Isoforms of protein 4.1 are differentially distributed in heart muscle cells: relation of 4.1R and 4.1G to components of the Ca2+ homeostasis system.
Isoforms of protein 4.1 are differentially distributed in heart muscle cells: relation of 4.1R and 4.1G to components of the Ca2+ homeostasis system.
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DOI：
10.1016/j.yexcr.2012.03.003
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发表时间：
2012-08
影响因子：
3.7
通讯作者：
J. Pinder;P. Taylor-Harris;P. Bennett;Edward Carter;N. Hayes;M. King;M. Holt;A. Maggs;P. Gascard;A. Baines
中科院分区：
文献类型：
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作者：
J. Pinder;P. Taylor-Harris;P. Bennett;Edward Carter;N. Hayes;M. King;M. Holt;A. Maggs;P. Gascard;A. Baines
4.1蛋白质是细胞骨架衔接蛋白，其与某些膜的机械稳定性的控制以及不同跨膜蛋白的细胞积累和细胞表面展示有关。四种哺乳动物4.1蛋白中的一种，4.1R（80 kDa/120 kDa同种型），最近已显示是心脏中几种离子转运蛋白的正常运作所需的（Stagg MA等人，Circ Res，2008; 103：855-863）。其他三种（4.1G，4.1N和4.1B）在心脏中基本上没有特征。在这里，我们使用特异性抗体来检测它们在左心室中的表达、分布和新的活性。我们用免疫荧光和免疫印迹法检测到4.1R、4.1G和4.1N，但未检测到4.1B。4.1N和4.1G只有一种剪接变体，而4.1R有几种形式。4.1N与4.1R一样，存在于闰盘中，但与4.1R不同，它不定位于侧质膜。4.1R和4.1N都在内部结构中，在光学显微镜的分辨率水平上，接近Z盘（可能是T小管）。4.1G也存在于胞内结构中，部分与肌浆网相吻合。4.1G与spectrin和SERCA 2形成免疫沉淀复合物。80 kDa的4.1R存在于富含闰盘的亚细胞组分中，在非变性条件下抵抗溶解的复合物中。在闰盘处，4.1R不与粘附连接蛋白β-连环蛋白共定位，但与其他质膜信号蛋白Na/K-ATP酶和Na/Ca交换剂NCX 1重叠。我们的结论是，4.1蛋白质的异构体差异划分在心脏中，它们形成特定的复合物与心肌细胞钙代谢的核心蛋白质。
The 4.1 proteins are cytoskeletal adaptor proteins that are linked to the control of mechanical stability of certain membranes and to the cellular accumulation and cell surface display of diverse transmembrane proteins. One of the four mammalian 4.1 proteins, 4.1R (80kDa/120kDa isoforms), has recently been shown to be required for the normal operation of several ion transporters in the heart (Stagg MA et al. Circ Res, 2008; 103: 855–863). The other three (4.1G, 4.1N and 4.1B) are largely uncharacterised in the heart. Here, we use specific antibodies to characterise their expression, distribution and novel activities in the left ventricle. We detected 4.1R, 4.1G and 4.1N by immunofluorescence and immunoblotting, but not 4.1B. Only one splice variant of 4.1N and 4.1G was seen whereas there are several forms of 4.1R. 4.1N, like 4.1R, was present in intercalated discs, but unlike 4.1R, it was not localised at the lateral plasma membrane. Both 4.1R and 4.1N were in internal structures that, at the level of resolution of the light microscope, were close to the Z-disc (possibly T-tubules). 4.1G was also in intracellular structures, some of which were coincident with sarcoplasmic reticulum. 4.1G existed in an immunoprecipitable complex with spectrin and SERCA2. 80kDa 4.1R was present in subcellular fractions enriched in intercalated discs, in a complex resistant to solubilization under non-denaturing conditions. At the intercalated disc 4.1R does not colocalise with the adherens junction protein, β-catenin, but does overlap with the other plasma membrane signalling proteins, the Na/K-ATPase and the Na/Ca exchanger NCX1. We conclude that isoforms of 4.1 proteins are differentially compartmentalised in the heart, and that they form specific complexes with proteins central to cardiomyocyte Ca2+metabolism.