Ikezoe Koji, Furuya Hirokazu, Ohyagi Yasumasa, Osoegawa Manabu, Nishino Ichizo, Nonaka Ikuya, Kira Jun-Ichi
Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University 60, 812-8582, Fukuoka, Japan.
Acta Neuropathol. 2003 Jun;105(6):603-9. doi: 10.1007/s00401-003-0686-1. Epub 2003 Mar 8.
Dysferlin is a newly identified sarcolemmal protein related to Miyoshi myopathy and limb-girdle muscular dystrophy. Although its function is still unknown, it is inferred from the presence of C2 domains and a transmembrane domain in its sequence that dysferlin may be expressed or located not only at the sarcolemma but also in other membranous organelles to interact with Ca(2+). Tubular aggregates (TAs) are derived from sarcoplasmic reticulum (SR) and found in various myopathies, especially in those related to disturbed intra-sarcoplasmic Ca(2+) homeostasis. To clarify the expression of dysferlin in TAs and the relationship among TA formation, dysferlin expression, and endoplasmic reticulum (ER) stress, we examined the expression of dysferlin and other sarcolemmal proteins by immunohistochemistry in 12 muscle biopsy specimens with TAs from 11 cases of periodic paralysis and 1 case of myalgia/cramps syndrome. Moreover, the expression of glucose-regulated protein 78 (GRP78) and GRP94, which are up-regulated under ER stress, was also examined by immunohistochemistry and immunoblotting. TAs showed strong expression of dysferlin. GRP78 and GRP94 were also intensely expressed in TAs. Total amounts of GRP78 and GRP94 were significantly increased in muscles with TAs compared with normal controls. These results indicate that muscles with TAs seem to be under ER stress, probably resulting from disturbed intra-sarcoplasmic Ca(2+) homeostasis. Strong expression of dysferlin in TAs suggests the possibility that it is located not only at the sarcolemma but also in the SR, at least in the pathological conditions.
dysferlin是一种新发现的肌膜蛋白，与宫下肌病和肢带型肌营养不良相关。尽管其功能尚不清楚，但从其序列中存在C2结构域和跨膜结构域可推断，dysferlin可能不仅在肌膜表达或定位，还存在于其他膜性细胞器中以与Ca(2+)相互作用。管状聚集物（TAs）源自肌浆网（SR），在各种肌病中均可发现，尤其是那些与肌浆内Ca(2+)稳态紊乱相关的肌病。为了阐明dysferlin在TAs中的表达以及TA形成、dysferlin表达和内质网（ER）应激之间的关系，我们通过免疫组织化学检测了12例来自11例周期性瘫痪和1例肌痛/痉挛综合征患者的带有TAs的肌肉活检标本中dysferlin和其他肌膜蛋白的表达。此外，还通过免疫组织化学和免疫印迹检测了在ER应激下上调的葡萄糖调节蛋白78（GRP78）和GRP94的表达。TAs显示dysferlin强表达。GRP78和GRP94在TAs中也强烈表达。与正常对照相比，带有TAs的肌肉中GRP78和GRP94的总量显著增加。这些结果表明，带有TAs的肌肉似乎处于ER应激状态，这可能是由肌浆内Ca(2+)稳态紊乱所致。dysferlin在TAs中的强表达提示，至少在病理条件下，它不仅位于肌膜，还位于SR。
