Dictyostelium cells cope with hypo‐osmotic stress with a contractile vacuole (CV) system, which consists of one or two vacuoles that cyclically charge and discharge. Uniquely, a F‐Actin remodeling dependent minimal mixing of the CV membrane components with the target plasmalemma during the fusion and the dischargement warrants the integrity of the CV bladder for an efficient next CV cycle. The effect of hypo‐osmotic stress on F‐Actin remodeling activity, however, is currently not well understood. Dictyostelium cells increase the level of intracellular superoxide level in response to hypo‐osmotic stress, which in turn activates redox‐sensitive Ras proteins, but not Akt, which is one of the Ras downstream targets and a major regulator of F‐Actin remodeling. However, Akt is not insulated from the active Ras in cells lacking Superoxide dismutase C (SodC). We report here that sodC^‐ cells were compromised in the CV structure and function and the attenuation of Ras/PI3K/Akt signaling in several independent means significantly improved the compromised CV structure but not the function. Interestingly, when sodC^‐ cells were treated with 5‐(N,N‐Dimethyl) amiloride hydrochloride (EIPA), an inhibitor of sodium proton exchanger (NHE), both the structure and the function of the CV improved. Thus, a proper CV biogenesis in sodC^‐ cells was insufficient to restore their CV function, which in turn indicates the presence of an additional target for SodC and EIPA that modulates CV function.

中文翻译：

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超氧化物歧化酶 C 影响网柄菌收缩液泡的生物发生和功能

网柄细胞通过收缩液泡 (CV) 系统应对低渗压力，该系统由一个或两个循环充电和放电的液泡组成。独特的是，在融合和放电过程中，CV 膜成分与目标质膜的 F-肌动蛋白重塑依赖的最小混合保证了 CV 膀胱的完整性，以实现有效的下一个 CV 循环。然而，低渗压力对 F-肌动蛋白重塑活动的影响目前尚不清楚。盘基网柄菌细胞响应低渗压力增加细胞内超氧化物水平，这反过来激活氧化还原敏感的 Ras 蛋白，但不激活 Akt，后者是 Ras 下游靶标之一，也是 F-肌动蛋白重塑的主要调节剂。然而，在缺乏超氧化物歧化酶 C (SodC) 的细胞中，Akt 并未与活性 Ras 隔离。我们在此报告sodC ^-细胞的 CV 结构和功能受损，Ras/PI3K/Akt 信号的衰减以几种独立的方式显着改善受损的 CV 结构，但没有改善功能。有趣的是，当sodC ^-细胞用 5-( N , N‐Dimethyl)amiloride hydrochloride (EIPA)，钠质子交换剂 (NHE) 的抑制剂，改善了 CV 的结构和功能。因此，在一个适当的CV生物合成SODC ^-细胞不足以恢复其CV功能，这又指示另外的目标为SODC存在和EIPA该调制CV功能。