Early targets of lithium in rat kidney inner medullary collecting duct include p38 and ERK1/2.
Almost half of patients receiving lithium salts have nephrogenic diabetes insipidus. Chronic lithium exposure induces AQP2 downregulation and changes in the cellular composition of the collecting duct. In order to understand these pathophysiological events, we determined the earliest lithium targets in rat inner medullary collecting duct (IMCD) by examining changes in the IMCD phosphoproteome after acute lithium administration. IMCDs were isolated 9 h after lithium exposure, a time when urinary concentrating impairment was evident. We found 1093 unique phosphopeptides corresponding to 492 phosphoproteins identified and quantified by mass spectrometry. Label-free quantification identified 152 upregulated and 56 downregulated phosphopeptides in response to lithium. Bioinformatic analysis highlighted several signaling proteins including MAP kinases and cell-junction proteins. The majority of the upregulated phosphopeptides contained a proline-directed motif, a known target of MAPK. Four hours after lithium exposure, phosphorylation sites in the activation loops of ERK1/2 and p38 were upregulated. Increased expression of phospho-Ser261-AQP2 (proline-directed motif) was concomitant with the increase in urine output. Pretreatment with MAPK inhibitors reversed the increased Ser261-AQP2 phosphorylation. Thus, in IMCD, ERK1/2 and p38 are early targets of lithium and may play a role in the onset of lithium-induced polyuria.
1] Water and Salt Research Center, Department of Biomedicine, Aarhus University, Aarhus C, Denmark [2] Division of Nephrology, Department of Cardiothoracic and Respiratory Sciences, Second University of Naples, Naples, Italy.
Francesco
F
Trepiccione
1] Epithelial Systems Biology Laboratory, National Heart, Lung, and Blood Institute (NHLBI), National Institutes of Health, Bethesda, Maryland, USA [2] Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
Trairak
T
Pisitkun
Epithelial Systems Biology Laboratory, National Heart, Lung, and Blood Institute (NHLBI), National Institutes of Health, Bethesda, Maryland, USA.
Jason D
JD
Hoffert
Water and Salt Research Center, Department of Biomedicine, Aarhus University, Aarhus C, Denmark.
Søren B
SB
Poulsen
Division of Nephrology, Department of Cardiothoracic and Respiratory Sciences, Second University of Naples, Naples, Italy.
Giovambattista
G
Capasso
Water and Salt Research Center, Department of Biomedicine, Aarhus University, Aarhus C, Denmark.
Søren
S
Nielsen
Epithelial Systems Biology Laboratory, National Heart, Lung, and Blood Institute (NHLBI), National Institutes of Health, Bethesda, Maryland, USA.
Mark A
MA
Knepper
Water and Salt Research Center, Department of Biomedicine, Aarhus University, Aarhus C, Denmark.
Robert A
RA
Fenton
Water and Salt Research Center, Department of Biomedicine, Aarhus University, Aarhus C, Denmark.
Birgitte M
BM
Christensen
D000818:Animals; D018500:Diabetes Insipidus, Nephrogenic / Q000139:chemically induced; D015536:Down-Regulation / Q000187:drug effects; D007685:Kidney Tubules, Collecting / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D018020:Lithium Compounds / Q000009:adverse effects / Q000494:pharmacology*; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D008297:Male; D013058:Mass Spectrometry; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D054730:Protein Interaction Domains and Motifs; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D020543:Proteome / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D015854:Up-Regulation / Q000187:drug effects; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
D018020:Lithium Compounds; D010750:Phosphoproteins; D047428:Protein Kinase Inhibitors; D020543:Proteome; D019950:Mitogen-Activated Protein Kinase 1; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases