Structural alterations in cardiac calcium release units resulting from overexpression of junctin.
Structural alterations in cardiac calcium release units resulting from overexpression of junctin.
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结蛋白过度表达导致心脏钙释放单位的结构改变。
DOI：
10.1006/jmcc.2000.1295
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
Jones,LR
中科院分区：
文献类型：
--
作者：
Zhang,L;Franzini-Armstrong,C;Ramesh,V;Jones,LR
Junctin 是一种 26 kDa 的膜蛋白，可与钙释放单位的连接肌浆网内的 calsequestrin、triadin 和 ryanodine 受体 (RyR) 结合。连接蛋白的序列包括短的N端胞质结构域、单个跨膜结构域和位于肌浆网腔中的高电荷C端结构域。狗和小鼠的连接蛋白在跨膜结构域上高度保守，但管腔结构域的差异更大。为了探讨连接蛋白对心脏钙释放单位结构的贡献，我们设计了过度表达犬连接蛋白的转基因小鼠，并通过电子显微镜检查了左心室心肌。对照心肌和过度表达连接蛋白 5-10 倍的心肌中钙释放单位的总体结构相似。在两种心肌中，交界 SR 池均与外膜（质膜和横管）密切相关。水池平坦；它们含有一串 calsequestrin 珠子，并在面向外膜的一侧排列着一排脚（RyR）。 T 小管表面密度（以 T 小管轮廓周长与切片面积来测量）在转基因心肌和对照心肌中是相同的 (305 v 289 nm/nm2)。在过度表达连接蛋白的心肌中，影响连接 SR 结构的三个变化是明显的。一是连接 SR 池的拉链外观更加紧密。与对照心肌相比，过度表达时连接 SR 的宽度更窄且变化更小，并且 calsequestrin 含量更紧凑。第二个变化是将拉链连接 SR 域扩展到非连接区域，我们称之为“受挫”连接 SR。第三个变化是 SR 和 T 小管之间关联程度的增加。在连接蛋白过度表达的心肌中，连接SR池覆盖所有T小管轮廓的表面的约45%，而在对照心肌中，覆盖率为约30%。 SR 和 T 小管之间的连接关联尺寸增加。我们得出的结论是，连接蛋白表达的增加会影响连接 SR 中钙结合蛋白的堆积，并促进 SR 和 T 小管的结合。
Junctin is a 26 kDa membrane protein that binds to calsequestrin, triadin, and ryanodine receptors (RyRs) within the junctional sarcoplasmic reticulum of calcium release units. The sequence of junctin includes a short N-terminal cytoplasmic domain a single transmembrane domain, and a highly charged C-terminal domain located in the sarcoplasmic reticulum lumen. Dog and mouse junctins are highly conserved at the transmembrane domains, but the luminal domains are more divergent. To probe the contribution of junctin to the architecture of calcium release units in heart, we engineered transgenic mice overexpressing canine junctin and examined the left ventricular myocardium by electron microscopy. Overall architecture of calcium release units is similar in control myocardium and in myocardium overexpressing junctin by 5–10-fold. In both myocardia, junctional SR cisternae are closely associated with exterior membranes (plasmalemma and transverse tubules). The cisternae are flat; they contain a string of calsequestrin beads and are lined by a row of feet, or RyRs, on the side facing the exterior membranes. T tubule surface density, measured as the perimeter of T tubule profiles v area of section, is the same in transgenic and control myocardia (305 v 289 nm/nm2). Three changes affecting the junctional SR architecture are apparent in the myocardium overexpressing junctin. One is a more tightly zippered appearance of the junctional SR cisternae. The width of the junctional SR is narrower and less variable in overexpressing than in control myocardium and the calsequestrin content is more compact. A second change is the extension of zippered junctional SR domains to non-junctional regions, which we term ««frustrated»» junctional SR. A third change is an increase in the extent of association between SR and T tubules. In junctin overexpressing myocardium junctional SR cisternae cover ≡45% of the surface of all T tubule profiles, while in control myocardium the coverage is ≡30%. Junctional associations between SR and T tubules are increased in size. We conclude that the increase in junctin expression affects the packing of calsequestrin in the junctional SR and facilitates the association of SR and T tubules.
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影响因子：
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发表时间：
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影响因子：
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作者：
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