Properties of easily releasable myofilaments: are they the first step in myofibrillar protein turnover?
Properties of easily releasable myofilaments: are they the first step in myofibrillar protein turnover?
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DOI：
10.1152/ajpcell.00022.2009
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发表时间：
2009-06-01
影响因子：
5.5
通讯作者：
Goll, Darrel E.
中科院分区：
文献类型：
--
作者：
Neti, Girija;Novak, Stefanie M.;Goll, Darrel E.
Neti G，Novak SM，Thompson VF，Goll DE.易释放肌丝的特性：它们是肌原纤维蛋白转换的第一步吗？美国生理学杂志细胞生理学296：C1383-C1390，2009年。首次发表于2009年3月25日; doi：10.1152/ajpcell.00022.2009。肌原纤维蛋白必须从肌原纤维中去除，然后才能在功能肌细胞中代谢。目前还不确定如何在不破坏肌原纤维收缩功能的情况下完成这种去除。已经提出，钙蛋白酶可以从肌原纤维去除外层的细丝，作为肌原纤维蛋白质周转的第一步。几项研究发现，肌丝可以通过在ATP存在下研磨而从肌原纤维中去除。这些容易释放的肌丝（ERMs）被认为是肌原纤维蛋白周转的中间体。然而，目前尚不清楚ERMs是否是肌肉中可识别的实体，或者额外的研磨是否会去除更多的肌丝，直到肌原纤维消失，以及钙蛋白酶是否可以从完整的肌原纤维释放ERMs。本研究表明，很少的ERMs可以从残留物中获得后，第一次去除ERMs，和ERMs的产量从洗得很好的肌原纤维减少，可能是因为一些ERMs已被删除的洗涤过程。轻度钙蛋白酶治疗肌原纤维释放的细丝，有多肽组成，超微结构相似的ERMs。钙蛋白酶释放的ERMs的产量是正常产量的两到三倍。因此，ERMs是肌原纤维中可识别的实体，并且钙蛋白酶释放与ERMs相似的细丝。ERMs在肌原纤维蛋白周转中的作用尚不清楚，因为只有肌原纤维表面的细丝才会翻转，并且发育过程中肌原纤维蛋白亚型的变化不能通过ERMs机制发生。
Neti G, Novak SM, Thompson VF, Goll DE. Properties of easily releasable myofilaments: are they the first step in myofibrillar protein turnover? Am J Physiol Cell Physiol 296: C1383-C1390, 2009. First published March 25, 2009; doi:10.1152/ajpcell.00022.2009.-Myofibrillar proteins must be removed from the myofibril before they can be turned over metabolically in functioning muscle cells. It is uncertain how this removal is accomplished without disruption of the contractile function of the myofibril. It has been proposed that the calpains could remove the outer layer of filaments from myofibrils as a first step in myofibrillar protein turnover. Several studies have found that myofilaments can be removed from myofibrils by trituration in the presence of ATP. These easily releasable myofilaments (ERMs) were proposed to be intermediates in myofibrillar protein turnover. It was unclear, however, whether the ERMs were an identifiable entity in muscle or whether additional trituration would remove more myofilaments until the myofibril was gone and whether calpains could release ERMs from intact myofibrils. The present study shows that few ERMs could be obtained from the residue after the first removal of ERMs, and the yield of ERMs from well-washed myofibrils was reduced, probably because some ERMs had been removed by the washing process. Mild calpain treatment of myofibrils released filaments that had a polypeptide composition and were ultrastructurally similar to ERMs. The yield of calpain-released ERMs was two-to threefold greater than the normal yield. Hence, ERMs are an identifiable entity in myofibrils, and calpain releases filaments that are similar to ERMs. The role of ERMs in myofibrillar protein turnover is unclear, because only filaments on the surface of the myofibril would turn over, and changes in myofibrillar protein isoforms during development could not occur via the ERM mechanism.