Identification of a new gene product (diphor-1) regulated by dietary phosphate.
Chronic restriction of dietary Pi elicits an increased reabsorption of Pi in the kidney proximal tubules, which involves a stimulation of apical Na-Pi cotransport. This adaptation is in part a direct cellular response of which the mechanism(s) are poorly understood. In this study, the impact of dietary Pi restriction on the differential expression of rat kidney cortex mRNAs was visualized to identify gene products regulated by the Pi status. When kidney cortex mRNAs of rats fed a low- or a high-Pi diet were compared by differential display-polymerase chain reaction (DD-PCR), thirty modulated cDNA bands were observed, of which four were confirmed as being regulated. We focused on one of the upregulated bands, dietary Pi-regulated RNA-1 (diphor-1). A cDNA containing an open reading frame encoding a 52-kDa protein was cloned by library screening. Diphor-1 exhibits a high degree of identity to the Na/H exchanger regulatory factor and to a tyrosine kinase activating protein. Highest expression of diphor-1 mRNA was detected in the kidney (proximal tubules) and in small intestine. Expression experiments showed that diphor-1 specifically increases Na-Pi cotransport in oocytes of Xenopus laevis coinjected with renal type II Na-Pi contransporter cRNA. Further characterizations of diphor-1 will show whether diphor-1 is primarily or secondarily involved in the response to dietary Pi.
Custer
M
M
Institute of Physiology, University of Zurich, Switzerland.
Spindler
B
B
Verrey
F
F
Murer
H
H
Biber
J
J
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000502:physiology; D019976:Cloning, Organism; D003598:Cytoskeletal Proteins; D017931:DNA Primers; D004032:Diet; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects*; D007421:Intestine, Small / Q000378:metabolism; D007672:Kidney Cortex / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D008297:Male; D008861:Microsomes / Q000378:metabolism; D008969:Molecular Sequence Data; D009865:Oocytes / Q000502:physiology; D010710:Phosphates / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012964:Sodium / Q000378:metabolism; D050608:Sodium-Phosphate Cotransporter Proteins; D050610:Sodium-Phosphate Cotransporter Proteins, Type II; D027981:Symporters; D014158:Transcription, Genetic; D014981:Xenopus
D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D017931:DNA Primers; C109245:Pdzk1 protein, rat; D010710:Phosphates; D012333:RNA, Messenger; D011994:Recombinant Proteins; D050608:Sodium-Phosphate Cotransporter Proteins; D050610:Sodium-Phosphate Cotransporter Proteins, Type II; D027981:Symporters; D012964:Sodium