Institute of Biophysics, Consiglio Nazionale delle Ricerche, Via de Marini 6, 16149, Genova, Italy.
Cell Mol Life Sci. 2018 May;75(9):1657-1670. doi: 10.1007/s00018-017-2704-9. Epub 2017 Nov 9.
Mutations in the human TMEM16E (ANO5) gene are associated both with the bone disease gnathodiaphyseal dysplasia (GDD; OMIM: 166260) and muscle dystrophies (OMIM: 611307, 613319). However, the physiological function of TMEM16E has remained unclear. We show here that human TMEM16E, when overexpressed in mammalian cell lines, displayed partial plasma membrane localization and gave rise to phospholipid scrambling (PLS) as well as non-selective ionic currents with slow time-dependent activation at highly depolarized membrane potentials. While the activity of wild-type TMEM16E depended on elevated cytosolic Ca levels, a mutant form carrying the GDD-causing T513I substitution showed PLS and large time-dependent ion currents even at low cytosolic Ca concentrations. Contrarily, mutation of the homologous position in the Ca-activated Cl channel TMEM16B paralog hardly affected its function. In summary, these data provide the first direct demonstration of Ca-dependent PLS activity for TMEM16E and suggest a gain-of-function phenotype related to a GDD mutation.
人类 TMEM16E（ANO5）基因突变与骨骼疾病颌骨-骨干发育不良（GDD；OMIM：166260）和肌肉萎缩症（OMIM：611307、613319）有关。然而，TMEM16E 的生理功能仍不清楚。我们在这里表明，在哺乳动物细胞系中过表达人类 TMEM16E 时，它显示出部分质膜定位，并导致磷脂翻转（PLS）以及在高度去极化膜电位下具有缓慢时间依赖性激活的非选择性离子电流。虽然野生型 TMEM16E 的活性取决于升高的细胞浆 Ca 水平，但携带 GDD 致病 T513I 取代的突变形式即使在低细胞浆 Ca 浓度下也显示出 PLS 和大的时间依赖性离子电流。相反，在钙激活氯离子通道 TMEM16B 同源位置的突变几乎不影响其功能。总之，这些数据首次直接证明了 TMEM16E 的 Ca 依赖性 PLS 活性，并提示与 GDD 突变相关的功能获得表型。
