Streptozotocin-Induced Diabetes Increases Disulfide Bond Formation on Cardiac Ryanodine Receptor (RyR2)
作者:Keshore R. Bidasee、Karuna Nallani、Henry R. Besch、U. Deniz Dincer
DOI:10.1124/jpet.102.046201
日期:2003.6
In a previous study, we showed that after 6 weeks of streptozotocin-induced diabetes (6D), expression of type 2 ryanodine receptor calcium-release channels (RyR2) did not change significantly in rat hearts. However, the ability of this protein to bind [3H]ryanodine was compromised. Loss in activity therefore resulted from diabetes-induced increases in post-translational modifications on RyR2. In the present study, the effects of diabetes on one type of modification, namely, changes in oxidative state of reactive sulfhydryls was investigated. RyR2 protein from 6D bound 42.3 ± 7.6 less [3H]ryanodine than RyR2 from controls (6C). The loss in binding was minimized with 2 weeks of insulin treatment initiated after 4 weeks of diabetes (77.8 ± 5.5% of 6C). Pretreating RyR2 from 6D with 2 mM dithiothreitol in vitro increases [3H]ryanodine binding by 60.8 ± 5.3%. Dithiothreitol pretreatment of RyR2 from 6C increased [3H]ryanodine binding by 16.8 ± 4.3%. The reagent pyrocoll interacts with distinct classes of free sulfhydryl groups on 6C RyR2 to induce two major effects. At concentrations ≤10 μM, it deactivates RyR2 (decreases [3H]ryanodine binding), whereas at higher concentrations it activates them (increases [3H]ryanodine binding). This reagent was unable to activate RyR2 from 6D. Although RyR2 from insulin-treated animals was deactivated by low concentrations of pyrocoll, it was only partially activated at higher concentrations. These data suggest that the dysfunction of RyR2 induced by diabetes may be due in part to formation of disulfide bonds between adjacent sulfhydryl groups and that these changes were attenuated with insulin treatment.
在之前的一项研究中,我们发现在链脲佐菌素诱导糖尿病(6D)6 周后,大鼠心脏中 2 型雷诺丁受体钙释放通道(RyR2)的表达没有发生显著变化。然而,这种蛋白质结合[3H]雷诺丁的能力却受到了影响。因此,活性的丧失是糖尿病引起的 RyR2 翻译后修饰增加的结果。本研究调查了糖尿病对一种修饰的影响,即活性巯基氧化状态的变化。与对照组的 RyR2 相比(6C),6D 的 RyR2 蛋白结合[3H]雷诺丁的量减少了 42.3 ± 7.6。在糖尿病 4 周后开始进行为期 2 周的胰岛素治疗(6C 的 77.8 ± 5.5%),结合力的损失降至最低。在体外用 2 mM 二硫苏糖醇预处理 6D 中的 RyR2,可使[3H]雷诺丁结合率提高 60.8 ± 5.3%。对 6C 的 RyR2 进行二硫苏糖醇预处理可使[3H]雷诺丁结合率提高 16.8 ± 4.3%。试剂吡咯与 6C RyR2 上不同类别的游离巯基相互作用,产生两种主要效应。当浓度≤10 μM时,它使RyR2失活(减少[3H]雷诺丁结合),而当浓度较高时,它使RyR2活化(增加[3H]雷诺丁结合)。这种试剂无法激活 6D 的 RyR2。虽然胰岛素处理动物的 RyR2 在低浓度的 pyrocoll 作用下失活,但在较高浓度时仅部分被激活。这些数据表明,糖尿病诱导的 RyR2 功能障碍可能部分是由于相邻巯基之间形成了二硫键,而胰岛素治疗可减轻这些变化。