Obscurin Interacts with a Novel Isoform of MyBP-C Slow at the Periphery of the Sarcomeric M-Band and Regulates Thick Filament Assembly
Obscurin Interacts with a Novel Isoform of MyBP-C Slow at the Periphery of the Sarcomeric M-Band and Regulates Thick Filament Assembly
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DOI：
10.1091/mbc.e08-12-1251
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发表时间：
2009-06-15
影响因子：
3.3
通讯作者：
Kontrogianni-Konstantopoulos, Aikaterini
中科院分区：
文献类型：
--
作者：
Ackermann, Maegen A.;Hu, Li-Yen R.;Kontrogianni-Konstantopoulos, Aikaterini
Obscurin是一种多结构域蛋白，由粘附和信号传导结构域组成，在横纹肌收缩和膜结构的组织中起关键作用。过表达的第二免疫球蛋白结构域的obscurin（Ig 2）在发展中的肌管抑制组装的A-和M-带，但不是Z-盘或I-带。这种作用是由obscurin的Ig 2结构域与肌球蛋白结合蛋白-C慢（MyBP-C慢）的新亚型（对应于变体-1）的直接相互作用介导的。变体-1含有MyBP-C慢的已知形式中存在的所有结构基序，但它具有独特的COOH末端。定量逆转录-聚合酶链反应表明，MyBP-C慢变体-1在发育和成熟过程中的骨骼肌中表达。骨骼肌纤维与抗体的独特的COOH末端的变体-1的免疫标记表明，不像其他形式的MyBP-C慢，驻留在C区的A带，变体-1优先集中在M带周围，在那里它与obscurin共分布。Ig 2结构域的obscurin或obscurin的表达减少的过表达抑制变体-1整合到骨骼肌管中形成M带。总的来说，我们的实验确定了一个新的配体obscurin在M-带，MyBP-C慢变体-1，并表明它们的相互作用有助于组装的M-和A-带。
Obscurin is a multidomain protein composed of adhesion and signaling domains that plays key roles in the organization of contractile and membrane structures in striated muscles. Overexpression of the second immunoglobulin domain of obscurin (Ig2) in developing myotubes inhibits the assembly of A- and M-bands, but not Z-disks or I-bands. This effect is mediated by the direct interaction of the Ig2 domain of obscurin with a novel isoform of myosin binding protein-C slow (MyBP-C slow), corresponding to variant-1. Variant-1 contains all the structural motifs present in the known forms of MyBP-C slow, but it has a unique COOH terminus. Quantitative reverse transcription-polymerase chain reaction indicated that MyBP-C slow variant-1 is expressed in skeletal muscles both during development and at maturity. Immunolabeling of skeletal myofibers with antibodies to the unique COOH terminus of variant-1 demonstrated that, unlike other forms of MyBP-C slow that reside in the C-zones of A- bands, variant-1 preferentially concentrates around M-bands, where it codistributes with obscurin. Overexpression of the Ig2 domain of obscurin or reduction of expression of obscurin inhibited the integration of variant-1 into forming M-bands in skeletal myotubes. Collectively, our experiments identify a new ligand of obscurin at the M-band, MyBP-C slow variant-1 and suggest that their interaction contributes to the assembly of M- and A- bands.