Luminal and contraluminal stop-flow microperfusion was applied, and the apparent Ki values (mmol/l) against the luminal phosphate and the contraluminal p-aminohippurate (PAH), sulfate and dicarboxylate transport systems were evaluated. Luminal phosphate transporter: Among the 20 compounds tested only phosphonoformate (foscarnet), etidronate, and clodronate have a good affinity (app.Ki < 1 mmol/...

Secondary active transport of substrate across the cell membrane is crucial to many cellular and physiological processes. The crystal structure of one member of the secondary active transporter family, the sn-glycerol-3-phosphate (G3P) transporter (GlpT) of the inner membrane of Escherichia coli, suggests a mechanism for substrate translocation across the membrane that involves a rocker-switch-...

Plant vacuoles serve as the primary intracellular compartments for inorganic phosphate (Pi) storage. Passage of Pi across vacuolar membranes plays a critical role in buffering the cytoplasmic Pi level against fluctuations of external Pi and metabolic activities. Here we demonstrate that the SPX-MFS proteins, designated as PHOSPHATE TRANSPORTER 5 family (PHT5), also named Vacuolar Phosphate Tran...

The prevention of phosphate retention in chronic renal disease may reduce both renal osteodystrophy and disease progression. We evaluated the expression of the sodium-dependent phosphate transporter, NaPi-2, and the response to phosphonoformic acid (PFA) in rats with 5/6 nephrectomy-induced renal failure. Partial nephrectomy resulted in a significant proteinuria and reduced renal function. In a...

BACKGROUND The mammalian target of rapamycin (mTOR) is known to stimulate a variety of transport mechanisms including the intestinal phosphate transporter NaPi-IIb. The present study was performed to elucidate whether mTOR similarly regulates the major renal tubular phosphate transporter NaPi-IIa. METHODS To this end, NaPi-IIa was expressed in Xenopus oocytes with or without mTOR and phosphat...

Using a high-affinity phosphate transporter gene of Arabidopsis thaliana, PHT1, as a probe, three Arabidopsis homologs were isolated, named PHT4, PHT5 and PHT6, in addition to the previously isolated PHT2 and PHT3. The amino acid sequences deduced from the three nucleotides were 32-42% homologous with microbial phosphate transporters of Saccharomyces cerevisiae (PHO84), Neurospora crassa (PHO-5...

The sodium-dependent renal phosphate transporter (Npt2, Na-Pi IIa) is the major regulated phosphate transporter in the renal proximal convoluted tubule. Npt2 associates with a number of PDZ-containing proteins including Na+H+ exchanger regulatory factor-1 (NHERF-1). To determine whether NHERF-1 is involved in the acute regulation of phosphate transport, wild-type and NHERF-1 (-/-) mice were sta...

Renal phosphate excretion and serum level are critically determined by several sodium-dependent phosphate transporters expressed in the proximal tubule, among them NaPi-IIa and NaPi-IIc.1,2 In humans, mutations in NaPi-IIc (SLC34A3) cause hereditary hypophosphatemic rickets with hypercalciuria. In contrast, the role of NaPi-IIa (SLC34A1) in renal syndromes of hyperphosphaturia and nephrolithias...