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The type IIc [Na.sup.+]-dependent phosphate cotransporter (NaPi-IIc) is specifically targeted to, and expressed on, the apical membrane of renal proximal tubular cells and mediates phosphate transport. In the present study, we investigated the signals that determine apical expression of NaPi-IIc with a focus on the role of the N- and the C-terminal tails of mouse NaPi-IIc in renal epithelial cells [opossum kidney (OK) and Madin-Darby canine kidney cells]. Wild-type NaPi-IIc, the cotransporter NaPi-IIa, as well as several IIa-IIc chimeras and deletion mutants, were fused to enhanced green fluorescent protein (EGFP), and their cellular localization was analyzed in polarized renal epithelial cells by confocal microscopy and by cell-surface biotinylation. Fluorescent EGFP-fused NaPi-IIc transporter proteins are correctly expressed in the apical membrane of OK cells. The apical expression of N-terminal deletion mutants (deletion of N-terminal 25, 50, or 69 amino acids) was not affected by truncation. In contrast, C-terminal deletion mutants (deletion of C-terminal 45, 50, or 62 amino acids) did not have correct apical expression. A more detailed mutational analysis indicated that a domain (amino acids WLHSL) in the cytoplasmic C terminus is required for apical expression of NaPi-IIc in renal epithelial cells. We conclude that targeting of NaPi-IIc to the apical cell surface is regulated by a unique amino acid motif in the cytoplasmic C-terminal domain. Npt2c; SLC34A3; localization; OK cell; hereditary hypophosphatemic rickets with hypercalciuria doi: 10.1152/ajprenal.00189.2009.

During bone resorption, a large amount of inorganic phosphate ([P.sub.i]) is generated within the osteoclast hemivacuole. The mechanisms involved in the disposal of this [P.sub.i] are not clear. In the present study, we investigated the efflux of [P.sub.i] from osteoclast-like cells. [P.sub.i] efflux was activated by acidic conditions in osteoclast-like cells derived by the treatment of RAW264.7 cells with receptor activator of nuclear factor-[kappa]B ligand. Acid-induced [P.sub.i] influx was not observed in renal proximal tubule-like opossum kidney cells, osteoblast-like MC3T3-E1 cells, or untreated RAW264.7 cells. Furthermore, [P.sub.i] efflux was stimulated by extracellular [P.sub.i] and several [P.sub.i] analogs [phosphonoformic acid (PFA), phosphonoacetic acid, arsenate, and pyrophosphate]. [P.sub.i] efflux was time dependent, with 50% released into the medium after 10 min. The efflux of [P.sub.i] was increased by various inhibitors that block [P.sub.i] uptake, and extracellular [P.sub.i] did not affect the transport of [sup.14]C]PFA into the osteoclast-like cells. Preloading of cells with [P.sub.i] did not stimulate [P.sub.i] efflux by PFA, indicating that the effect of [P.sub.i] was not due to transstimulation of [P.sub.i] transport. [P.sub.i] uptake was also enhanced under acidic conditions. Agents that prevent increases in cytosolic free [Ca.sup.2+] concentration, including acetoxymethyl ester of 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid, 2-aminoethoxydiphenyl borate, and bongkrekic acid, significantly inhibited [P.sub.i] uptake in the osteoclast-like cells, suggesting that [P.sub.i] uptake is regulated by [Ca.sup.2+] signaling in the endoplasmic reticulum and mitochondria of osteoclast-like cells. These results suggest that osteoclast-like cells have a unique [P.sub.i] uptake/efflux system and can prevent [P.sub.i] accumulation within osteoclast hemivacuoles. phosphate transporter; RAW264.7; proton dependent; acidification

The type IIc Na+-dependent phosphate cotransporter (NaPi-IIc) is specifically targeted to, and expressed on, the apical membrane of renal proximal tubular cells and mediates phosphate transport. In the present study, we investigated the signals that determine apical expression of NaPi-IIc with a focus on the role of the N- and the C-terminal tails of mouse NaPi-IIc in renal epithelial cells [opossum kidney (OK) and Madin-Darby canine kidney cells]. Wild-type NaPi-IIc, the cotransporter NaPi-IIa, as well as several IIa-IIc chimeras and deletion mutants, were fused to enhanced green fluorescent protein (EGFP), and their cellular localization was analyzed in polarized renal epithelial cells by confocal microscopy and by cell-surface biotinylation. Fluorescent EGFP-fused NaPi-IIc transporter proteins are correctly expressed in the apical membrane of OK cells. The apical expression of N-terminal deletion mutants (deletion of N-terminal 25, 50, or 69 amino acids) was not affected by truncation. In contrast, C-terminal deletion mutants (deletion of C-terminal 45, 50, or 62 amino acids) did not have correct apical expression. A more detailed mutational analysis indicated that a domain (amino acids WLHSL) in the cytoplasmic C terminus is required for apical expression of NaPi-IIc in renal epithelial cells. We conclude that targeting of NaPi-IIc co the apical cell surface is regulated by a unique amino acid motif in the cytoplasmic C-terminal domain. [ABSTRACT FROM AUTHOR]

Provides information on a study which investigated the correlation of Glut-1 glucose transporter expression with ...F2-fluoro-2-deoxy-D-glucose uptake in non-small cell lung cancer. Materials and methods used in the study; Results and discussion.

It is widely accepted that green plants evolved the capacity to synthesize the highly organized branched alpha-polyglucan amylopectin with tandem-cluster structure, whereas animals and bacteria continued to produce random branched glycogen. Although most previous studies documented that cyanobacteria accumulate glycogen, the present study shows explicitly that some cyanobacteria such as Cyanobacterium sp. MBIC10216, Myxosarcina burmensis and Synechococcus sp. BG043511 had distinct alpha-polyglucans, which were designated as semi-amylopectin. The semi-amylopectin was intermediate between rice amylopectin and typical cyanobacterial glycogen in terms of chain length distribution, molecular size and length of the most abundant alpha-1,4-chain. It was also found that Cyanobacterium sp. MBIC10216 had no amylose-type component in its alpha-polyglucans. The evolutionary aspect of the structure of alpha-polyglucan is discussed in relation to the phylogenetic evolutionary tree of 16S rRNA sequences of cyanobacteria.