Characterization of muscle ankyrin repeat proteins in human skeletal muscle
Characterization of muscle ankyrin repeat proteins in human skeletal muscle
复制标题
DOI：
10.1152/ajpcell.00077.2017
复制
发表时间：
2017-09-01
影响因子：
5.5
通讯作者：
Murphy, Robyn M.
中科院分区：
文献类型：
--
作者：
Wette, Stefan G.;Smith, Heather K.;Murphy, Robyn M.
肌肉骨架蛋白重复蛋白(MARPs)是一类肌动蛋白相关的应激反应分子家族，在骨骼肌中可能是牵张诱导信号的转导分子。据报道，在心肌中，心肌强直蛋白重复蛋白(CARP)和糖尿病相关强直蛋白重复蛋白(DARP)在长时间拉伸后从肌动蛋白的结合部位重新分布到细胞核。然而，目前尚不清楚锚蛋白重复结构域蛋白2(AnkRd2)是否显示出类似的拉伸诱导的细胞核重分布。我们在静息的人骨骼肌中测量了以下内容：1)MARP的绝对量；2)AnkRd2和DARP在单纤维和全肌标本中的分布。AnkRd2是人体骨骼肌中含量最丰富的MARP，其含量接近3.1mU/kg，远高于DARP和鲤鱼(分别接近0.11和0.02mU/kg)。所有的DARP都被发现紧密结合在细胞骨架(或可能是核)部位。相反，AnkRd2类似于总AnkRd2的70%可在胞浆中自由扩散[包括几乎所有的磷酸化(P)AnkRd2-Ser99形式]，类似于15%结合在非核膜上，类似于15%结合在细胞骨架部位，可能在Titin的N2a区域。这些数据与Ankrd2本身或pAnkrd2-Ser99在骨骼肌中介导牵张诱导的信号传递的说法不一致，因为这些形式的Ankrd2中的大多数已经在胞浆中游离。如果Titin相关的Ankrd 2要作为拉伸敏感的信号分子，就有必要证明它是以某种尚不确定的方式被拉伸修饰的，与可扩散池不同。
Muscle ankyrin repeat proteins (MARPs) are a family of titin-associated, stress-response molecules and putative transducers of stretch-induced signaling in skeletal muscle. In cardiac muscle, cardiac ankyrin repeat protein (CARP) and diabetes-related ankyrin repeat protein (DARP) reportedly redistribute from binding sites on titin to the nucleus following a prolonged stretch. However, it is unclear whether ankyrin repeat domain protein 2 (Ankrd 2) shows comparable stretch-induced redistribution to the nucleus. We measured the following in rested human skeletal muscle: 1) the absolute amount of MARPs and 2) the distribution of Ankrd 2 and DARP in both single fibers and whole muscle preparations. In absolute amounts, Ankrd 2 is the most abundant MARP in human skeletal muscle, there being similar to 3.1 mu mol/kg, much greater than DARP and CARP (similar to 0.11 and similar to 0.02 mu mol/kg, respectively). All DARP was found to be tightly bound at cytoskeletal (or possibly nuclear) sites. In contrast, similar to 70% of the total Ankrd 2 is freely diffusible in the cytosol [including virtually all of the phosphorylated (p) Ankrd 2-Ser99 form], similar to 15% is bound to non-nuclear membranes, and similar to 15% is bound at cytoskeletal sites, likely at the N2A region of titin. These data are not consistent with the proposal that Ankrd 2, per se, or pAnkrd 2-Ser99 mediates stretch-induced signaling in skeletal muscle, dissociating from titin and translocating to the nucleus, because the majority of these forms of Ankrd 2 are already free in the cytosol. It will be necessary to show that the titin-associated Ankrd 2 is modified by stretch in some as-yet-unidentified way, distinct from the diffusible pool, if it is to act as a stretch-sensitive signaling molecule.