Prolonged calcitonin receptor signaling by salmon, but not human calcitonin, reveals ligand bias

• Published in: PloS one Vol. 9; no. 3; p. e92042
• Main Authors: Andreassen, Kim Vietz, Hjuler, Sara Toftegaard, Furness, Sebastian G, Sexton, Patrick M, Christopoulos, Arthur, Nosjean, Olivier, Karsdal, Morten Asser, Henriksen, Kim
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 18.03.2014; Public Library of Science (PLoS)
• Subjects: Activation; Analysis; Animals; Arrestin; Arrestins - genetics; Arrestins - metabolism; beta-Arrestins; Biology; Biology and Life Sciences; Calcitonin; Calcitonin - genetics; Calcitonin - metabolism; Cell Line; Cell lines; Cells (Biology); Computer and Information Sciences; Cyclic adenosine monophosphate; Cyclic AMP; Cyclic AMP - metabolism; Diabetes; Dose response profiles; Gene Expression Regulation; Humans; Internalization; Kinetics; Ligands; Peptides; Pharmaceutical sciences; Pharmacology; Protein Transport; Proteins; Receptors; Receptors, Calcitonin - genetics; Receptors, Calcitonin - metabolism; Recruitment; Rodents; Salmon; Signal transduction; Signal Transduction - genetics; Signaling; Species Specificity; Stimulation; Time Factors; Transgenes
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0092042

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.