Synergistic actions of diacylglycerol and inositol 1,4,5 trisphosphate for Ca^2＋-dependent inactivation of TRPC7 channel  

作　　者：Hua ZHANG Ryuji INOUE Juan SHI Xiao-hang JIN Yun-qing LI 

机构地区：[1]Department of Anatomy and KK Leung Brain Research Centre, The Fourth Military Medical University, Xi'an 710032, China [2]Department of Physiology, Fukuoka University School of Medicine, Fukuoka 814-0180, Japan [3]Department of Histology and Embryology, The Fourth Military Medical University, Xi'an 710032, China [4]Department of Cardiology, Xijing Hospital, Xi'an 710032, China

出　　处：《Acta Pharmacologica Sinica》2008年第1期90-97,共8页中国药理学报（英文版）

基　　金：This work was supported by the National Natural Science Foundation of China （No 30400154 and 30400329）, Innovation Research Team Program of Ministry of Education （No IRT0560）, and the National Program of Basic Research of China （No G2006CB500808）. Acknowledgement We thank Prof Yasuo MORI （University of Kyoto） for providing the plasmids of TRPC7 and mutCaM.

摘　　要：Aim： The aim of the present study was to explore the mechanism for the Ca^2＋- dependent inactivation of the canonical transient receptor potential （TRPC） 7 channel expressed in human embryonic kidney 293 cells. Method： The whole-cell patch-clamp technique was used in the study. Results： With Ca^2＋-free external solution, the perfusion of 100 μmol/L carbachol to, or dialysis of the cell with 100 μmol/L guanosine 5＇-3-O-（thio）triphosphate （GTPγS）, induced large inward currents, respectively. These currents were rapidly inhibited by the addition of 1 mmol/L Ca^2＋ into the bath, and recovery from this inhibition was only partial after the Ca^2＋ removal, unless vigorous intracellular Ca^2＋ buffering with l0 mmol/L 1,2 bis（2- aminophenoxy）ethane-N,N,N＇,N＇-tetraacetic acid （BAPTA） （plus 4 mmol/L Ca^2＋） was employed. In contrast, the current induced by a membrane-permeable analog of diacylglycerol （DAG）, 1-oleoyl-2-acetyl-sn-glycerol （OAG; 100 μmol/L） did not undergo the inhibition persisting after Ca^2＋ removal. Interestingly, the inclusion of inositol 1,4,5 trisphosphate （IP3; 100 μmol/L） in the patch pipette rendered the OAG-induced current susceptible to the persistent Ca^2＋-mediated inhibition independent of the IP3 receptor in the majority of the tested cells, as evidenced by the inability of heparin and thapsigargin in reversing the effect of IP3. Conclusion： The present results suggest that Ca^2＋ entry via the activated TRPC7 channel plays a critical role in inactivating the channel where the cooperative actions of DAG and IP3 are essentially involved.Aim： The aim of the present study was to explore the mechanism for the Ca^2＋- dependent inactivation of the canonical transient receptor potential （TRPC） 7 channel expressed in human embryonic kidney 293 cells. Method： The whole-cell patch-clamp technique was used in the study. Results： With Ca^2＋-free external solution, the perfusion of 100 μmol/L carbachol to, or dialysis of the cell with 100 μmol/L guanosine 5＇-3-O-（thio）triphosphate （GTPγS）, induced large inward currents, respectively. These currents were rapidly inhibited by the addition of 1 mmol/L Ca^2＋ into the bath, and recovery from this inhibition was only partial after the Ca^2＋ removal, unless vigorous intracellular Ca^2＋ buffering with l0 mmol/L 1,2 bis（2- aminophenoxy）ethane-N,N,N＇,N＇-tetraacetic acid （BAPTA） （plus 4 mmol/L Ca^2＋） was employed. In contrast, the current induced by a membrane-permeable analog of diacylglycerol （DAG）, 1-oleoyl-2-acetyl-sn-glycerol （OAG; 100 μmol/L） did not undergo the inhibition persisting after Ca^2＋ removal. Interestingly, the inclusion of inositol 1,4,5 trisphosphate （IP3; 100 μmol/L） in the patch pipette rendered the OAG-induced current susceptible to the persistent Ca^2＋-mediated inhibition independent of the IP3 receptor in the majority of the tested cells, as evidenced by the inability of heparin and thapsigargin in reversing the effect of IP3. Conclusion： The present results suggest that Ca^2＋ entry via the activated TRPC7 channel plays a critical role in inactivating the channel where the cooperative actions of DAG and IP3 are essentially involved.

关 键 词：canonical transient receptor potential 7 calcium  inactivation  diacylglycerol inositol 1 4 5 trisphosphate 

分 类 号：Q25[生物学—细胞生物学]