Hepat Rahul, Kim Yonggyun
Department of Bioresource Sciences, Andong National University, Andong 760-749, Republic of Korea.
Department of Bioresource Sciences, Andong National University, Andong 760-749, Republic of Korea.
J Insect Physiol. 2014 Apr;63:40-7. doi: 10.1016/j.jinsphys.2014.02.008. Epub 2014 Mar 4.
Juvenile hormone (JH) regulates diverse physiological processes in insects during entire developmental stages. Especially, the identification of Methoprene-tolerant (Met), a JH nuclear receptor, allows us to better understand molecular actions of JH to control gene expressions related with metamorphosis. However, several physiological processes including cellular immune response and some molecular actions of JH have been suspected to be mediated via its non-genomic actions. To prove its non-genomic action, JH nuclear signals were suppressed by RNA interference (RNAi) of Met or its downstream gene, Krüppel homolog 1 (Kr-h1), in the red flour beetle, Tribolium castaneum. These RNAi-treated larvae failed to undergo a normal development and suffered precocious metamorphosis. Hemocytes of T. castaneum exhibited their spreading behavior on extracellular matrix and nodule formation in response to bacterial challenge. When the larvae were treated with either RNAi of Met or Kr-h1, the hemocytes of the treated larvae were responsive to JH without any significant difference with those of control larvae. These results suggest that the response of hemocytes to JH is not mediated by its nuclear signal. On the other hand, the JH modulation of hemocyte behaviors of T. castaneum was significantly influenced by membrane and cytosolic protein activities, in which ethoxyzolamide (a specific inhibitor of carbonic anhydrase), calphostin C (a specific inhibitor of protein kinase C) or ouabain (a specific inhibitor of Na(+)-K(+) ATPase) significantly suppressed the responsiveness of hemocytes to JH.
保幼激素（JH）在昆虫的整个发育阶段调节多种生理过程。特别是，耐甲氧普烯（Met）作为一种JH核受体的鉴定，使我们能够更好地理解JH控制与变态相关基因表达的分子作用。然而，包括细胞免疫反应和JH的一些分子作用在内的几个生理过程被怀疑是通过其非基因组作用介导的。为了证明其非基因组作用，在赤拟谷盗（Tribolium castaneum）中，通过对Met或其下游基因Krüppel同源物1（Kr-h1）进行RNA干扰（RNAi）来抑制JH核信号。这些经RNAi处理的幼虫未能正常发育，并出现早熟变态。赤拟谷盗的血细胞在受到细菌攻击时，会在细胞外基质上表现出铺展行为并形成结节。当用Met或Kr-h1的RNAi处理幼虫时，处理后幼虫的血细胞对JH有反应，与对照幼虫的血细胞没有显著差异。这些结果表明，血细胞对JH的反应不是由其核信号介导的。另一方面，赤拟谷盗血细胞行为的JH调节受到膜和胞质蛋白活性的显著影响，其中乙氧唑胺（碳酸酐酶的特异性抑制剂）、钙磷蛋白C（蛋白激酶C的特异性抑制剂）或哇巴因（Na(+)-K(+) ATP酶的特异性抑制剂）显著抑制了血细胞对JH的反应性。
