Chakrabarti R, Chang J Y, Erickson K L
Department of Cell Biology and Human Anatomy, University of California, School of Medicine, Davis 95616-8643, USA.
J Cell Biochem. 1995 Jul;58(3):344-59. doi: 10.1002/jcb.240580308.
In this study, we showed that cross-linking CD3 molecules on the T cell surface resulted in Ca2+ release from the intracellular stores followed by a sustained Ca2+ influx. Inhibition of release with TMB-8 did not block the influx. However, inhibition of phospholipase C activity suppressed both Ca2+ release and influx. Once activated, the influx pathway remained open in the absence of further hydrolysis of PIP2. Thapsigargin, a microsomal Ca(2+)-ATPase inhibitor, stimulated Ca2+ entry into the cells by a mechanism other than emptying Ca2+ stores. In addition, Ca2+ entry into the Ca(2+)-depleted cells was stimulated by low basal level of cytosolic Ca2+, not by the emptying of intracellular Ca2+ stores. Both the Ca2+ release and influx were dependent on high and low concentrations of extracellular Ca2+. At low concentrations, Mn2+ entered the cell through the Ca2+ influx pathway and quenched the sustained phase of fluorescence; whereas, at higher Mn2+ concentration both the transient and the sustained phases of fluorescence were quenched. Moreover, Ca2+ release was inhibited by low concentrations of Ni2+, La3+, and EGTA, while Ca2+ influx was inhibited by high concentrations. Thus, in T cells Ca2+ influx occurs independently of IP3-dependent Ca2+ release. However, some other PIP2 hydrolysis-dependent event was involved in prolonged activation of Ca2+ influx. Extracellular Ca2+ influenced Ca2+ release and influx through the action of two plasma membrane Ca2+ entry pathways with different pharmacological and biochemical properties.
在本研究中，我们发现T细胞表面的CD3分子交联会导致细胞内储存库释放Ca2+，随后是持续的Ca2+内流。用TMB - 8抑制释放并未阻断内流。然而，抑制磷脂酶C活性会同时抑制Ca2+释放和内流。一旦激活，在没有进一步水解磷脂酰肌醇 - 4,5 - 二磷酸（PIP2）的情况下，内流途径仍保持开放。毒胡萝卜素是一种微粒体Ca(2+)-ATP酶抑制剂，它通过排空Ca2+储存库以外的机制刺激Ca2+进入细胞。此外，低基础水平的胞质Ca2+刺激Ca2+进入Ca(2+)-耗尽的细胞，而不是通过排空细胞内Ca2+储存库。Ca2+释放和内流均依赖于细胞外Ca2+的高浓度和低浓度。在低浓度下，Mn2+通过Ca2+内流途径进入细胞并淬灭荧光的持续阶段；而在较高的Mn2+浓度下，荧光的瞬态和持续阶段均被淬灭。此外，低浓度的Ni2+、La3+和乙二醇双乙醚四乙酸（EGTA）抑制Ca2+释放，而高浓度抑制Ca2+内流。因此，在T细胞中，Ca2+内流独立于IP3依赖性Ca2+释放而发生。然而，一些其他依赖于PIP2水解的事件参与了Ca2+内流的延长激活。细胞外Ca2+通过两种具有不同药理和生化特性的质膜Ca2+进入途径的作用影响Ca2+释放和内流。
