title: Prolonged calcitonin receptor signaling by salmon, but not human calcitonin, reveals ligand bias.
abstract: Salmon calcitonin (sCT) and human calcitonin (hCT) are pharmacologically distinct. However, the reason for the differences is unclear. Here we analyze the differences between sCT and hCT on the human calcitonin receptor (CT(a)R) with respect to activation of cAMP signaling, β-arrestin recruitment, ligand binding kinetics and internalization. The study was conducted using mammalian cell lines heterologously expressing the human CT(a) receptor. CT(a)R downstream signaling was investigated with dose response profiles for cAMP production and β-arrestin recruitment for sCT and hCT during short term (<2 hours) and prolonged (up to 72 hours) stimulation. CT(a)R kinetics and internalization was investigated with radio-labeled sCT and hCT ligands on cultured cells and isolated membrane preparations from the same cell line. We found that sCT and hCT are equipotent during short-term stimulations with differences manifesting themselves only during long-term stimulation with sCT inducing a prolonged activation up to 72 hours, while hCT loses activity markedly earlier. The prolonged sCT stimulation of both cAMP accumulation and β-arrestin recruitment was attenuated, but not abrogated by acid wash, suggesting a role for sCT activated internalized receptors. We have demonstrated a novel phenomenon, namely that two distinct CT(a)R downstream signaling activation patterns are activated by two related ligands, thereby highlighting qualitatively different signaling responses in vitro that could have implications for sCT use in vivo.
authors.affiliation: Nordic Bioscience A/S, Herlev, Denmark.
authors.forename: Kim Vietz
authors.initials: KV
authors.lastname: Andreassen
authors.affiliation: Nordic Bioscience A/S, Herlev, Denmark.
authors.forename: Sara Toftegaard
authors.initials: ST
authors.lastname: Hjuler
authors.affiliation: Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Victoria, Australia.
authors.forename: Sebastian G
authors.initials: SG
authors.lastname: Furness
authors.affiliation: Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Victoria, Australia.
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Sexton
authors.affiliation: Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Victoria, Australia.
authors.forename: Arthur
authors.initials: A
authors.lastname: Christopoulos
authors.affiliation: Institut de Recherches Servier, Croissy-sur-Seine, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Nosjean
authors.affiliation: Nordic Bioscience A/S, Herlev, Denmark.
authors.forename: Morten Asser
authors.initials: MA
authors.lastname: Karsdal
authors.affiliation: Nordic Bioscience A/S, Herlev, Denmark.
authors.forename: Kim
authors.initials: K
authors.lastname: Henriksen
mesh_terms: D000818:Animals; D019390:Arrestins / Q000235:genetics / Q000378:metabolism; D002116:Calcitonin / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D008024:Ligands; D021381:Protein Transport; D018003:Receptors, Calcitonin / Q000235:genetics / Q000378:metabolism*; D012474:Salmon; D015398:Signal Transduction / Q000235:genetics*; D013045:Species Specificity; D013997:Time Factors; D019076:Transgenes; D000071557:beta-Arrestins
chemical_list: D019390:Arrestins; D008024:Ligands; D018003:Receptors, Calcitonin; D000071557:beta-Arrestins; C028815:salmon calcitonin; D002116:Calcitonin; D000242:Cyclic AMP