Shrestha Sony, Park Jiyeong, Ahn Seung-Joon, Kim Yonggyun
Department of Bioresource Sciences, Andong National University, Andong, Korea.
Department of Entomology, Pennsylvania State University, University Park, Pennsylvania.
Arch Insect Biochem Physiol. 2015 Aug;89(4):218-29. doi: 10.1002/arch.21238. Epub 2015 Apr 6.
Prostaglandin E2 (PGE2 ) mediates immune responses of the beet armyworm, Spodoptera exigua, including oenocytoid cell lysis (a class of lepidopteran hemocytes: OCL) via its specific membrane receptor to release inactive prophenoloxidase (PPO) into hemolymph. PPO is activated into phenoloxidase in the plasma to play crucial roles in the immune responses of S. exigua. The mechanism of OCL has not been elucidated, however we posed the hypothesis that a rapid accumulation of sodium ions within the oenocytoids allows a massive influx of water by the ion gradient, which leads to the cell lysis. It remains unclear which sodium channel is responsible for the OCL in response to PGE2 . This study identified a specific sodium channel called sodium-potassium-chloride cotransporter 1 (Se-NKCC1) expressed in hemocytes of S. exigua and analyzed its function in the OCL in response to PGE2 . Se-NKCC1 encodes a basic membrane protein (pI value = 8.445) of 1,066 amino acid residues, which contains 12 putative transmembrane domains. Se-NKCC1 was expressed in all developmental stages and tissues. qPCR showed that bacterial challenge significantly induced its expression. A specific inhibitor of NKCC, bumetanide, prevented the OCL in a dose-dependent manner. When RNA interference (RNAi) using double-stranded RNA specific to Se-NKCC1 suppressed its expression, the OCL and PPO activation were significantly inhibited in response to PGE2 . The RNAi treatment also reduced nodule formation to bacterial challenge. These results suggest that Se-NKCC1 is associated with OCL by facilitating inward transport of ions in response to PGE2 .
前列腺素E2（PGE2）介导甜菜夜蛾（Spodoptera exigua）的免疫反应，包括通过其特定的膜受体介导oenocytoid细胞裂解（一类鳞翅目血细胞：OCL），从而将无活性的酚氧化酶原（PPO）释放到血淋巴中。PPO在血浆中被激活为酚氧化酶，在甜菜夜蛾的免疫反应中发挥关键作用。然而，OCL的机制尚未阐明，我们提出了一个假设，即oenocytoids内钠离子的快速积累通过离子梯度允许大量水分涌入，从而导致细胞裂解。目前尚不清楚哪种钠通道负责响应PGE2的OCL。本研究鉴定了一种在甜菜夜蛾血细胞中表达的特定钠通道，称为钠-钾-氯共转运蛋白1（Se-NKCC1），并分析了其在响应PGE2的OCL中的功能。Se-NKCC1编码一种由1066个氨基酸残基组成的碱性膜蛋白（pI值=8.445），其中包含12个假定的跨膜结构域。Se-NKCC1在所有发育阶段和组织中均有表达。qPCR显示细菌攻击显著诱导其表达。NKCC的特异性抑制剂布美他尼以剂量依赖的方式阻止了OCL。当使用针对Se-NKCC1的双链RNA进行RNA干扰（RNAi）抑制其表达时，响应PGE2的OCL和PPO激活被显著抑制。RNAi处理还减少了对细菌攻击的结节形成。这些结果表明，Se-NKCC1通过促进响应PGE2的离子内向转运与OCL相关。
