A humoral factor, hemolymph proteinase 8, elicits a cellular defense response of nodule formation in Bombyx mori larvae in association with recognition by C-type lectins. (July 2021)

• Record Type: Journal Article
• Authors: Tokunaga, Kotomi; Tezuka, Moeko; Tang, Shuyi; Shu, Min; Yamagishi, Takayuki; Sato, Ryoichi
• Is Part Of: Journal of insect physiology. Volume 132(2021)
• Publication Date: 2021-07
• Subjects: Nodule -- Hemolymph protease -- Humoral immune factor -- Cellular immune system -- Degranulation -- Hemocytin -- PAMPs recognition receptor -- C-type lectin -- Spätzle -- Insect; BmLBP B. mori lipopolysaccharide binding protein -- BmMBP B. mori multiple binding protein -- PAR protease-activated receptor -- PAMPs pathogen-associated molecular patterns -- HP hemolymph protease -- SPH serine protease homologue; Insects -- Physiology -- Periodicals; Insectes -- Physiologie -- Périodiques; Insects -- Physiology; Periodicals; 571.157
• DOI: 10.1016/j.jinsphys.2021.104252
• Languages: English
• ISSNs: 0022-1910

Abstract

Graphical abstract: Highlights: BmHP8 is a nodule formation-eliciting hemolymph protease. BmHP8 elicits nodule formation against both bacteria and fungi on these cells. Nodule formation-eliciting PAMPs-recognition proteins are BmLBP and BmMBP. Abstract: Previously, we found that nodule formation, a cellular defense response in insects, is regulated by humoral factors called C-type lectins in the hemolymph. To elucidate the factors that elicit nodule formation following the recognition of microorganisms by C-type lectins, a reproducible quantitative in vitro assay system was constructed. Then, using this system, the inhibitory activities of antisera raised against hemolymph proteases (HPs), serine protease homologues (SPHs), and pathogen-associated molecular pattern (PAMP)-recognition proteins were assessed. Among the antisera raised against HP and SPH, only that against HP8, a terminal proteinase that activates Spätzle, consistently inhibited in-vitro nodule-like aggregate formation in all three tested microorganisms, Micrococcus luteus, Escherichia coli, and Saccharomyces cerevisiae . Antisera raised against C-type lectins, BmLBP, and BmMBP also inhibited nodule-like aggregate formation, while those against β-glucan recognition proteins and peptidoglycan recognition protein-S1 did not. Microorganisms pretreated with hemolymph, which contains HP8 and C-type lectins, also induced nodule-like aggregate formation, indicating that nodulation factors are present on microbial cells. Furthermore, antisera raised against HP8, BmLBP, and BmMBP showed inhibitory activities in the in vivo nodule formation system using Bombyx mori larvae. Thus, two humoral factors in the hemolymph of B . mori larvae, BmHP8 and C-type lectins, were found to play significant roles in eliciting the cellular defense response of nodule formation.