Uroguanylin modulates (Na++K+)ATPase in a proximal tubule cell line: Interactions among the cGMP/protein kinase G, cAMP/protein kinase A, and mTOR pathways

• Published in: Biochimica et biophysica acta Vol. 1860; no. 7; pp. 1431 - 1438
• Main Authors: Arnaud-Batista, Francisco J., Peruchetti, Diogo B., Abreu, Thiago P., do Nascimento, Nilberto R.F., Malnic, Gerhard, Fonteles, Manasses C., Caruso-Neves, Celso
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.07.2016
• Subjects: absorption; adenosine triphosphate; Adenosine Triphosphate - metabolism; adenosinetriphosphatase; Animals; cAMP-dependent protein kinase; Cell signaling; cGMP-dependent protein kinase; cyclic AMP; Cyclic AMP - metabolism; Cyclic AMP-Dependent Protein Kinases - antagonists & inhibitors; Cyclic AMP-Dependent Protein Kinases - metabolism; cyclic GMP; Cyclic GMP - metabolism; Cyclic GMP-Dependent Protein Kinases - antagonists & inhibitors; Cyclic GMP-Dependent Protein Kinases - metabolism; Dose-Response Relationship, Drug; Enzyme Activation; enzyme inhibition; excretion; Hydrolysis; immunoblotting; Kidney; Kidney Tubules, Proximal - drug effects; Kidney Tubules, Proximal - enzymology; LLC-PK1 Cells; mechanism of action; Natriuresis - drug effects; Natriuretic Agents - pharmacology; Natriuretic Peptides - pharmacology; Phosphorylation; Protein Kinase Inhibitors - pharmacology; Proximal tubule; Renal Elimination - drug effects; Renal Reabsorption - drug effects; Second Messenger Systems - drug effects; signal transduction; sodium; Sodium - metabolism; Sodium pump; Sodium reabsorption; sodium-potassium-exchanging ATPase; Sodium-Potassium-Exchanging ATPase - metabolism; Swine; TOR Serine-Threonine Kinases - antagonists & inhibitors; TOR Serine-Threonine Kinases - metabolism; Uroguanylin; Gi; db-cAMP; PT; PKB; PKA; S6K; Sodium pump; Uroguanylin; NHE3; Sodium reabsorption; PKG; Cell signaling; Kidney; Proximal tubule; GFR; 8-Br-cGMP; mTOR; mTORC2; UGN; mTORC1
• ISSN: 0304-4165; 0006-3002; 1872-8006
• DOI: 10.1016/j.bbagen.2016.04.012

The natriuretic effect of uroguanylin (UGN) involves reduction of proximal tubule (PT) sodium reabsorption. However, the target sodium transporters as well as the molecular mechanisms involved in these processes remain poorly understood. To address the effects of UGN on PT (Na++K+)ATPase and the signal transduction pathways involved in this effect, we used LLC-PK1 cells. The effects of UGN were determined through ouabain-sensitive ATP hydrolysis and immunoblotting assays during different experimental conditions. We observed that UGN triggers cGMP/PKG and cAMP/PKA pathways in a sequential way. The activation of PKA leads to the inhibition of mTORC2 activity, PKB phosphorylation at S473, PKB activity and, consequently, a decrease in the mTORC1/S6K pathway. The final effects are decreased expression of the α1 subunit of (Na++K+)ATPase and inhibition of enzyme activity. These results suggest that the molecular mechanism of action of UGN on sodium reabsorption in PT cells is more complex than previously thought. We propose that PKG-dependent activation of PKA leads to the inhibition of the mTORC2/PKB/mTORC1/S6K pathway, an important signaling pathway involved in the maintenance of the PT sodium pump expression and activity. The current results expand our understanding of the signal transduction pathways involved in the overall effect of UGN on renal sodium excretion. •The molecular mechanism of UGN on PT cells is more complex than previously thought.•UGN decreased the expression of the (Na++K+)ATPase α1 subunit and enzyme activity.•The molecular mechanism involves PKG-dependent activation of the PKA pathway.•PKA activated by UGN leads to the inhibition of the mTORC2/PKB/mTORC1/S6K pathway.