Department of Cell Biology, Emory University School of Medicine, Atlanta, GA.
J Cell Biol. 2021 Mar 1;220(3). doi: 10.1083/jcb.202007059.
Mutations in ANO5 (TMEM16E) cause limb-girdle muscular dystrophy R12. Defective plasma membrane repair is a likely mechanism. Using myofibers from Ano5 knockout mice, we show that trafficking of several annexin proteins, which together form a cap at the site of injury, is altered upon loss of ANO5. Annexin A2 accumulates at the wound to nearly twice the level observed in WT fibers, while annexin A6 accumulation is substantially inhibited in the absence of ANO5. Appearance of annexins A1 and A5 at the cap is likewise diminished in the Ano5 knockout. These changes are correlated with an alteration in annexin repair cap fine structure and shedding of annexin-positive vesicles. We conclude that loss of annexin coordination during repair is disrupted in Ano5 knockout mice and underlies the defective repair phenotype. Although ANO5 is a phospholipid scramblase, abnormal repair is rescued by overexpression of a scramblase-defective ANO5 mutant, suggesting a novel, scramblase-independent role of ANO5 in repair.
ANO5（TMEM16E）突变导致肢带型肌营养不良症 R12。细胞膜修复缺陷可能是其发病机制。利用 Ano5 基因敲除小鼠的肌纤维，我们发现几种膜联蛋白（它们共同在损伤部位形成帽状结构）的运输在 ANO5 缺失时发生改变。Ano5 缺失时，膜联蛋白 A2 在伤口处的积累几乎是 WT 纤维的两倍，而膜联蛋白 A6 的积累则显著受到抑制。Ano5 敲除小鼠的膜联蛋白 A1 和 A5 在帽状结构处的出现也减少。这些变化与膜联蛋白修复帽状结构精细结构的改变以及膜联蛋白阳性囊泡的脱落有关。我们的结论是，在 Ano5 基因敲除小鼠中，修复过程中膜联蛋白的协调丧失，导致了修复缺陷表型。尽管 ANO5 是一种磷脂翻转酶，但通过过表达一种翻转酶缺陷的 ANO5 突变体可以挽救异常修复，这表明 ANO5 在修复中具有一种新型的、与翻转酶无关的作用。
