Authors: A Bagorda L Guerra F Di Sole C HelmleKolb M Favia KA Jacobson V Casavola SJ Reshkin
Publish Date: 2014/03/18
Volume: 188, Issue: 3, Pages: 249-259
Abstract
As potential autocrine or paracrine factors extracellular nucleotides are known to be important regulators of renal ion transporters by activating cell surface receptors and intracellular signaling pathways We investigated the influence of extracellular adenine nucleotides on Na+/H+ exchanger isoform 3 NHE3 activity in A6NHE3 cells This is a polarized cell line obtained by stable transfection of A6 cells with the cDNA encoding the rat isoform of NHE3 which is expressed on the apical membrane Basolateral addition of the P2Y1 agonist 2MeSADP induced an inhibition of NHE3 activity which was prevented by preincubation with selective P2Y1 antagonists MRS 2179 N6methyl2deoxyadenosine35bisphosphate and MRS 2286 222chloro6methylaminopurin9ylethylpropane13bisoxydiammoniumphosphate NHE3 activity was also significantly inhibited by ATP and ATPgS but not by UTP 2MeSADP induced a P2Y1 antagonistsensitive increase in both Ca2+i and cAMP production Preincubation with a PKC inhibitor Calphostin C or the calcium chelator BAPTAAM had no effect on the 2MeSADPdependent inhibition of NHE3 activity whereas this inhibition was reversed by either incubation with the PKA inhibitor H89 or by mutation of two PKA target serines S552 and S605 on NHE3 Preincubation of the A6NHE3 cells with the synthetic peptide Ht31 which prevents the binding between AKAPs and the regulatory PKA subunits RII also prevented the 2MeSADPinduced inhibition of NHE3 We conclude that only the cAMP/PKA pathway is involved in the inhibition of NHE3 activity
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