Regulation of Na+/H+ exchanger NHE3 by glucagon-like peptide 1 receptor agonist exendin-4 in renal proximal tubule cells.
The gut incretin hormone glucagon-like peptide 1 (GLP-1) is released in response to ingested nutrients and enhances insulin secretion. In addition to its insulinotropic properties, GLP-1 has been shown to have natriuretic actions paralleled by a diminished proton secretion. We therefore studied the role of the GLP-1 receptor agonist exendin-4 in modulating the activity of Na(+)/H(+) exchanger NHE3 in LLC-PK(1) cells. We found that NHE3-mediated Na(+)-dependent intracellular pH (pH(i)) recovery decreased approximately 50% after 30-min treatment with 1 nM exendin-4. Pharmacological inhibitors and cAMP analogs that selectively activate protein kinase A (PKA) or the exchange protein directly activated by cAMP (EPAC) demonstrated that regulation of NHE3 activity by exendin-4 requires activation of both cAMP downstream effectors. This conclusion was based on the following observations: 1) the PKA antagonist H-89 completely prevented the effect of the PKA activator but only partially blocked the exendin-4-induced NHE3 inhibition; 2) the MEK1/2 inhibitor U-0126 abolished the effect of the EPAC activator but only diminished the exendin-4-induced NHE3 inhibition; 3) combination of H-89 and U-0126 fully prevented the effect of exendin-4 on NHE3; 4) no additive effect in the inhibition of NHE3 activity was observed when exendin-4, PKA, and EPAC activators were used together. Mechanistically, the inhibitory effect of exendin-4 on pH(i) recovery was associated with an increase of NHE3 phosphorylation. Conversely, this inhibition took place without changes in the surface expression of the transporter. We conclude that GLP-1 receptor agonists modulate sodium homeostasis in the kidney, most likely by affecting NHE3 activity.
Department of Physiology and Biophysics, Institute of Biomedical Sciences, Federal University of São Paulo, São Paulo, Brazil.
Luciene R
LR
Carraro-Lacroix
Gerhard
G
Malnic
Adriana C C
AC
Girardi
D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D000077270:Exenatide; D000067757:Glucagon-Like Peptide-1 Receptor; D006706:Homeostasis / Q000187:drug effects; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D007425:Intracellular Membranes / Q000378:metabolism; D007546:Isoquinolines / Q000494:pharmacology; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D018374:LLC-PK1 Cells; D010455:Peptides / Q000494:pharmacology*; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051381:Rats; D018027:Receptors, Glucagon / Q000819:agonists*; D015398:Signal Transduction / Q000502:physiology; D012964:Sodium / Q000378:metabolism; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*; D013449:Sulfonamides / Q000494:pharmacology; D013552:Swine; D014688:Venoms / Q000494:pharmacology*
C000593835:Glp1r protein, rat; D000067757:Glucagon-Like Peptide-1 Receptor; D007546:Isoquinolines; D010455:Peptides; D047428:Protein Kinase Inhibitors; D018027:Receptors, Glucagon; C000613387:Slc9a3 protein, rat; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; D013449:Sulfonamides; D014688:Venoms; D012964:Sodium; D000077270:Exenatide; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide