The protein phosphatase calcineurin determines basal parathyroid hormone gene expression.
Calcium and phosphate regulate PTH mRNA stability through differences in binding of parathyroid (PT) proteins to a minimal 63-nucleotide (nt) cis-acting instability element in its 3'-untranslated region. One of these proteins is adenosine-uridine-rich binding factor (AUF1), whose levels are not regulated in PT extracts from rats fed the different diets. However, two-dimensional gels showed posttranslational modification of AUF1 that included phosphorylation. There is no PT cell line, but in HEK 293 cells the 63-nt element is recognized as an instability element, and RNA interference for AUF1 decreased human PTH secretion in cotransfection experiments. Stably transfected cells with a chimeric GH gene containing the PTH 63-nt cis-acting element were used to study the signal transduction pathway that regulates AUF1 modification and chimeric gene mRNA stability. Cyclosporine A, the calcineurin inhibitor, regulated AUF1 posttranslationally, and this correlated with an increase in the stability of GH-PTH 63-nt mRNA but not of the control GH mRNA. Mice with genetic deletion of the calcineurin Abeta gene had markedly increased PTH mRNA levels that were still regulated by low calcium and phosphorus diets. Therefore, calcineurin regulates AUF1 posttranslationally in vitro and PTH gene expression in vivo but still allows its physiological regulation by calcium and phosphate.
Bell
Osnat
O
Minerva Center for Calcium and Bone Metabolism, Nephrology Services, Hadassah Hospital, PO Box 12000, Jerusalem 91120, Israel.
Gaberman
Elena
E
Kilav
Rachel
R
Levi
Ronen
R
Cox
Keith B
KB
Molkentin
Jeffery D
JD
Silver
Justin
J
Naveh-Many
Tally
T
D020413:3' Untranslated Regions; D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D019703:Calcineurin / Q000378:metabolism / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D016572:Cyclosporine / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D017353:Gene Deletion; D005786:Gene Expression Regulation; D000081035:Heterogeneous Nuclear Ribonucleoprotein D0; D034502:Heterogeneous-Nuclear Ribonucleoprotein D / Q000378:metabolism*; D006801:Humans; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D010281:Parathyroid Hormone / Q000096:biosynthesis* / Q000235:genetics; D010710:Phosphates / Q000378:metabolism; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D012313:RNA / Q000378:metabolism; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction; D014162:Transfection
D020413:3' Untranslated Regions; C000630986:HNRNPD protein, human; D000081035:Heterogeneous Nuclear Ribonucleoprotein D0; D034502:Heterogeneous-Nuclear Ribonucleoprotein D; C000630988:Hnrnpd protein, rat; C000630987:Hnrpd protein, mouse; D010281:Parathyroid Hormone; D010710:Phosphates; D012333:RNA, Messenger; D012313:RNA; D016572:Cyclosporine; D019703:Calcineurin; D002118:Calcium