title: Extracellular calcium sensing receptor stimulation in human colonic epithelial cells induces intracellular calcium oscillations and proliferation inhibition.
abstract: The extracellular Ca(2+)-sensing receptor (CaR) is increasingly implicated in the regulation of multiple cellular functions in the gastrointestinal tract, including secretion, proliferation and differentiation of intestinal epithelial cells. However, the signaling mechanisms involved remain poorly defined. Here we examined signaling pathways activated by the CaR, including Ca(2+) oscillations, in individual human colon epithelial cells. Single cell imaging of colon-derived cells expressing the CaR, including SW-480, HT-29, and NCM-460 cells, shows that stimulation of this receptor by addition of aromatic amino acids or by an elevation of the extracellular Ca(2+) concentration promoted striking intracellular Ca(2+) oscillations. The intracellular calcium oscillations in response to extracellular Ca(2+) were of sinusoidal pattern and mediated by the phospholipase C/diacylglycerol/inositol 1,4,5-trisphosphate pathway as revealed by a biosensor that detects the accumulation of diacylglycerol in the plasma membrane. The intracellular calcium oscillations in response to aromatic amino acids were of transient type, that is, Ca(2+) spikes that returned to baseline levels, and required an intact actin cytoskeleton, a functional Rho, Filamin A and the ion channel TRPC1. Further analysis showed that re-expression and stimulation of the CaR in human epithelial cells derived from normal colon and from colorectal adenocarcinoma inhibits their proliferation. This inhibition was associated with the activation of the signaling pathway that mediates the generation of sinusoidal, but not transient, intracellular Ca(2+) oscillations. Thus, these results indicate that the CaR can function in two signaling modes in human colonic epithelial cells offering a potential link between gastrointestinal responses and food/nutrients uptake and metabolism.
authors.affiliation: Unit of Signal Transduction and Gastrointestinal Cancer, Division of Digestive Diseases, Department of Medicine, CURE, Digestive Diseases Research Center, Molecular Biology Institute and Jonsson Comprehensive Cancer Center, David Geffen School of Medicine, University of California at Los Angeles, California 90095-1786, USA. orey@mednet.ucla.edu
authors.forename: Osvaldo
authors.initials: O
authors.lastname: Rey
authors.forename: Steven H
authors.initials: SH
authors.lastname: Young
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Jacamo
authors.forename: Mary P
authors.initials: MP
authors.lastname: Moyer
authors.forename: Enrique
authors.initials: E
authors.lastname: Rozengurt
mesh_terms: D000199:Actins / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology*; D002460:Cell Line; D049109:Cell Proliferation; D003106:Colon / Q000166:cytology*; D003285:Contractile Proteins / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology / Q000502:physiology*; D064448:Filamins; D006801:Humans; D008840:Microfilament Proteins / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D044169:Receptors, Calcium-Sensing / Q000235:genetics / Q000378:metabolism*; D050052:TRPC Cation Channels / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000378:metabolism
chemical_list: D000199:Actins; D003285:Contractile Proteins; D064448:Filamins; D008840:Microfilament Proteins; D012333:RNA, Messenger; D044169:Receptors, Calcium-Sensing; D050052:TRPC Cation Channels; C096351:transient receptor potential cation channel, subfamily C, member 1; D011493:Protein Kinase C; D020741:rho GTP-Binding Proteins; D002118:Calcium