GABARAP deficiency modulates expression of NaPi-IIa in renal brush-border membranes

Sonja C. Reining, Serge M. Gisler, Daniel Fuster, Orson W. Moe, Gregory A. O'Sullivan, Heinrich Betz, Jürg Biber, Heini Murer, Nati Hernando

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

Renal reabsorption of inorganic phosphate (Pi) is mainly mediated by the Na+-dependent Pi-cotransporter NaPi-IIa that is expressed in the brush-border membrane (BBM) of renal proximal tubules. Regulation and apical expression of NaPi-IIa are known to depend on a network of interacting proteins. Most of the interacting partners identified so far associate with the COOH-terminal PDZ-binding motif (TRL) of NaPi-IIa. In this study GABAA receptor-associated protein (GABARAP) was identified as a novel interacting partner of NaPi-IIa applying a membrane yeast-two-hybrid system (MYTH 2.0) to screen a mouse kidney library with the TRL-truncated cotransporter as bait. GABARAP mRNA and protein are present in renal tubules, and the interaction of NaPi-IIa and GABARAP was confirmed by using glutathione S-transferase pulldowns from BBM and coimmunoprecipitations from transfected HEK293 cells. Amino acids 36-68 of GABARAP were identified as the determinant for the described interaction. The in vivo effects of this interaction were studied in a murine model. GABARAP-/- mice have reduced urinary excretion of Pi, higher Na+-dependent 32P i uptake in BBM vesicles, and increased expression of NaPi-IIa in renal BBM compared with GABARAP+/+ mice. The expression of Na +/H+ exchanger regulatory factor (NHERF)1, an important scaffold for the apical expression of NaPi-IIa, is also increased in GABARAP-/- mice. The absence of GABARAP does not interfere with the regulation of the cotransporter by either parathyroid hormone or acute changes of dietary Pi content.

Original languageEnglish (US)
Pages (from-to)F1118-F1128
JournalAmerican Journal of Physiology - Renal Physiology
Volume296
Issue number5
DOIs
StatePublished - May 2009

Keywords

  • Epithelial transport
  • Phosphate homeostasis
  • Renal proximal tubules

ASJC Scopus subject areas

  • Physiology
  • Urology

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