TY - JOUR
T1 - Tissue-specific regulation of sodium/proton exchanger isoform 3 activity in Na+/H+ Exchanger Regulatory Factor 1 (NHERF1) null mice
T2 - cAMP inhibition is differentially dependent on NHERF1 and exchange protein directly activated by cAMP in ileum versus proximal tubule
AU - Murtazina, Rakhilya
AU - Kovbasnjuk, Olga
AU - Zachos, Nicholas C.
AU - Li, Xuhang
AU - Chen, Yueping
AU - Hubbard, Ann
AU - Hogema, Boris M.
AU - Steplock, Deborah
AU - Seidler, Ursula
AU - Hoque, Kazi M.
AU - Chung, Ming Tse
AU - De Jonge, Hugo R.
AU - Weinman, Edward J.
AU - Donowitz, M.
PY - 2007/8/24
Y1 - 2007/8/24
N2 - The multi-PDZ domain containing protein Na+/H+ Exchanger Regulatory Factor 1 (NHERF1) binds to Na+/H+ exchanger 3 (NHE3) and is associated with the brush border (BB) membrane of murine kidney and small intestine. Although studies in BB isolated from kidney cortex of wild type and NHERF1-/- mice have shown that NHERF1 is necessary for cAMP inhibition of NHE3 activity, a role of NHERF1 in NHE3 regulation in small intestine and in intact kidney has not been established. Here a method using multi-photon microscopy with the pH-sensitive dye SNARF-4F (carboxyse-minaphthorhodafluors-4F) to measure BB NHE3 activity in intact murine tissue and use it to examine the role of NHERF1 in regulation of NHE3 activity. NHE3 activity in wild type and NHERF1-/- ileum and wild type kidney cortex were inhibited by cAMP, whereas the cAMP effect was abolished in kidney cortex of NHERF1-/- mice. cAMP inhibition of NHE3 activity in these two tissues is mediated by different mechanisms. In ileum, a protein kinase A (PKA)-dependent mechanism accounts for all cAMP inhibition of NHE3 activity since the PKA antagonist H-89 abolished the inhibitory effect of cAMP. In kidney, both PKA-dependent and non-PKA-dependent mechanisms were involved, with the latter reproduced by the effect on an EPAC (exchange protein directly activated by cAMP) agonist (8-(4-chlorophenylthio)-2′O-Me-cAMP). In contrast, the EPAC agonist had no effect in proximal tubules in NHERF1 -/- mice. These data suggest that in proximal tubule, NHERF1 is required for all cAMP inhibition of NHE3, which occurs through both EPAC-dependent and PKA-dependent mechanisms; in contrast, cAMP inhibits ileal NHE3 only by a PKA-dependent pathway, which is independent of NHERF1 and EPAC.
AB - The multi-PDZ domain containing protein Na+/H+ Exchanger Regulatory Factor 1 (NHERF1) binds to Na+/H+ exchanger 3 (NHE3) and is associated with the brush border (BB) membrane of murine kidney and small intestine. Although studies in BB isolated from kidney cortex of wild type and NHERF1-/- mice have shown that NHERF1 is necessary for cAMP inhibition of NHE3 activity, a role of NHERF1 in NHE3 regulation in small intestine and in intact kidney has not been established. Here a method using multi-photon microscopy with the pH-sensitive dye SNARF-4F (carboxyse-minaphthorhodafluors-4F) to measure BB NHE3 activity in intact murine tissue and use it to examine the role of NHERF1 in regulation of NHE3 activity. NHE3 activity in wild type and NHERF1-/- ileum and wild type kidney cortex were inhibited by cAMP, whereas the cAMP effect was abolished in kidney cortex of NHERF1-/- mice. cAMP inhibition of NHE3 activity in these two tissues is mediated by different mechanisms. In ileum, a protein kinase A (PKA)-dependent mechanism accounts for all cAMP inhibition of NHE3 activity since the PKA antagonist H-89 abolished the inhibitory effect of cAMP. In kidney, both PKA-dependent and non-PKA-dependent mechanisms were involved, with the latter reproduced by the effect on an EPAC (exchange protein directly activated by cAMP) agonist (8-(4-chlorophenylthio)-2′O-Me-cAMP). In contrast, the EPAC agonist had no effect in proximal tubules in NHERF1 -/- mice. These data suggest that in proximal tubule, NHERF1 is required for all cAMP inhibition of NHE3, which occurs through both EPAC-dependent and PKA-dependent mechanisms; in contrast, cAMP inhibits ileal NHE3 only by a PKA-dependent pathway, which is independent of NHERF1 and EPAC.
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U2 - 10.1074/jbc.M701910200
DO - 10.1074/jbc.M701910200
M3 - Article
C2 - 17580307
AN - SCOPUS:34548314536
SN - 0021-9258
VL - 282
SP - 25141
EP - 25151
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 34
ER -