Identification of molecular phenotypes and biased signaling induced by naturally occurring mutations of the human calcium-sensing receptor.
More than 200 naturally occurring mutations have been identified in the human CaSR, which have been linked to diseases involving dysregulation of extracellular Ca(2+) homeostasis. These mutations have classically been termed "loss-" or "gain-of-function" mutations, which is an oversimplification given that amino acid changes can alter numerous molecular properties of a receptor. We thus sought to characterize the effects of 21 clinically relevant mutations, the majority located in the heptahelical domains and extracellular loop regions of the CaSR, using flow cytometry to measure cell surface receptor expression levels, and measurements of intracellular Ca(2+) mobilization and ERK1/2 phosphorylation to monitor receptor signaling. We identified distinct molecular phenotypes caused by these naturally occurring amino acid substitutions, which included combinations of loss- and gain-of-expression and changes in intrinsic signaling capacity. Importantly, we also identified biased signaling in the response of the CaSR to different mutations across the two pathways, indicating that some mutations resulted in receptor conformations that differentially altered receptor-coupling preferences. These findings have important implications for understanding the causes of diseases linked to the CaSR. A full appreciation of the molecular effects of these amino acid changes may enable the development of therapeutics that specifically target the molecular determinant of impairment in the receptor.
Monash Institute of Pharmaceutical Sciences, 399 Royal Parade, Parkville, 3052, Victoria, Australia. katie.leach@monash.edu
Katie
K
Leach
Adriel
A
Wen
Anna E
AE
Davey
Patrick M
PM
Sexton
Arthur D
AD
Conigrave
Arthur
A
Christopoulos
D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D005434:Flow Cytometry; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000235:genetics / Q000378:metabolism; D009154:Mutation / Q000235:genetics*; D010766:Phosphorylation / Q000235:genetics / Q000502:physiology; D044169:Receptors, Calcium-Sensing / Q000235:genetics* / Q000502:physiology*
D007295:Inositol Phosphates; D044169:Receptors, Calcium-Sensing; C535150:MAPK1 protein, human; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D002118:Calcium