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.
Carraro-Lacroix
Luciene R
LR
Department of Physiology and Biophysics, Institute of Biomedical Sciences, Federal University of São Paulo, São Paulo, Brazil.
Malnic
Gerhard
G
Girardi
Adriana C C
AC
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