Structurally diverse N-terminal peptides of parathyroid hormone (PTH) and PTH-related peptide (PTHRP) inhibit the Na+/H+ exchanger NHE3 isoform by binding to the PTH/PTHRP receptor type I and activating distinct signaling pathways

J Biol Chem. 1996 Jun 21;271(25):14931-6. doi: 10.1074/jbc.271.25.14931.


N-terminal peptides of parathyroid hormone (PTH) and PTH-related peptide (PTHRP) elicit a wide variety of biological responses in target cells, including the inhibition of Na+/H+ exchanger NHE3 activity in renal cells. This response is believed to be mediated by ligand binding to a common receptor (i.e. PTH/PTHRP receptor type I) and activation of cAMP-dependent and/or Ca2+/phospholipid-dependent protein kinases (PKA and PKC, respectively). However, the mechanism of action of these N-terminal peptides is now unclear because of recent data reporting the existence of additional receptor isoforms. Therefore, to directly examine the ligand binding and signaling characteristics of the PTH/PTHRP receptor type I and its ability to elicit a biological response, cDNAs encoding the rat type I receptor and the rat NHE3 isoform were transfected into Chinese hamster ovary (AP-1) cells that lack endogenous expression of these proteins. Competition binding assays using [125I-Tyr36]PTHRP-(1-36)-NH2 radioligand indicated that several biologically active human N-terminal PTH and PTHRP fragments (PTH-(1-34), PTH-(3-34), PTH-(28-42), PTH-(28-48), and PTHRP-(1-34)) were capable of binding to the type I receptor. Both PTH-(1-34) and PTHRP-(1-34) stimulated adenylate cyclase and PKC activities in these cells, whereas PTH-(3-34), PTH-(28-42), and PTH-(28-48) selectively enhanced only PKC activity. PTHRP-(1-16), a biologically inert fragment, was incapable of binding to this receptor and influencing either the PKA or PKC pathway. Furthermore, all the analogues with the exception of PTHRP-(1-16) inhibited NHE3 activity. Inhibition of PKC by the potent antagonist chelerythrine chloride abolished the depression of NHE3 activity by PTH-(3-34), PTH-(28-42), and PTH-(28-48) but did not alleviate the effects of PTH-(1-34). Likewise, antagonism of PKA by H-89 was unable to prevent the inhibition caused by PTH-(1-34). However, inhibition of both PKA and PKC by the nonselective protein kinase antagonist H-7 abolished the reduction of NHE3 activity by PTH-(1-34). These data indicate that discrete N-terminal analogues of PTH and PTHRP can interact with the classical PTH/PTHRP receptor type I and activate PKA and/or PKC. Activation of either signaling pathway independently leads to inhibition of NHE3.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine
  • Animals
  • Binding, Competitive
  • CHO Cells
  • Cricetinae
  • Cyclic AMP-Dependent Protein Kinases / metabolism
  • Enzyme Inhibitors / pharmacology
  • Humans
  • Isoquinolines / pharmacology
  • Kinetics
  • Parathyroid Hormone / metabolism
  • Parathyroid Hormone / pharmacology*
  • Parathyroid Hormone-Related Protein
  • Peptide Fragments / metabolism
  • Peptide Fragments / pharmacology*
  • Piperazines / pharmacology
  • Protein Kinase C / metabolism
  • Protein Kinase Inhibitors
  • Proteins / metabolism
  • Proteins / pharmacology*
  • Rats
  • Receptors, Parathyroid Hormone / biosynthesis
  • Receptors, Parathyroid Hormone / physiology*
  • Recombinant Proteins / antagonists & inhibitors
  • Recombinant Proteins / biosynthesis
  • Signal Transduction / drug effects*
  • Sodium-Hydrogen Exchanger 3
  • Sodium-Hydrogen Exchangers / antagonists & inhibitors*
  • Sodium-Hydrogen Exchangers / biosynthesis
  • Structure-Activity Relationship
  • Transfection


  • Enzyme Inhibitors
  • Isoquinolines
  • PTHLH protein, human
  • Parathyroid Hormone
  • Parathyroid Hormone-Related Protein
  • Peptide Fragments
  • Piperazines
  • Protein Kinase Inhibitors
  • Proteins
  • Receptors, Parathyroid Hormone
  • Recombinant Proteins
  • SLC9A3 protein, human
  • Slc9a3 protein, rat
  • Sodium-Hydrogen Exchanger 3
  • Sodium-Hydrogen Exchangers
  • 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine
  • Cyclic AMP-Dependent Protein Kinases
  • Protein Kinase C