Novel hexad repeats conserved in a putative transporter with restricted expression in cell types associated with growth, calcium exchange and homeostasis.
A transport protein is described with 12 transmembrane spans. Within the cytoplasmic amino-terminal domain, several novel hexad repeats are conserved in human, mouse, rat and pig, four to six of which had the canonical form PS_S_H(+). In the carboxyl-terminal domain, a polyglutamate sequence (5-8) is conserved. Restricted expression of the transporter was identified in acidophil cells of the adult pituitary that secrete growth hormone and prolactin. In the fetus, expression was restricted to osteoclasts, chondrocytes, thyroid, pituitary, central nervous system, eye, liver and heart. In particular, expression was found in structures associated with rapid calcium exchange including the retina, cardiomyocytes and in the intraplacental yolk sac that expresses calcitropic molecules. Furthermore, expression found in osteoclasts and kidney, within the distal portions of nephrons and collecting ducts, was consistent with a role in calcium homeostasis. In human pituitary, four mRNA transcripts, and in mouse kidney, three mRNA transcripts were expressed. In developing mouse kidney, the amount of each transcript varied that suggested the multiple transcripts might be differentially expressed in different physiological states. We propose that the transporter is specific for a calcium-chelator complex and is important for growth and calcium metabolism.
Brasier
Geoffrey
G
Department of Medicine, University of Melbourne, Parkville, Victoria, Australia.
Tikellis
Christos
C
Xuereb
Loredanna
L
Craigie
Jillian
J
Casley
David
D
Kovacs
Christopher S
CS
Fudge
Neva J
NJ
Kalnins
Renate
R
Cooper
Mark E
ME
Wookey
Peter J
PJ
D000595:Amino Acid Sequence; D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism*; D002455:Cell Division; D017124:Conserved Sequence; D005260:Female; D006706:Homeostasis; D006801:Humans; D007668:Kidney / Q000737:chemistry / Q000196:embryology; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D010902:Pituitary Gland / Q000737:chemistry / Q000166:cytology / Q000378:metabolism; D010920:Placenta / Q000737:chemistry; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution
D026901:Membrane Transport Proteins; D012333:RNA, Messenger; D002118:Calcium