activity of several transport proteins. We hypothesized that AMPK activation also inhibits AQP2 function. These putative AMPK effects could protect interstitial ionic gradients required for urinary concentration during metabolic stress when low intravascular volume induces AVP release. Here we found that short-term AMPK activation by treatment with 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside (AICAR; 75 min) in kidney tissue prevented baseline AQP2 apical accumulation in principal cells, but did not prevent AQP2 apical accumulation in response to the AVP analog desmopressin (dDAVP). Prolonged AMPK activation prevented AQP2 cell membrane accumulation in response to forskolin in mouse collecting duct mpkCCDc14cells. Moreover, AMPK inhibition accelerated hypotonic lysis of Xenopus oocytes expressing AQP2. We performed phosphorylation assays to elucidate the mechanism by which AMPK regulates AQP2. Although AMPK weakly phosphorylated immunoprecipitated AQP2 in vitro, no direct AMPK phosphorylation of the AQP2 COOH-terminus was detected by mass spectrometry. AMPK promoted Ser-261 phosphorylation and antagonized dDAVP-dependent phosphorylation of other AQP2 COOH-terminal sites in cells. Our findings suggest an increasing, time-dependent antagonism of AMPK on AQP2 regulation with AICAR-dependent inhibition of cAMP-dependent apical accumulation and AVP-dependent phosphorylation of AQP2. This inhibition likely occurs via a mechanism that does not involve direct AQP2 phosphorylation by AMPK.
authors.affiliation: Department of Medicine, Renal-Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.
authors.forename: Mohammad M
authors.initials: MM
authors.lastname: Al-Bataineh
authors.affiliation: Department of Medicine, University of Southern California/University Kidney Research Organization, Kidney Research Center, Division of Nephrology and Hypertension, Keck School of Medicine of University of Southern California, Los Angeles, California.
authors.forename: Hui
authors.initials: H
authors.lastname: Li
authors.affiliation: Department of Medicine, University of Southern California/University Kidney Research Organization, Kidney Research Center, Division of Nephrology and Hypertension, Keck School of Medicine of University of Southern California, Los Angeles, California.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Ohmi
authors.affiliation: Department of Medicine, Renal-Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.
authors.forename: Fan
authors.initials: F
authors.lastname: Gong
authors.affiliation: Department of Medicine, Renal-Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.
authors.forename: Allison L
authors.initials: AL
authors.lastname: Marciszyn
authors.affiliation: Department of Medicine, Renal-Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.
authors.forename: Sajid
authors.initials: S
authors.lastname: Naveed
authors.affiliation: Department of Molecular Genetics, School for Cardiovascular Diseases, Maastricht University, Maastricht, The Netherlands; and.
authors.forename: Xiaoqing
authors.initials: X
authors.lastname: Zhu
authors.affiliation: Department of Molecular Genetics, School for Cardiovascular Diseases, Maastricht University, Maastricht, The Netherlands; and.
authors.forename: Dietbert
authors.initials: D
authors.lastname: Neumann
authors.affiliation: Department of Biomedicine, InterPrET Center, Aarhus University, Aarhus, Denmark.
authors.forename: Qi
authors.initials: Q
authors.lastname: Wu
authors.affiliation: Department of Biomedicine, InterPrET Center, Aarhus University, Aarhus, Denmark.
authors.forename: Lei
authors.initials: L
authors.lastname: Cheng
authors.affiliation: Department of Biomedicine, InterPrET Center, Aarhus University, Aarhus, Denmark.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Fenton
authors.affiliation: Department of Medicine, University of Southern California/University Kidney Research Organization, Kidney Research Center, Division of Nephrology and Hypertension, Keck School of Medicine of University of Southern California, Los Angeles, California; nuria.pastor-soler@med.usc.edu.
authors.forename: Núria M
authors.initials: NM
authors.lastname: Pastor-Soler
authors.affiliation: Department of Medicine, University of Southern California/University Kidney Research Organization, Kidney Research Center, Division of Nephrology and Hypertension, Keck School of Medicine of University of Southern California, Los Angeles, California.
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: Hallows
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D051399:Aquaporin 2 / Q000378:metabolism*; D002460:Cell Line; D007668:Kidney / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051379:Mice; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D012265:Ribonucleotides / Q000494:pharmacology; D014981:Xenopus
chemical_list: D051399:Aquaporin 2; D012265:Ribonucleotides; D000620:Aminoimidazole Carboxamide; D055372:AMP-Activated Protein Kinases; C031143:AICA ribonucleotide
keywords: PKA; epithelial; metformin; mpkCCDc14; water transport