Scavenger receptor is pattern-recognition receptor (PRR) that plays a crucial function in host defense against pathogens. Scavenger receptor C (SR-C) is present only in invertebrates and its function has not been studied in detail. In this study, an SR-C homologous gene from the silkworm, Bombyx mori, was identified and characterized. SR-C was largely expressed in hemocytes and Malpighian tubules, with continuous expression in hemocytes. The peak expression was observed in hemocytes during molting and wandering stages both at mRNA and protein levels. Furthermore, immunofluorescence demonstrated it to be mainly distributed in the cell membranes of hemocytes, including oenocytoids and granulocytes. The recombinant SR-C protein (rSR-C) could bind to different types of bacteria and pathogen-associated molecular patterns (PAMPs), with strong binding to gram-positive bacteria and Lys-type peptidoglycans. The overexpression of SR-C induced the expression of genes related to the Toll pathway and antibacterial peptides. While the knockdown of SR-C reduced the expression of AMPs and inhibited the Toll pathway, it impaired the bacterial clearance ability of silkworm larvae, thus decreasing silkworm larvae's survival rate. Altogether, SR-C is a PRR that protect silkworms against bacterial pathogens by enhancing the expression of AMPs expression via the Toll pathway in hemocytes.

清道夫受体是模式识别受体 (PRR)，在宿主防御病原体方面起着至关重要的作用。清道夫受体 C (SR-C) 仅存在于无脊椎动物中，其功能尚未得到详细研究。在这项研究中，家蚕 Bombyx mori的 SR-C 同源基因, 被鉴定和表征。SR-C主要在血细胞和马氏小管中表达，并在血细胞中持续表达。在 mRNA 和蛋白质水平的蜕皮和游荡阶段，在血细胞中观察到峰值表达。此外，免疫荧光表明它主要分布在血细胞的细胞膜中，包括卵形细胞和粒细胞。重组 SR-C 蛋白 (rSR-C) 可以与不同类型的细菌和病原体相关分子模式 (PAMP) 结合，对革兰氏阳性菌和赖氨酸型肽聚糖具有很强的结合力。SR-C 的过表达诱导了与 Toll 通路和抗菌肽相关的基因的表达。虽然 SR-C 的敲低降低了 AMPs 的表达并抑制了 Toll 通路，它会损害家蚕幼虫的细菌清除能力，从而降低家蚕幼虫的成活率。总之，SR-C 是一种 PRR，通过增强 AMPs 的表达来保护家蚕免受细菌病原体的侵害通过血细胞中的 Toll 途径。