Mack M M, Molinski T F, Buck E D, Pessah I N
Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis 95616.
J Biol Chem. 1994 Sep 16;269(37):23236-49.
Macrocyclic natural products derived from bromotyrosine isolated from the sponge Ianthella basta are shown to selectively modulate the skeletal isoform of the ryanodine-sensitive sarcoplasmic reticulum calcium channel by a novel mechanism involving the FKBP12/RyR-1 complex. Bastadins 5, 7, and the newly identified isomer of bastadin 5, bastadin 19, show marked differences in potency and efficacy toward activation of the binding of [3H]ryanodine. In physiological salt, bastadin 5 (5 microM) increases the [3H]ryanodine binding capacity of SR membranes 5-fold, by stabilizing the high affinity conformation of RyR-1 for ryanodine without shifting the affinity of the activator site for Ca2+ or altering the response to caffeine or adenine nucleotides. Bastadin 5 decreases the inhibitory potency of Mg2+ 8-fold and high (> 100 microM) Ca2+ 5-fold. Bastadin 5 inhibits Ca2+ uptake into SR vesicles and enhances Ca(2+)-induced Ca2+ release 8-fold. Bastadin 5 increases single-channel open dwell time, tau 1 and tau 2, 65- and 92-fold, respectively, without changing unitary conductance for Cs+ (450 picosiemans) or open probability. Most significant is the finding that the unique actions of bastadin 5 on [3H]ryanodine binding and Ca2+ transport are antagonized by the immunosuppressant FK506. FK506 alone weakly enhances the binding of [3H]ryanodine, compared to bastadin 5. However, FK506 diminishes bastadin 5-induced changes in [3H]ryanodine binding and Ca2+ transport without altering the efficacy of adenine nucleotides. Unlike FK506, bastadin 5 does not directly promote the dissociation of FKBP12 from the RyR-1 membrane complex; however, it markedly enhances the release of FKBP12 induced by FK506. These results suggest that the bastadin 5 effector site is a novel modulatory domain on FKBP12. Bastadins represent a new class of compounds to gain insight into the functional interactions between FKBP12 and RyR-1.
从海绵Ianthella basta中分离得到的源自溴酪氨酸的大环天然产物，被证明可通过一种涉及FKBP12/RyR - 1复合体的新机制，选择性地调节兰尼碱敏感的肌浆网钙通道的骨骼肌异构体。巴斯他汀5、7以及新鉴定出的巴斯他汀5异构体巴斯他汀19，在对[3H]兰尼碱结合激活的效力和效果上表现出显著差异。在生理盐溶液中，巴斯他汀5（5微摩尔）可使肌浆网（SR）膜的[3H]兰尼碱结合能力提高5倍，这是通过稳定RyR - 1对兰尼碱的高亲和力构象实现的，而不会改变激活位点对Ca2+的亲和力，也不会改变对咖啡因或腺嘌呤核苷酸的反应。巴斯他汀5可使Mg2+的抑制效力降低8倍，使高浓度（>100微摩尔）Ca2+的抑制效力降低5倍。巴斯他汀5可抑制Ca2+摄取到SR囊泡中，并使Ca2+诱导的Ca2+释放增强8倍。巴斯他汀5可使单通道开放驻留时间tau 1和tau 2分别增加65倍和92倍，而不改变Cs+的单位电导（450皮西门子）或开放概率。最显著的发现是，免疫抑制剂FK506可拮抗巴斯他汀5对[3H]兰尼碱结合和Ca2+转运的独特作用。与巴斯他汀5相比，单独使用FK506对[3H]兰尼碱结合的增强作用较弱。然而，FK506可减少巴斯他汀5诱导的[3H]兰尼碱结合和Ca2+转运的变化，而不改变腺嘌呤核苷酸的效力。与FK506不同，巴斯他汀5不会直接促进FKBP12从RyR - 1膜复合体上解离；然而，它可显著增强FK506诱导的FKBP12释放。这些结果表明，巴斯他汀5效应位点是FKBP12上一个新的调节结构域。巴斯他汀代表了一类新的化合物，有助于深入了解FKBP12与RyR - 1之间的功能相互作用。
