Regulation of the Sarcoplasmic Reticulum Calcium Pump by Divergent Phospholamban Isoforms in Zebrafish
Regulation of the Sarcoplasmic Reticulum Calcium Pump by Divergent Phospholamban Isoforms in Zebrafish
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DOI：
10.1074/jbc.m114.585604
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发表时间：
2015-03-13
影响因子：
4.8
通讯作者：
Young, Howard S.
中科院分区：
文献类型：
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作者：
Gorski, Przennek A.;Trieber, Catharine A.;Young, Howard S.
肌浆网钙泵（SERCA）受小积分膜蛋白磷蛋白（PLN）和肌磷脂（SLN）的调控。这些调节因子有同源的跨膜区域，但它们在细胞质和管腔结构域不同。虽然哺乳动物中PLN和SLN的序列实际上是不变的，但它们在鱼类中是不同的。斑马鱼（zf）似乎拥有多个PLN亚型，其中一个包含18个序列变异和一个独特的管腔延伸。该异构体（zfPLN）的表征表明，SERCA的抑制和磷酸化逆转与人类PLN相当。为了了解zfPLN的序列变化，我们将zfPLN的N端、连接体和C端转移到人的PLN上，构建了嵌合体。含有n端结构域的嵌合体导致轻度功能丧失，而含有连接子结构域的嵌合体导致功能增强。后一种效应是由于PLN连接区基本残基的变化。去除zfPLN独特的管腔结构域（(53)SFHGM）导致功能丧失，而将该结构域添加到人类PLN中对SERCA抑制的影响很小。我们得出结论，管腔延伸有助于SERCA抑制，但仅在zfPLN的背景下。虽然这个结构域与SLN的腔尾不同，但zfPLN似乎使用了PLN-SLN的混合抑制机制。重要的是，不同的斑马鱼PLN异构体提出了一种有趣的可能性，即肌浆网钙处理和心脏收缩性可能受到PLN功能变异的差异表达的调节。
The sarcoplasmic reticulum calcium pump (SERCA) is regulated by the small integral membrane proteins phospholamban (PLN) and sarcolipin (SLN). These regulators have homologous transmembrane regions, yet they differ in their cytoplasmic and luminal domains. Although the sequences of PLN and SLN are practically invariant among mammals, they vary in fish. Zebrafish (zf) appear to harbor multiple PLN isoforms, one of which contains 18 sequence variations and a unique luminal extension. Characterization of this isoform (zfPLN) revealed that SERCA inhibition and reversal by phosphorylation were comparable with human PLN. To understand the sequence variations in zfPLN, chimeras were created by transferring the N terminus, linker, and C terminus of zfPLN onto human PLN. A chimera containing the N-terminal domain resulted in a mild loss of function, whereas a chimera containing the linker domain resulted in a gain of function. This latter effect was due to changes in basic residues in the linker region of PLN. Removing the unique luminal domain of zfPLN ((53)SFHGM) resulted in loss of function, whereas adding this domain to human PLN had a minimal effect on SERCA inhibition. We conclude that the luminal extension contributes to SERCA inhibition but only in the context of zfPLN. Although this domain is distinct from the SLN luminal tail, zfPLN appears to use a hybrid PLN-SLN inhibitory mechanism. Importantly, the different zebrafish PLN isoforms raise the interesting possibility that sarcoplasmic reticulum calcium handling and cardiac contractility may be regulated by the differential expression of PLN functional variants.