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

Characterization of parathyroid hormone/parathyroid hormone-related protein receptor and signaling in hypercalcemic Walker 256 tumor cells

“…Therefore, we used this approach to determine whether the G q/11 protein was coupled to the PTHrP receptor in W256 tumor cell membranes. Current evidence suggests that PTHrP(1-34) and PTHrP(1-36) were equivalent in binding to PTHR and the subsequent activation of phospholipase C (Abu-Samra et al 1992, Schipani et al 1993, Takasu & Bringhurst 1998, Takasu et al 1999. We found that PTHrP(1-36), between 1 nM (Fig.…”

“…The N-terminal region of PTHrP exhibits structural homology with that of parathyroid hormone (PTH), which accounts for its binding to the common type I PTH/PTHrP receptor (PTHR), cloned in bone and kidney cells, with high affinity (Schipani et al 1993). In these cells, the PTHR signals via the phospholipase C and adenylate cyclase pathways through interaction with various G proteins , Takasu et al 1999. However, in HTLV-I-infected lymphocytes, in normal rat islet as well as rat insulinoma cells, and in squamous carcinoma cells, incompletely characterized PTHrP receptors show features different from those of PTHR, e.g.…”

Contributions of parathyroid hormone (PTH)/PTH-related peptide receptor signaling pathways to the anabolic effect of PTH on bone

“…In this regard, PKC signaling via PTH1Rs has been related to induction of osteoblastic bone formation [16,24], especially PKC stimulated by the PTH(29-34) portion of the ligand [14,21]. G 1 ,R 19 (1-28) lacks the 29-34 domain of hPTH(1-34) required for PLC-independent PKC activation and incorporates a Ser 1 to Gly 1 mutation that blocks PLC activation (the Arg 19 change improves binding affinity that otherwise is compromised by the C-terminal truncation) [27]. This peptide can no longer activate PKC via either PLC-dependent or PLC-independent mechanisms but can fully activate cAMP production via PTH1Rs, albeit with somewhat reduced potency [26,31].…”

“…Thus, the first two amino-terminal residues of hPTH(1-34) (Ser 1 -Val 2 ) are known to be required for activation of adenylyl cylcase, and use of amino-truncated analogs such as PTH(2-34), PTH or desamino-hPTH(1-34) (Npropionyl (2-3)hPTH-amide) in vivo has failed to elicit a full anabolic response, leading to the conclusion that cAMP is responsible for mediating the anabolic response to PTH [11,22]. Further, carboxyl-terminal truncation, to remove the sequence His 32 -Asn 33 -Phe 34 (i.e., hPTH ), precludes activation of membrane-associated PKC(s) but does not impair stimulation of adenylyl cyclase or eliminate the anabolic response in vivo, which has further supported the role of cAMP in the anabolic response [13,22,26,27]. Other evidence suggests that PTH1R-dependent adenylyl cyclase activation alone may not be sufficient to elicit a full anabolic response, however [18,19], and interpretation of the studies with amino-truncated analogs was clouded by the lack of recognition that the PLC/PKC response to PTH is critically dependent upon the presence of the α-amino group of the amino-terminal Ser 1 of hPTH(1-34) -i.e., inactive amino-truncated fragments actually lack both adenylyl cyclase and PLC/PKC responses [26].…”

“…Previous work from our group has demonstrated that substitution of glycine for the native serine at position 1 of hPTH(1-34) dramatically impairs PLC activation without eliminating cAMP generation and, as well, allows for retention of PLC-independent PKC activation as long as the 29-34 domain is present [27,31]. In the present experiments, we employed two signaling-selective peptides, [Gly 1 , Arg 19 ]hPTH and [Gly 1 ,Arg 19 ]hPTH(1-34), together with PTH(1-34), to investigate, in vivo, the anabolic effects of different signaling pathways generated by PTH and to test the hypothesis that PTH1R-generated PKC signaling, arising via either PLC-dependent or PLC-independent mechanisms, contributes to the anabolic response of bone.…”