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Déliot, N; Hernando, N; Horst-Liu, Z; Gisler, S M; Capuano, P; Wagner, C A; Bacic, D; O'Brien, S; Biber, J; Murer, H (2005). Parathyroid hormone treatment induces dissociation of type IIa Na+-P(i) cotransporter-Na+/H+ exchanger regulatory factor-1 complexes. American Journal of Physiology: Cell Physiology, 289(1):C159-C167.

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Abstract

The type IIa Na+-P(i) cotransporter (NaP(i)-IIa) and the Na+/H+ exchanger regulatory factor-1 (NHERF1) colocalize in the apical membrane of proximal tubular cells. Both proteins interact in vitro. Herein the interaction between NaP(i)-IIa and NHERF1 is further documented on the basis of coimmunoprecipitation and co-pull-down assays. NaP(i)-IIa is endocytosed and degraded in lysosomes upon parathyroid hormone (PTH) treatment. To investigate the effect of PTH on the NaP(i)-IIa-NHERF1 association, we first compared the localization of both proteins after PTH treatment. In mouse proximal tubules and OK cells, NaP(i)-IIa was removed from the apical membrane after hormonal treatment; however, NHERF1 remained at the membrane. Moreover, PTH treatment led to degradation of NaP(i)-IIa without changes in the amount of NHERF1. The effect of PTH on the NaP(i)-IIa-NHERF1 interaction was further studied using coimmunoprecipitation. PTH treatment reduced the amount of NaP(i)-IIa coimmunoprecipitated with NHERF antibodies. PTH-induced internalization of NaP(i)-IIa requires PKA and PKC; therefore, we next analyzed whether PTH induces changes in the phosphorylation state of either partner. NHERF1 was constitutively phosphorylated. Moreover, in mouse kidney slices, PTH induced an increase in NHERF1 phosphorylation; independent activation of PKA or PKC also resulted in increased phosphorylation of NHERF1 in kidney slices. However, NaP(i)-IIa was not phosphorylated either basally or after exposure to PTH. Our study supports an interaction between NHERF1 and NaP(i)-IIa on the basis of their brush-border membrane colocalization and in vitro coimmunoprecipitation/co-pull-down assays. Furthermore, PTH weakens this interaction as evidenced by different in situ and in vivo behavior. The PTH effect takes place in the presence of increased phosphorylation of NHERF1.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Institute of Physiology
07 Faculty of Science > Institute of Physiology
DDC:570 Life sciences; biology
Language:English
Date:1 July 2005
Deposited On:11 Feb 2008 12:23
Last Modified:27 Nov 2013 19:45
Publisher:American Physiological Society
ISSN:0363-6143
Publisher DOI:10.1152/ajpcell.00456.2004
PubMed ID:15788483

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