ATP11C, a member of the P4-ATPase family, translocates phosphatidylserine and phosphatidylethanolamine at the plasma membrane. We previously revealed that its C-terminal splice variant ATP11C-b exhibits polarized localization in motile cell lines, such as MDA-MB-231 and Ba/F3. In the present study, we found that the C-terminal cytoplasmic region of ATP11C-b interacts specifically with ezrin. Notably, the LLxY motif in the ATP11C-b C-terminal region is crucial for its interaction with ezrin as well as its polarized localization on the plasma membrane. A constitutively active, C-terminal phosphomimetic mutant of ezrin was colocalized with ATP11C-b in polarized motile cells. ATP11C-b was partially mislocalized in cells depleted of ezrin alone, and exhibited greater mislocalization in cells simultaneously depleted of the family members ezrin, radixin and moesin (ERM), suggesting that ERM proteins, particularly ezrin, contribute to the polarized localization of ATP11C-b. Furthermore, Atp11c knockout resulted in C-terminally phosphorylated ERM protein mislocalization, which was restored by exogenous expression of ATP11C-b but not ATP11C-a. These observations together indicate that the polarized localizations of ATP11C-b and the active form of ezrin to the plasma membrane are interdependently stabilized.

中文翻译：

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ATP11C-b 与 ezrin 的相互作用有助于其极化定位。

ATP11C 是 P4-ATPase 家族的成员，在质膜上转运磷脂酰丝氨酸和磷脂酰乙醇胺。我们之前揭示了其 C 端剪接变体 ATP11C-b 在运动细胞系中表现出极化定位，例如 MDA-MB-231 和 Ba/F3。在本研究中，我们发现 ATP11C-b 的 C 端细胞质区域与 ezrin 特异性相互作用。值得注意的是，ATP11C-b C 端区域中的 LLxY 基序对其与 ezrin 的相互作用及其在质膜上的极化定位至关重要。ezrin 的组成型活性 C 末端拟磷突变体与极化运动细胞中的 ATP11C-b 共定位。ATP11C-b 在单独耗尽 ezrin 的细胞中部分错误定位，并且在同时耗尽家族成员 ezrin 的细胞中表现出更大的错误定位，radixin and moesin (ERM)，表明 ERM 蛋白，尤其是埃兹蛋白，有助于 ATP11C-b 的极化定位。此外，敲除 Atp11c 导致 C 末端磷酸化的 ERM 蛋白错误定位，这可以通过外源表达 ATP11C-b 而不是 ATP11C-a 恢复。这些观察结果共同表明，ATP11C-b 的极化定位和 ezrin 的活性形式在质膜上相互稳定。