The functional expression of calcium-sensing receptors in BRL cells and related signal transduction pathway responsible for intracellular calcium elevation |
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Authors: | Wenjing Xing Guangwei Li Yuhui Xi Jin Guo Hongzhu Li Hongxia Li Weihua Zhang Li Zhang Lingyun Wu Rui Wang Changqing Xu |
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Affiliation: | 1. Department of Pathophysiology, Harbin Medical University, Harbin, 150086, China 3. Department of Biology, Lakehead University, Thunder Bay, ON, P7B 5E1, Canada 2. Bio-Pharmaceutical Key Laboratory of Heilongjiang Province, Harbin, 150086, China
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Abstract: | The calcium-sensing receptors (CaSRs) exist in a variety of tissues and cells. In 2001, Canaff et al. first identified its expression in liver tissue and primary cultured hepatocytes, and demonstrated that GdCl3 (a specific agonist of CaSR) can cause an increase in intracellular calcium and bile flow. However, authors did not elucidate its mechanisms. Therefore, this study sought to detect CaSR expression in BRL cell line, which is derived from buffalo rat liver, and to reveal the cellular signal transduction pathway by which the CaSR activation results in increased intracellular calcium by BRL cells. In this study, the expression and distribution of CaSR were detected by RT-PCR, Western blotting, and immunofluorescence, and the intracellular calcium concentration [Ca2+]i was measured using LCSM. The results showed that CaSR mRNA and protein were expressed in BRL cells and mainly distributed in cell membrane and cytoplasm. Increased extracellular calcium or GdCl3 could increase intracellular calcium concentration and CaSR expression. Moreover, this increase of [Ca2+]i could be inhibited or even abolished by U73122 (a specific inhibitor of PLC), 2-APB (an inhibitor of IP3 receptor), and thapsigargin (an inhibitor of endoplasmic reticulum calcium pump). In conclusion, CaSR is functionally expressed in BRL cells, and activation of CaSR involves in increased intracellular calcium through Gq–PLC–IP3 pathway. |
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