Maurocalcine and peptide A stabilize distinct subconductance states of ryanodine receptor type 1, revealing a proportional gating mechanism
Maurocalcine and peptide A stabilize distinct subconductance states of ryanodine receptor type 1, revealing a proportional gating mechanism
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DOI：
10.1074/jbc.m209501200
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发表时间：
2003-05-02
影响因子：
4.8
通讯作者：
Pessah, IN
中科院分区：
文献类型：
--
作者：
Chen, L;Estève, E;Pessah, IN
从蝎毒中分离得到的毛蕊花毒素（MCa）与欧前胡毒素A（imperatoxin A）有82%的同源性。这两种蝎毒素都是α（1 s）-二氢吡啶受体的II-III环肽（称为肽A（pA））的假定模拟物，并被认为作用于对骨骼肌EC偶联重要的1型兰尼碱受体（RyR 1）上的共同位点。研究了合成MCa（sMCa）和pA对RyR 1作用之间的关系。sMCa从SR囊泡中释放Ca ~（2+）（EC_（50）= 17.5 nm），其释放量可被微摩尔的兰尼定或钌红抑制。PA（0.5-40 μ m）不能诱导SR Ca ~（2+）释放。相反，PA增强Ca 2+加载到SR和完全抑制Ca 2+，咖啡因，和sMCa诱导的Ca 2+释放。这两种肽以不同的方式修饰单通道门控行为。与Cs+-携带电流，10 nm至1妈妈sMCa诱导长寿命的subconductions具有48%的特征全开状态和偶尔的过渡到29%，无论是积极的或消极的保持电位。相比之下，PA稳定的长寿命通道关闭偶尔突发过渡到65%（s1）和86%（s2）的全电导。同时观察到pA和sMCa的作用。sMCa稳定额外的亚电导状态的比例PA诱导的亚电导（即43%的PA修改的s1和s2亚状态），揭示了比例门控机制。[H-3]Ryanodine结合和表面等离子体共振分析表明，肽没有通过简单竞争RyR 1上的一类互斥位点产生比例门控而相互作用。sMCa的行动也观察到与ryanodine修饰的通道和通道缺乏亲免素12-kDa FK 506结合蛋白。这些结果提供了证据表明，sMCa和PA通过不同的机制稳定不同的RyR 1通道状态，变构稳定具有比例电导的门控状态。
Maurocalcine (MCa) isolated from Scorpio maurus palmatus venom shares 82% sequence identity with imperatoxin A. Both scorpion toxins are putative mimics of the II-III loop peptide (termed peptide A (pA)) of alpha(1s)-dihydropyridine receptor and are thought to act at a common site on ryanodine receptor type 1 (RyR1) important for skeletal muscle EC coupling. The relationship between the actions of synthetic MCa (sMCa) and pA on RyR1 were examined. sMCa released Ca2+ from SR vesicles (EC50 = 17.5 nm) in a manner inhibited by micromolar ryanodine or ruthenium red. pA (0.5-40 mum) failed to induce SR Ca2+ release. Rather, pA enhanced Ca2+ loading into SR and fully inhibited Ca2+-, caffeine-, and sMCa-induced Ca2+ release. The two peptides modified single channel gating behavior in distinct ways. With Cs+-carrying current, 10 nm to 1 mum sMCa induced long lived subconductances having 48% of the characteristic full open state and occasional transitions to 29% at either positive or negative holding potentials. In contrast, pA stabilized long lived channel closures with occasional burst transitions to 65% (s1) and 86% (s2) of the full conductance. The actions of pA and sMCa were observed in tandem. sMCa stabilized additional subconductance states proportional to pA-induced subconductances (i.e. 43% of pA-modified s1 and s2 substates), revealing a proportional gating mechanism. [H-3]Ryanodine binding and surface plasmon resonance analyses indicated that the peptides did not interact by simple competition for a single class of mutually exclusive sites on RyR1 to produce proportional gating. The actions of sMCa were also observed with ryanodine-modified channels and channels deficient in immunophilin 12-kDa FK506-binding protein. These results provide evidence that sMCa and pA stabilize distinct RyR1 channel states through distinct mechanisms that allosterically stabilize gating states having proportional conductance.