Mitsuhashi Wataru, Shimura Sachiko, Miyamoto Kazuhisa, Sugimoto Takafumi N
Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, Tsukuba, Ibaraki, 305-8634, Japan.
Arch Virol. 2019 Jan;164(1):17-25. doi: 10.1007/s00705-018-4013-5. Epub 2018 Sep 17.
Oral inoculation of entomopoxvirus spindles, microstructures composed of fusolin protein, causes disruption of the peritrophic matrix (PM), a physical barrier against microbe infection, in the insect midgut. Although the atomic structure of fusolin has been determined, little has been directly elucidated of the mechanism of disruption of the PM. In the present study, we first performed an immunohistochemical examination to determine whether fusolin acts on the PM directly or indirectly in the midgut of Bombyx mori larvae that were inoculated with spindles of Anomala cuprea entomopoxvirus. This revealed that the PM, rather than the midgut cells, was the attachment site for fusolin. Fusolin broadly attached to the PM from the anterior to the posterior region, both to its ectoperitrophic and endoperitrophic surfaces and within the PM. These results likely explain why the whole of the PM is rapidly disintegrated. Second, we administered protease inhibitors mixed with spindles and observed decreased midgut protease activity and reduced disruption of the PM. This suggests that midgut protease(s) is also positively involved in PM disruption. Based on the present results, we propose an overall mechanism for the disruption of the PM by administration of fusolin.
经口接种昆虫痘病毒纺锤体（一种由梭林蛋白构成的微观结构）会导致昆虫中肠的围食膜（一种抵御微生物感染的物理屏障）遭到破坏。尽管梭林的原子结构已被确定，但围食膜破坏机制的直接阐述却很少。在本研究中，我们首先进行了免疫组织化学检查，以确定梭林在接种了铜绿丽金龟昆虫痘病毒纺锤体的家蚕幼虫中肠内是直接还是间接作用于围食膜。结果表明，围食膜而非中肠细胞是梭林的附着位点。梭林广泛地附着于围食膜，从前部到后部区域，附着于围食膜的外表面和内表面以及围食膜内部。这些结果可能解释了为什么整个围食膜会迅速解体。其次，我们将蛋白酶抑制剂与纺锤体混合给药，观察到中肠蛋白酶活性降低且围食膜破坏减少。这表明中肠蛋白酶也积极参与围食膜的破坏。基于目前的结果，我们提出了梭林给药导致围食膜破坏的总体机制。
