title: Allosteric modulation of the calcium-sensing receptor by gamma-glutamyl peptides: inhibition of PTH secretion, suppression of intracellular cAMP levels, and a common mechanism of action with L-amino acids.
abstract: γ-Glutamyl peptides were identified previously as novel positive allosteric modulators of Ca(2+)(o)-dependent intracellular Ca(2+) mobilization in HEK-293 cells that bind in the calcium-sensing receptor VFT domain. In the current study, we investigated whether γ-glutamyl-tripeptides including γ-Glu-Cys-Gly (glutathione) and its analogs S-methylglutathione and S-propylglutathione, or dipeptides including γ-Glu-Ala and γ-Glu-Cys are positive allosteric modulators of Ca(2+)(o)-dependent Ca(2+)(i) mobilization and PTH secretion from normal human parathyroid cells as well as Ca(2+)(o)-dependent suppression of intracellular cAMP levels in calcium-sensing receptor (CaR)-expressing HEK-293 cells. In addition, we compared the effects of the potent γ-glutamyl peptide S-methylglutathione, and the amino acid L-Phe on HEK-293 cells that stably expressed either the wild-type CaR or the double mutant T145A/S170T, which exhibits selectively impaired responses to L-amino acids. We find that γ-glutamyl peptides are potent positive allosteric modulators of the CaR that promote Ca(2+)(o)-dependent Ca(2+)(i) mobilization, suppress intracellular cAMP levels and inhibit PTH secretion from normal human parathyroid cells. Furthermore, we find that the double mutant T145A/S170T exhibits markedly impaired Ca(2+)(i) mobilization and cAMP suppression responses to S-methylglutathione as well as L-Phe indicating that γ-glutamyl peptides and L-amino acids activate the CaR via a common mechanism.
authors.affiliation: School of Molecular Bioscience, University of Sydney, New South Wales 2006, Australia.
authors.forename: Geoffrey K
authors.initials: GK
authors.lastname: Broadhead
authors.forename: Hee-chang
authors.initials: HC
authors.lastname: Mun
authors.forename: Vimesh A
authors.initials: VA
authors.lastname: Avlani
authors.forename: Orane
authors.initials: O
authors.lastname: Jourdon
authors.forename: W Bret
authors.initials: WB
authors.lastname: Church
authors.forename: Arthur
authors.initials: A
authors.lastname: Christopoulos
authors.forename: Leigh
authors.initials: L
authors.lastname: Delbridge
authors.forename: Arthur D
authors.initials: AD
authors.lastname: Conigrave
mesh_terms: D000596:Amino Acids / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D000242:Cyclic AMP / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D009154:Mutation; D009842:Oligopeptides / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D010281:Parathyroid Hormone / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D044169:Receptors, Calcium-Sensing / Q000235:genetics / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D009842:Oligopeptides; D010281:Parathyroid Hormone; D044169:Receptors, Calcium-Sensing; D000242:Cyclic AMP; D002118:Calcium