NHERF2 is necessary for basal activity, second messenger inhibition, and LPA stimulation of NHE3 in mouse distal ileum

Rakhilya Murtazina, Olga Kovbasnjuk, Tian E. Chen, Nicholas C. Zachos, Yeuping Chen, Hetal S. Kocinsky, Boris M. Hogema, Ursula Seidler, Hugo R. de Jonge, Mark Donowitz

Research output: Contribution to journalArticlepeer-review

Abstract

To test the hypothesis that Na+/H+ exchanger (NHE) regulatory factor 2 (NHERF2) is necessary for multiple aspects of acute regulation of NHE3 in intact mouse small intestine, distal ileal NHE3 activity was determined using two-photon microscopy/SNARF-4F in a NHERF2-null mouse model. The NHERF2-null mouse ileum had shorter villi, deeper crypts, and decreased epithelial cell number. Basal rates of NHE3 activity were reduced in NHERF2-null mice, which was associated with a reduced percentage of NHE3 in the apical domain and an increase in intracellular NHE3 amount but no change in total level of NHE3 protein. cAMP, cGMP, and elevated Ca2+ due to apical exposure to UTP all inhibited NHE3 activity in wild-type mouse ileum but not in NHERF2-null mice, while inhibition by hyperosmolarity occurred normally. The cAMP-increased phosphorylation of NHE3 at aa 552; levels of PKAIIα and cGMP-dependent protein kinase II (cGKII); and elevation of Ca2+ were similar in wild-type and NHERF2-null mouse ileum. Luminal lysophosphatidic acid (LPA) stimulated NHE3 in wild-type but not in NHERF2-null ileum. In conclusion, 1) there are inftle structural abnormalities in the small intestine of NHERF2-null mouse which include fewer villus epithelial cells; 2) the decreased basal NHE3 activity and reduced brush border NHE3 amount in NHERF2-null mice show that NHERF2 is necessary for normal basal trafficking or retention of NHE3 in the apical domain; 3) hyperosmolar inhibition of NHE3 occurs similarly in wild-type and NHERF2-null ileum, demonstrating that some inhibitory mechanisms of NHE3 are not NHERF2 dependent; 4) cAMP inhibition of NHE3 is NHERF2 dependent at a step downstream of cAMP/PKAII phosphorylation of NHE3 at aa 552; 5) cGMP- and UTP-induced inhibition of NHE3 are NHERF2 dependent at steps beyond cGKII and the UTP-induced increase of intracellular Ca2+; and 6) LPA stimulation of NHE3 is also NHERF2 dependent.

Original languageEnglish (US)
Pages (from-to)C126-C136
JournalAmerican Journal of Physiology - Cell Physiology
Volume301
Issue number1
DOIs
StatePublished - Jul 2011

Keywords

  • 5'-cyclic monophosphate
  • Adenosine 3'
  • Ca
  • Guanosine 3'
  • Lysophosphatidic acid
  • Na/H exchanger regulation
  • Na/H exchanger regulatory factor
  • Trafficking

ASJC Scopus subject areas

  • Physiology
  • Cell Biology

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