Binding and Cyclic AMP Stimulation by N-Terminally Deleted Human PTHs (3–84 and 4–84) in a Homologous Ligand Receptor System

Abstract

ABSTRACT

Sox-4 Messenger RNA Is Expressed in the Embryonic Growth Plate and Regulated via the Parathyroid Hormone/Parathyroid Hormone-Related Protein Receptor in Osteoblast-like Cells

“…The effects of PTH on Sox‐4 mRNA expression in osteoblastic cells are coupled via specific receptors. The dose‐dependent increase of Sox‐4 mRNA in OHS cells in response to PTH parallels the PTH‐stimulated cAMP production in human OHS cells and LLC‐PK 1 cells stably transfected with the cloned human PTH/PTHrP receptor, with effective concentrations with half maximal effect (EC 50 ) values of 2 × 10 −9 M (unpublished results) and 5 × 10 −10 M, respectively (28,47) . These results, together with the observation that PTH(3‐84) was unable to stimulate cAMP production, make the classical PTH/PTHrP receptor a strong candidate for mediating the stimulatory effect of PTH on Sox‐4 mRNA expression.…”

“…An intact N terminus of PTH is required for its stimulatory effect on Sox‐4 mRNA expression in OHS cells as shown by the equipotent ability of PTH(1‐84) and PTH(1‐34) to increase levels of Sox‐4, whereas the N‐terminally truncated form PTH(3‐84) had no effect. PTH(3‐84) is able to bind to the receptor but unable to stimulate cyclic monophosphate (cAMP) production (28) . Furthermore, Sox‐4 mRNA expression in OHS cells increased 3‐fold when the OHS cells were treated with the cAMP analog 8‐Br‐cAMP, but not with phorbol‐12‐myristate‐13‐acetate (TPA; not shown).…”

“…Commercial premade blots were from Clontech (Palo Alto, CA, U.S.A.). Recombinant hPTH(1‐84) and hPTH(3‐84) were prepared in our laboratory as described (28,29) . hPTH(1‐34) was purchased from Sigma (St. Louis, MO, U.S.A.); ExpressHyb and Marathon‐Ready cDNA were from Clontech; the OHS, KPDXM, and KRIB cell lines were obtained from Dr. Ø. Bruland (The Norwegian Radium Hospital, Oslo, Norway).…”

Dual Signaling and Ligand Selectivity of the Human PTH/PTHrP Receptor

“…(1)(2)(3)(4)(5)(6)(7)(8) The links between these individual signaling events and integrated tissue responses to PTH, such as the complex divergent effects of continuously versus intermittently administered exogenous PTH on net bone mass in vivo, (9) have not been clearly defined. Much effort has focused upon attempts to modulate PTHR signaling through use of PTH analogs, such as PTH or PTH , which may selectively activate one or the other of the two major PTHR signaling effectors, AC and PLC (10)(11)(12)(13)(14)(15)(16) For example, selective activation of the AC/protein kinase A (PKA) pathway by intermittently administered PTH(1-31), a putative ACselective PTHR agonist, was reported to account entirely for the anabolic response of bone in vivo, whereas hPTH(3-34), which does not activate AC but does stimulate protein kinase C (PKC) in bone cells, was inactive in vivo. (14,(16)(17)(18) Others have employed PTH to probe the involve-ment of PKC in the regulation of renal ion transporters and enzymes by PTH in rat and opposum kidney cells.…”