Qi Y, Ogunbunmi E M, Freund E A, Timerman A P, Fleischer S
Department of Molecular Biology, Vanderbilt University, Nashville, Tennessee 37235, USA.
J Biol Chem. 1998 Dec 25;273(52):34813-9. doi: 10.1074/jbc.273.52.34813.
The ryanodine receptor/calcium release channel (RyR1) of sarcoplasmic reticulum from rabbit skeletal muscle terminal cisternae (TC) contains four tightly associated FK506-binding proteins (FKBP12). Dissociation and reconstitution studies have shown that RyR1 can be modulated by FKBP12, which helps to maintain the channel in the quiescent state. In this study, we found that the association of FKBP with RyR1 of skeletal muscle is common to each of the five classes of vertebrates. TC from skeletal muscle representing animals from different vertebrates, i.e. mammals (rabbit), birds (chicken), reptiles (turtle), fish (salmon and rainbow trout), and amphibians (frog), were isolated. For each, we find the following: 1) FKBP12 is localized to the TC (there are four FKBP binding sites/ryanodine receptor); 2) soluble FKBP exchanges with the bound form on RyR1 of TC; 3) release of FKBP from terminal cisternae by drug (FK590) treatment leads to a significant reduction in the net calcium loading rate, consistent with channel activation (the calcium loading rate is restored to the control value by reconstitution with FKBP12); and 4) RyR1 of skeletal muscle TC can bind to and exchange with either FKBP12 or FKBP12.6 (FKBP12.6 is the novel FKBP isoform found selectively associated with RyR2 of dog cardiac sarcoplasmic reticulum). We conclude that FKBP is an integral part of the RyR1 of skeletal muscle in each of the classes of vertebrate animals. The studies are consistent with a role for FKBP in skeletal muscle excitation-contraction coupling.
来自兔骨骼肌终末池（TC）肌浆网的兰尼碱受体/钙释放通道（RyR1）包含四个紧密结合的FK506结合蛋白（FKBP12）。解离和重组研究表明，FKBP12可调节RyR1，有助于使通道维持在静息状态。在本研究中，我们发现FKBP与骨骼肌RyR1的结合在五类脊椎动物中均很常见。我们分离了代表不同脊椎动物的骨骼肌终末池，即哺乳动物（兔）、鸟类（鸡）、爬行动物（龟）、鱼类（鲑鱼和虹鳟鱼）和两栖动物（蛙）。对于每一种动物，我们发现以下几点：1）FKBP12定位于终末池（每个兰尼碱受体有四个FKBP结合位点）；2）可溶性FKBP与终末池RyR1上的结合形式进行交换；3）用药物（FK590）处理使FKBP从终末池释放，导致净钙装载速率显著降低，这与通道激活一致（通过用FKBP12重组可使钙装载速率恢复到对照值）；4）骨骼肌终末池的RyR1可与FKBP12或FKBP12.6结合并进行交换（FKBP12.6是新发现的选择性与犬心肌肌浆网RyR2相关的FKBP同工型）。我们得出结论，在每一类脊椎动物中，FKBP都是骨骼肌RyR1的一个组成部分。这些研究结果与FKBP在骨骼肌兴奋-收缩偶联中的作用一致。
