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Prostaglandin E2 inhibits renal collecting duct Na+ absorption by activating the EP1 receptor.

ABSTRACT: PGE2 exerts potent diuretic and natriuretic effects on the kidney. This action is mediated in part by direct inhibition of collecting duct Na+ absorption via a Ca++-coupled mechanism. These studies examine the role the Ca++-coupled PGE-E EP1 receptor plays in mediating these effects of PGE2 on Na+ transport. Rabbit EP1 receptor cDNA was amplified from rabbit kidney RNA. Nuclease protection assays demonstrated highest expression of EP1 mRNA in kidney, followed by stomach, adrenal, and ileum. In situ hybridization, demonstrated renal expression of EP1 mRNA was exclusively over the collecting duct. In fura-2-loaded microperfused rabbit cortical collecting duct, EP1 active PGE analogs were 10-1, 000-fold more potent in raising intracellular Ca++ than EP2, EP3, or EP4-selective compounds. Two different EP1 antagonists, AH6809 and SC19220, completely blocked the PGE2-stimulated intracellular calcium increase. AH6809 also completely blocked the inhibitory effect of PGE2 on Na+ absorption in microperfused rabbit cortical collecting ducts. These studies suggest that EP1 receptor activation mediates PGE2-dependent inhibition of Na+ absorption in the collecting duct, thereby contributing to its natriuretic effects.

SUBMITTER: Guan Y

PROVIDER: S-EPMC509081 | biostudies-other | 1998 Jul

REPOSITORIES: biostudies-other

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Prostaglandin E2 inhibits renal collecting duct Na+ absorption by activating the EP1 receptor.

Guan Y Y Zhang Y Y Breyer R M RM Fowler B B Davis L L Hébert R L RL Breyer M D MD

The Journal of clinical investigation 19980701 1

PGE2 exerts potent diuretic and natriuretic effects on the kidney. This action is mediated in part by direct inhibition of collecting duct Na+ absorption via a Ca++-coupled mechanism. These studies examine the role the Ca++-coupled PGE-E EP1 receptor plays in mediating these effects of PGE2 on Na+ transport. Rabbit EP1 receptor cDNA was amplified from rabbit kidney RNA. Nuclease protection assays demonstrated highest expression of EP1 mRNA in kidney, followed by stomach, adrenal, and ileum. In s ...[more]

PMID: 9649573

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Project description:Vasopressin controls water balance largely through PKA-dependent effects to regulate the collecting duct water channel aquaporin-2 (AQP2). Although considerable information has accrued regarding the regulation of water and solute transport in collecting duct cells, information is sparse regarding the signaling connections between PKA and transport responses. Here, we exploited recent advancements in protein mass spectrometry to perform a comprehensive, multiple-replicate analysis of changes in the phosphoproteome of native rat inner medullary collecting duct cells in response to the vasopressin V2 receptor-selective agonist 1-desamino-8D-arginine vasopressin. Of the 10,738 phosphopeptides quantified, only 156 phosphopeptides were significantly increased in abundance, and only 63 phosphopeptides were decreased, indicative of a highly selective response to vasopressin. The list of upregulated phosphosites showed several general characteristics: 1) a preponderance of sites with basic (positively charged) amino acids arginine (R) and lysine (K) in position -2 and -3 relative to the phosphorylated amino acid, consistent with phosphorylation by PKA and/or other basophilic kinases; 2) a greater-than-random likelihood of sites previously demonstrated to be phosphorylated by PKA; 3) a preponderance of sites in membrane proteins, consistent with regulation by membrane association; and 4) a greater-than-random likelihood of sites in proteins with class I COOH-terminal PDZ ligand motifs. The list of downregulated phosphosites showed a preponderance of those with proline in position +1 relative to the phosphorylated amino acid, consistent with either downregulation of proline-directed kinases (e.g., MAPKs or cyclin-dependent kinases) or upregulation of one or more protein phosphatases that selectively dephosphorylate such sites (e.g., protein phosphatase 2A). The phosphoproteomic data were used to create a web resource for the investigation of G protein-coupled receptor signaling and regulation of AQP2-mediated water transport.

Project description:Tolvaptan, a vasopressin antagonist selective for the V2-subtype vasopressin receptor (V2R), is widely used in the treatment of hyponatremia and autosomal-dominant polycystic kidney disease (ADPKD). Its effects on signaling in collecting duct cells have not been fully characterized. Here, we perform RNA-seq in a collecting duct cell line (mpkCCD). The data show that tolvaptan inhibits the expression of mRNAs that were previously shown to be increased in response to vasopressin including aquaporin-2, but also reveals mRNA changes that were not readily predictable and suggest off-target actions of tolvaptan. One such action is activation of the MAPK kinase (ERK1/ERK2) pathway. Prior studies have shown that ERK1/ERK2 activation is essential in the regulation of a variety of cellular and physiological processes and can be associated with cell proliferation. In immunoblotting experiments, we demonstrated that ERK1/ERK2 phosphorylation in mpkCCD cells was significantly reduced by vasopressin, in contrast to the increases seen in non-collecting-duct cells overexpressing V2R in prior studies. We also found that tolvaptan has a strong effect to increase ERK1/ERK2 phosphorylation in the presence of vasopressin and that tolvaptan's effect to increase ERK1/ERK2 phosphorylation is absent in mpkCCD cells in which both protein kinase A (PKA)-catalytic subunits have been deleted. Thus, it appears that the tolvaptan effect to increase ERK activation is PKA-dependent and is not due to an off-target effect of tolvaptan. We conclude that in cells expressing V2R at endogenous levels: 1) vasopressin decreases ERK1/ERK2 activation; 2) in the presence of vasopressin, tolvaptan increases ERK1/ERK2 activation; and 3) these effects are PKA-dependent.NEW & NOTEWORTHY Vasopressin is a key hormone that regulates the function of the collecting duct of the kidney. ERK1 and ERK2 are enzymes that play key roles in physiological regulation in all cells. The authors used collecting duct cell cultures to investigate the effects of vasopressin and the vasopressin receptor antagonist tolvaptan on ERK1 and ERK2 phosphorylation and activation.

Dataset Information

Prostaglandin E2 inhibits renal collecting duct Na+ absorption by activating the EP1 receptor.

Publications

Prostaglandin E2 inhibits renal collecting duct Na+ absorption by activating the EP1 receptor.

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