Reply to "Letter to the editor: Comments on Wette et al. (2017): 'Characterization of muscle ankyrin repeat proteins in human skeletal muscle'".
نویسندگان
چکیده
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 ~3.1 µmol/kg, much greater than DARP and CARP (~0.11 and ~0.02 µmol/kg, respectively). All DARP was found to be tightly bound at cytoskeletal (or possibly nuclear) sites. In contrast, ~70% of the total Ankrd 2 is freely diffusible in the cytosol [including virtually all of the phosphorylated (p)Ankrd 2-Ser99 form], ~15% is bound to non-nuclear membranes, and ~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.
منابع مشابه
Letter to the editor: Comments on Wette et al. (2017): "Characterization of muscle ankyrin repeat proteins in human skeletal muscle".
TO THE EDITOR: In their recent paper, Wette et al. (4) describe the distribution of muscle ankyrin repeat proteins, i.e., Ankrd 1, Ankrd 2, and Ankrd 3, in muscle cells (4). One of the aims of the authors is to understand if Ankrd 2 and its phosphorylated form at serine 99 (pAnkrd 2-Ser99) redistribute from titin to the nucleus following a prolonged stretch stress. Although the authors have tri...
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عنوان ژورنال:
- American journal of physiology. Cell physiology
دوره 313 3 شماره
صفحات -
تاریخ انتشار 2017