Parathyroid hormone treatment induces dissociation of type IIa Na + -P i cotransporter-Na + /H + exchanger regulatory factor-1 complexes
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 coimmuno...
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Published in | American Journal of Physiology: Cell Physiology Vol. 289; no. 1; pp. C159 - C167 |
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Main Authors | , , , , , , , , , |
Format | Journal Article |
Language | English |
Published |
American Physiological Society
01.07.2005
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Subjects | |
Online Access | Get full text |
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Summary: | 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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ISSN: | 0363-6143 1522-1563 |
DOI: | 10.1152/ajpcell.00456.2004 |