Analysis of different complexes of type IIa sodium-dependent phosphate transporter in rat renal cortex using blue-native polyacrylamide gel electrophoresis

Type IIa sodium-dependent phosphate transporter (NaPi-IIa) can be localized
in the apical plasma membrane of renal proximal tubule to carry out a rate-limiting step
of phosphate reabsorption. For the apical localization, NaPi-IIa is required to form a
macromolecular complex with some adaptor proteins such as Na+/H+ exchanger regulatory
factor 1 (NHERF-1) and ezrin. However, the detail of macromolecular complex containing
NaPi-IIa in the apical membrane of the renal proximal tubular cells has not been
clarified. In this study, we identified at least four different complexes (220, 480, 920, 1,100
kDa) containing NaPi-IIa by using blue-native polyacrylamide gel electrophoresis. Interestingly,
LC-MS/MS analysis and immunoprecipitation analysis reveal that megalin
is a component of larger complexs (920 and 1,100 kDa). In addition, NaPi-IIa can be heterogeneously
co-localized with ezrin and megalin on the apical membrane of renal proximal
tubuler cells by fluorescence microscopy analysis. These results suggest that NaPi-IIa
can form some different complexes on the apical plasma membrane of renal proximal tubular
cells.

The journal of medical investigation : http://medical.med.tokushima-u.ac.jp/jmi/index.html