NDLI: Defective jejunal and colonic salt absorption and altered $Na^{+}/H^{+}$ exchanger 3 (NHE3) activity in NHE regulatory factor 1 (NHERF1) adaptor protein-deficient mice

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Broere, N. Chen, M. Cinar, A. Singh, A. K. Hillesheim, J. Riederer, B. Lünnemann, M. Rottinghaus, I. Krabbenhöft, A. Engelhardt, R. Rausch, B. Weinman, E. J. Donowitz, M. Hubbard, A. Kocher, O. de Jonge, H. R. Hogema, B. M. Seidler, U.
Description	Country affiliation: Netherlands Author Affiliation: Broere N ( Department of Biochemistry, Erasmus University Medical Center, Rotterdam, The Netherlands.)
Abstract	We investigated the role of the Na(+)/H(+) exchanger regulatory factor 1 (NHERF1) on intestinal salt and water absorption, brush border membrane (BBM) morphology, and on the NHE3 mRNA expression, protein abundance, and transport activity in the murine intestine. NHERF1-deficient mice displayed reduced jejunal fluid absorption in vivo, as well as an attenuated in vitro Na(+) absorption in isolated jejunal and colonic, but not of ileal, mucosa. However, cAMP-mediated inhibition of both parameters remained intact. Acid-activated NHE3 transport rate was reduced in surface colonocytes, while its inhibition by cAMP and cGMP was normal. Immunodetection of NHE3 revealed normal NHE3 localization in the BBM of NHERF1 null mice, but NHE3 abundance, as measured by Western blot, was significantly reduced in isolated BBM from the small and large intestines. Furthermore, the microvilli in the proximal colon, but not in the small intestine, were significantly shorter in NHERF1 null mice. Additional knockout of PDZK1 (NHERF3), another member of the NHERF family of adaptor proteins, which binds to both NHE3 and NHERF1, further reduced basal NHE3 activity and caused complete loss of cAMP-mediated NHE3 inhibition. An activator of the exchange protein activated by cAMP (EPAC) had no effect on jejunal fluid absorption in vivo, but slightly inhibited NHE3 activity in surface colonocytes in vitro. In conclusion, NHERF1 has segment-specific effects on intestinal salt absorption, NHE3 transport rates, and NHE3 membrane abundance without affecting mRNA levels. However, unlike PDZK1, NHERF1 is not required for NHE3 regulation by cyclic nucleotides.
File Format	HTM / HTML
ISSN	00316768
e-ISSN	14322013
DOI	10.1007/s00424-008-0579-1
Journal	Pflügers Archiv - European Journal of Physiology
Issue Number	5
Volume Number	457
Language	English
Publisher	Springer
Publisher Date	2009-03-01
Publisher Place	Germany
Access Restriction	Open
Subject Keyword	Discipline Physiology Colon Metabolism Intestinal Absorption Physiology Jejunum Phosphoproteins Deficiency Sodium Chloride Sodium-hydrogen Antiporter Animals Immunohistochemistry Intestinal Mucosa Mice Microvilli Ultrastructure Research Support, Non-u.s. Gov't
Content Type	Text
Resource Type	Article
Subject	Physiology Physiology (medical) Clinical Biochemistry

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