Li Hongyan, Cook John D, Terry Monica, Spitzer Nicholas C, Ferrari Michael B
Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas, USA.
Dev Dyn. 2004 Feb;229(2):231-42. doi: 10.1002/dvdy.10428.
The highly ordered arrangement of sarcomeric myosin during striated muscle development requires spontaneous calcium (Ca(2+)) transients. Here, we show that blocking transients also compromises patterned assembly of actin thin filaments, titin, and capZ. Because a conserved temporal assembly pattern has been described for these proteins, selective inhibitors of either thick or thin filament formation were used to determine their relative temporal interdependencies. For example, inhibition of myosin light chain kinase (MLCK) by application of a specific inhibitory peptide or phorbol myistate acetate (PMA) disrupts myosin assembly without significantly affecting formation of actin bands. The MLCK inhibitor ML-7, however, disrupted actin as well as myosin. Surprisingly, agents that interfere with actin dynamics, such as cytochalasin D, produced only minor organizational disruptions in actin, capZ, and titin staining. However, cytochalasin D and other actin disrupting compounds significantly perturbed myosin organization. The results indicate that (1) Ca(2+) transients regulate one or more of the earliest steps in sarcomere formation, (2) mature actin filaments can assemble independently of myosin band formation, and (3) myosin thick filament assembly is extremely sensitive to disruption of either the actin or titin filament systems.
横纹肌发育过程中肌节肌球蛋白的高度有序排列需要自发的钙（Ca(2+)）瞬变。在此，我们表明阻断瞬变也会损害肌动蛋白细肌丝、肌联蛋白和帽Z蛋白的模式组装。由于已描述了这些蛋白质的保守时间组装模式，因此使用粗肌丝或细肌丝形成的选择性抑制剂来确定它们相对的时间依赖性。例如，通过应用特定抑制肽或佛波醇肉豆蔻酸酯乙酸盐（PMA）抑制肌球蛋白轻链激酶（MLCK）会破坏肌球蛋白组装，而不会显著影响肌动蛋白带的形成。然而，MLCK抑制剂ML-7会破坏肌动蛋白以及肌球蛋白。令人惊讶的是，干扰肌动蛋白动力学的试剂，如细胞松弛素D，只会对肌动蛋白、帽Z蛋白和肌联蛋白染色产生轻微的组织破坏。然而，细胞松弛素D和其他破坏肌动蛋白的化合物会显著扰乱肌球蛋白的组织。结果表明：（1）Ca(2+)瞬变调节肌节形成中最早的一个或多个步骤；（2）成熟的肌动蛋白丝可以独立于肌球蛋白带的形成进行组装；（3）肌球蛋白粗肌丝组装对肌动蛋白或肌联蛋白丝系统的破坏极为敏感。
