Ricard I, Martel J, Dupuis L, Dupuis G, Payet M D
Program Group of the Medical Research Council of Canada on Immuno-Cardiovascular Interactions, Faculty of Medicine, University of Sherbrooke, Quebec, Canada.
Cell Signal. 1997 Feb;9(2):197-206. doi: 10.1016/s0898-6568(96)00141-6.
Caffeine and ryanodine triggered an increase in [Ca2+]i (73 +/- 22 and 61 +/- 18 nM, respectively) in Jurkat cell populations that was independent of external Ca2+. In individual cells, caffeine and ryanodine induced Ca2+ spikes. Jurkat cell populations initially exposed to caffeine did not respond further to ryanodine and vice versa, suggesting an overlap of the Ca2+ pool that was contained within the thapsigargin-sensitive Ca2+ reserve. [3H]ryanodine bound to a single class of sites of Jurkat microsomes (KD, 18.4 +/- 5.7 nM; Bmax, 24.3 +/- 7.7 fmol/mg protein). Photolytic release (Nitr5) of caged Ca2+ induced a time-dependent increase of Ca2+ in individual Jurkat cells. The profile of the release of Ca2+ was characterized, 1) by a kinetic (0.55 +/- 0.07 nM s-1) slower than the Ca2+ response to caffeine (3.93 +/- 0.66 nM s-1) or to ryanodine (3.96 +/- 0.94 nM s-1), 2) by a release of Ca2+ (131 +/- 43 nM) that slowly returned to baseline and during which low amplitude oscillations were present (room temperature) or Ca2+ spikes (37 degrees C) and, 3) by a lack of dependency on an influx of Ca2+. Inhibitors of CICR (ruthenium red and 1-octanol) prevented the photolysis-dependent increase in [Ca2+]i but not the InsP3-dependent Ca2+ response. Our data suggest that Jurkat T cells possess at least two Ca2+ pools, one that is sensitive to InsP3 and one that is insensitive. These two Ca2+ pools may be involved in a CICR that generates spontaneous Ca2+ spikes and oscillations in these cells.
咖啡因和兰尼碱可使Jurkat细胞群体中的[Ca2+]i增加（分别为73±22和61±18 nM），且这种增加不依赖于细胞外Ca2+。在单个细胞中，咖啡因和兰尼碱可诱导Ca2+尖峰。最初暴露于咖啡因的Jurkat细胞群体对兰尼碱不再有进一步反应，反之亦然，这表明毒胡萝卜素敏感的Ca2+储备中所含的Ca2+池存在重叠。[3H]兰尼碱与Jurkat微粒体的单一类位点结合（KD，18.4±5.7 nM；Bmax，24.3±7.7 fmol/mg蛋白质）。笼锁Ca2+的光解释放（Nitr5）可诱导单个Jurkat细胞中Ca2+随时间增加。Ca2+释放的特征如下：1）动力学（0.55±0.07 nM s-1）比Ca2+对咖啡因（3.93±0.66 nM s-1）或兰尼碱（3.96±0.94 nM s-1）的反应慢；2）Ca2+释放量（131±43 nM）缓慢恢复至基线，在此期间存在低幅度振荡（室温）或Ca2+尖峰（37℃）；3）不依赖于Ca2+内流。CICR抑制剂（钌红和1-辛醇）可阻止光解依赖的[Ca2+]i增加，但不能阻止InsP3依赖的Ca2+反应。我们的数据表明，Jurkat T细胞至少拥有两个Ca2+池，一个对InsP3敏感，一个不敏感。这两个Ca2+池可能参与了在这些细胞中产生自发Ca2+尖峰和振荡的CICR。
