Cloning and functional expression of a Na(+)-dependent phosphate co-transporter from human kidney: cDNA cloning and functional expression

• Published in: Biochemical journal Vol. 305 ( Pt 1); no. 1; pp. 81 - 85
• Main Authors: Miyamoto, K, Tatsumi, S, Sonoda, T, Yamamoto, H, Minami, H, Taketani, Y, Takeda, E
• Format: Journal Article
• Language: English
• Published: England 01-01-1995
• Subjects: Animals; Base Sequence; Blotting, Northern; Carrier Proteins - genetics; Carrier Proteins - physiology; Cloning, Molecular; DNA, Complementary - genetics; DNA, Complementary - isolation & purification; DNA, Complementary - physiology; Female; Genomic Library; Humans; Kidney Cortex - chemistry; Kidney Cortex - physiology; Kinetics; Molecular Sequence Data; Oligonucleotides, Antisense - pharmacology; Phosphates - pharmacokinetics; Polymerase Chain Reaction; Rabbits; RNA, Complementary - analysis; RNA, Complementary - genetics; RNA, Messenger - analysis; RNA, Messenger - drug effects; RNA, Messenger - genetics; Sodium - pharmacokinetics; Sodium - pharmacology; Sodium-Phosphate Cotransporter Proteins; Sodium-Phosphate Cotransporter Proteins, Type I; Symporters; Xenopus laevis
• ISSN: 0264-6021; 1470-8728
• DOI: 10.1042/bj3050081

A cDNA clone encoding a protein 69% identical in amino acid sequence with that of the Na/P(i) co-transporter NaP(i)-1 was isolated from a human kidney cDNA library. The DNA sequence was identical with that of NPT-1 cDNA published by Chong, Kristjansson, Zoghbi and Hughe (1993) (Genomics, 18, 355-359). In the present study, we have characterized the function of the encoded protein and the tissue distribution of its mRNA. Injection of RNA transcribed from NPT-1 into Xenopus oocytes resulted in expression of Na/P(i) co-transport activity showing a high affinity for P(i) transport (Km 0.29 mM). Kinetic characterization ([P(i)], [Na+]) demonstrated that the expressed transport activity has properties similar to those displayed by oocytes injected with human kidney poly(A)+ RNA. Northern blotting demonstrated that NPT-1 mRNA is expressed in renal cortex, liver and brain but not in other tissues. Hybrid depletion with antisense oligonucleotides to NaP(i)-3 and NPT-1 completely inhibited poly(A)+ RNA-induced Na(+)-dependent P(i) uptake in oocytes. These findings indicate that two high-affinity Na/P(i) cotransporters (NaP(i)-3 and NPT-1) are present in human kidney cortex.