ABSTRACT

Unregulated Ca²⁺ influx affects intracellular Ca²⁺ homoeostasis, which may lead to neuronal death. In Drosophila, following the activation of rhodopsin the TRP Ca²⁺ channel is open to mediate the light-dependent depolarization. A constitutively active TRP channel triggers the degeneration of Trp^P365 /+ photoreceptors. To explore retinal degeneration, we employed a multidisciplinary approach including live imaging using GFP tagged actin and arrestin 2. Importantly, we demonstrate that the major rhodopsin (Rh1) was greatly reduced before the onset of rhabdomere degeneration; a great reduction of Rh1 affects the maintenance of rhabdomere leading to degeneration of photoreceptors. Trp^P365 /+ also led to the up-regulation of CaMKII, which is beneficial as suppression of CaMKII accelerated retinal degeneration. We explored the regulation of TRP by investigating the genetic interaction between Trp^P365 /+ and mutants affecting the turnover of diacylglycerol (DAG). We show a loss of phospholipase C in norpA^P24 exhibited a great reduction of the DAG content delayed degeneration of Trp^P365 /+ photoreceptors. In contrast, knockdown or mutations in DAG lipase (InaE) that is accompanied by slightly reduced levels of most DAG but an increased level of DAG 34:1, exacerbated retinal degeneration of Trp^P365 /+. Together, our findings support the notion that DAG plays a role in regulating TRP. Interestingly, DAG lipase is likely required during photoreceptor development as Trp^P365 /+; inaE^N125 double mutants contained severely degenerated rhabdomeres.

摘要

不受调节的Ca ²⁺流入影响细胞内 Ca ²⁺稳态，这可能导致神经元死亡。在果蝇中，在视紫质激活后，TRP Ca ²⁺通道打开以介导光依赖性去极化。组成型活动的 TRP 通道触发Trp ^P365 /+ 光感受器的退化。为了探索视网膜变性，我们采用了一种多学科方法，包括使用 GFP 标记的肌动蛋白和抑制蛋白 2 进行实时成像。重要的是，我们证明了主要视紫红质 (Rh1) 在横纹肌变性开始之前大大减少；Rh1 的大量减少会影响横纹肌的维持，导致光感受器的退化。色氨酸^P365 /+ 还导致 CaMKII 的上调，这是有益的，因为抑制 CaMKII 加速了视网膜变性。我们通过研究Trp ^P365 /+ 和影响二酰基甘油 (DAG) 转换的突变体之间的遗传相互作用来探索 TRP 的调控。我们表明， norpA ^P24 中磷脂酶 C 的损失表现出 DAG 含量的大幅减少，延迟了Trp ^P365 /+ 光感受器的退化。相比之下，DAG 脂肪酶 (InaE) 的敲低或突变伴随着大多数 DAG 水平略微降低但 DAG 34:1 水平升高，加剧了Trp ^{P365 的}视网膜变性 /+。总之，我们的发现支持 DAG 在调节 TRP 中发挥作用的观点。有趣的是，在光感受器发育过程中可能需要 DAG 脂肪酶，如Trp ^P365 /+；inaE ^N125 双突变体含有严重退化的横纹肌。