The extracellular calcium-sensing receptor is required for cholecystokinin secretion in response to l-phenylalanine in acutely isolated intestinal I cells
- 1 April 2011
- journal article
- research article
- Published by American Physiological Society in American Journal of Physiology-Gastrointestinal and Liver Physiology
- Vol. 300 (4), G538-G546
- https://doi.org/10.1152/ajpgi.00342.2010
Abstract
The extracellular calcium-sensing receptor (CaSR) has recently been recognized as an l-amino acid sensor and has been implicated in mediating cholecystokinin (CCK) secretion in response to aromatic amino acids. We investigated whether direct detection of l-phenylalanine (l-Phe) by CaSR results in CCK secretion in the native I cell. Fluorescence-activated cell sorting of duodenal I cells from CCK-enhanced green fluorescent protein (eGFP) transgenic mice demonstrated CaSR gene expression. Immunostaining of fixed and fresh duodenal tissue sections confirmed CaSR protein expression. Intracellular calcium fluxes were CaSR dependent, stereoselective for l-Phe over d-Phe, and responsive to type II calcimimetic cinacalcet in CCK-eGFP cells. Additionally, CCK secretion by an isolated I cell population was increased by 30 and 62% in response to l-Phe in the presence of physiological (1.26 mM) and superphysiological (2.5 mM) extracellular calcium concentrations, respectively. While the deletion of CaSR from CCK-eGFP cells did not affect basal CCK secretion, the effect of l-Phe or cinacalcet on intracellular calcium flux was lost. In fact, both secretagogues, as well as superphysiological Ca2+, evoked an unexpected 20–30% decrease in CCK secretion compared with basal secretion in CaSR−/− CCK-eGFP cells. CCK secretion in response to KCl or tryptone was unaffected by the absence of CaSR. The present data suggest that CaSR is required for hormone secretion in the specific response to l-Phe by the native I cell, and that a receptor-mediated mechanism may inhibit hormone secretion in the absence of a fully functional CaSR.Keywords
This publication has 47 references indexed in Scilit:
- GPR93 activation by protein hydrolysate induces CCK transcription and secretion in STC-1 cellsAmerican Journal of Physiology-Gastrointestinal and Liver Physiology, 2007
- Identification of a protein hydrolysate responsive G protein-coupled receptor in enterocytesAmerican Journal of Physiology-Gastrointestinal and Liver Physiology, 2007
- Taste Receptors in the Gastrointestinal Tract II.l-Amino acid sensing by calcium-sensing receptors: implications for GI physiologyAmerican Journal of Physiology-Gastrointestinal and Liver Physiology, 2006
- Possible role of PEPT1 in gastrointestinal hormone secretionBiochemical and Biophysical Research Communications, 2005
- The Venus Fly Trap Domain of the Extracellular Ca2+-sensing Receptor Is Required for l-Amino Acid SensingJournal of Biological Chemistry, 2004
- Expression of the Calcium-Sensing Receptor in Pancreatic Islet B-CellsBiochemical and Biophysical Research Communications, 1999
- Cao-sensing receptor (CaR)-mediated activation of K+ channels is blunted in CaR gene-deficient mouse neuronsNeuroReport, 1997
- Immunolocalization and pharmacological relevance of oligopeptide transporter PepT1 in intestinal absorption of β‐lactam antibioticsFEBS Letters, 1996
- Modulation by Polycationic Ca2+-Sensing Receptor Agonists of Nonselective Cation Channels in Rat Hippocampal NeuronsBiochemical and Biophysical Research Communications, 1996
- Cloning and characterization of an extracellular Ca2+-sensing receptor from bovine parathyroidNature, 1993