Thrombin Activates Ca2+-permeating Nonselective Cation Channels through Protein Kinase C in Human Umbilical Vein Endothelial Cells

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We analyzed Ca-permeating nonselective cation channels (NSCs)mediating thrombin-induced contraction of human umbilical vein endothelial cells (HUVECs). A Ca chelater, BAPTA-AM (10μM), significantly inhibited the thrombin-induced contraction of HUVECs.Thrombin induced inward currents at -60 mV in the presence of intracellular MgATP. Removal of extracellular Caﾌﾞｸﾞsignificantly decreased the currents. A selective phospholipase C inhibitor, U73122 (1μM) but not its inactive analogue, U73343 (1μM) almost completely inhibited the currents. Neither a selective inhibitor of Caﾌﾞｸﾞ-ATPase of endoplasmic reticulum, thapsigargin (1μM)nor a diacylglycerol analogue, 1-oleoyl-2-acetyl-glycerol (30μM)activated the currents. However, a selective protein kinase C inhibitor, bisindolylmaleimide I (500 nM) significantly inhibited the currents.The thrombin-induced currents were significantly inhibited by SKF96365 (50μM)but not by La(1mM), ruthenium red (10μM) or flufenamic acid (100μM). As assessed with RT-PCR, HUVECs expressed transient receptor potential(TRP)M4,7,TRPV1,2,4,TRPC1,4 and 6 subunits of NSCs.These results indicate that thrombin activates Ca-permeating NSCs containing TRPC4 through protein kinase C in HUVECs. Thus,drugs specifically inhibiting TRPC4-containing channels might be effective to control fatal diseases such as sepsis where thrombin mediates the vicious cycle between inflammation and coagulation.
2011-02-10