Calcium-sensing receptor mediates phenylalanine-induced cholecystokinin secretion in enteroendocrine STC-1 cells.
Intraluminal L-phenylalanine (Phe) stimulates cholecystokinin (CCK) secretion in vivo and in vitro. However, the cellular mechanism by which CCK-producing enteroendocrine cells sense Phe is unknown. The calcium-sensing receptor (CaR) can sense amino acids, and is expressed in the gastrointestinal tract. In the present study, we examined whether CaR functions as a receptor for Phe in CCK-producing enteroendocrine cells. CCK secretion and intracellular Ca2+ concentration in response to Phe were measured in the murine CCK-producing enteroendocrine cell line STC-1 at various extracellular Ca2+ concentrations or after treatment with a CaR antagonist. At more than 20 mm, Phe induced dose-dependent CCK secretion and intracellular Ca2+ mobilization in STC-1 cells. In the presence of 3.0 mm extracellular Ca2+, 10 and 20 mm Phe induced significantly higher CCK secretion than under normal conditions (1.2 mm extracellular Ca2+). Intracellular Ca2+ mobilization, induced by 10 or 20 mm Phe, was also enhanced by increasing extracellular Ca2+ concentrations. In addition, intracellular Ca2+ mobilization induced by addition of extracellular Ca2+ was augmented by the presence of Phe. These results closely match the known CaR properties. Treatment with a specific CaR antagonist (NPS2143) completely inhibited Phe-induced CCK secretion and the latter phase of intracellular Ca2+ mobilization. CaR mRNA expression was demonstrated by RT-PCR in STC-1 cells, as well as in other mouse tissues including the kidney, thyroid, stomach and intestine. In conclusion, CaR functions as a receptor for Phe, stimulating CCK secretion in enteroendocrine STC-1 cells.
Hira
Tohru
T
Division of Applied Biosciences, Research Faculty of Agriculture, Hokkaido University, Sapporo, Japan. hira@chem.agr.hokudai.ac.jp
Nakajima
Shingo
S
Eto
Yuzuru
Y
Hara
Hiroshi
H
D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002460:Cell Line; D002766:Cholecystokinin / Q000378:metabolism*; D019858:Enteroendocrine Cells / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D010649:Phenylalanine / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D044169:Receptors, Calcium-Sensing / Q000235:genetics / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism
D012333:RNA, Messenger; D044169:Receptors, Calcium-Sensing; D010649:Phenylalanine; D002766:Cholecystokinin; D012964:Sodium; D002118:Calcium