Department of Pharmacology, University of Oxford, Oxford, United Kingdom.
School of Medicine, University of St. Andrews, St. Andrew, United Kingdom.
Biophys J. 2014 Feb 18;106(4):824-33. doi: 10.1016/j.bpj.2013.12.041.
We have previously shown that FKBP12 associates with RyR2 in cardiac muscle and that it modulates RyR2 function differently to FKBP12.6. We now investigate how these proteins affect the single-channel behavior of RyR1 derived from rabbit skeletal muscle. Our results show that FKBP12.6 activates and FKBP12 inhibits RyR1. It is likely that both proteins compete for the same binding sites on RyR1 because channels that are preactivated by FKBP12.6 cannot be subsequently inhibited by FKBP12. We produced a mutant FKBP12 molecule (FKBP12E31Q/D32N/W59F) where the residues Glu(31), Asp(32), and Trp(59) were converted to the corresponding residues in FKBP12.6. With respect to the functional regulation of RyR1 and RyR2, the FKBP12E31Q/D32N/W59F mutant lost all ability to behave like FKBP12 and instead behaved like FKBP12.6. FKBP12E31Q/D32N/W59F activated RyR1 but was not capable of activating RyR2. In conclusion, FKBP12.6 activates RyR1, whereas FKBP12 activates RyR2 and this selective activator phenotype is determined within the amino acid residues Glu(31), Asp(32), and Trp(59) in FKBP12 and Gln(31), Asn(32), and Phe(59) in FKBP12.6. The opposing but different effects of FKBP12 and FKBP12.6 on RyR1 and RyR2 channel gating provide scope for diversity of regulation in different tissues.
我们之前已经表明，FKBP12 与心肌中的 RyR2 相关联，并且它对 RyR2 功能的调节方式与 FKBP12.6 不同。现在，我们研究这些蛋白质如何影响源自兔骨骼肌的 RyR1 的单通道行为。我们的结果表明，FKBP12.6 激活 RyR1，而 FKBP12 抑制 RyR1。这两种蛋白质可能竞争 RyR1 上的相同结合位点，因为 FKBP12.6 预激活的通道不能被 FKBP12 随后抑制。我们生成了一种突变 FKBP12 分子（FKBP12E31Q/D32N/W59F），其中残基 Glu（31）、Asp（32）和 Trp（59）被转化为 FKBP12.6 中的相应残基。就 RyR1 和 RyR2 的功能调节而言，FKBP12E31Q/D32N/W59F 突变体失去了所有类似于 FKBP12 的行为能力，反而表现得像 FKBP12.6。FKBP12E31Q/D32N/W59F 激活 RyR1，但不能激活 RyR2。总之，FKBP12.6 激活 RyR1，而 FKBP12 激活 RyR2，这种选择性激活表型由 FKBP12 中的氨基酸残基 Glu（31）、Asp（32）和 Trp（59）以及 FKBP12.6 中的 Gln（31）、Asn（32）和 Phe（59）决定。FKBP12 和 FKBP12.6 对 RyR1 和 RyR2 通道门控的相反但不同的影响为不同组织中的多样性调节提供了范围。
