CTL10 has multiple functions in the innate immune responses of the silkworm, Bombyx mori

Insect C-type lectins (CTLs) play crucial roles in modulating the humoral and cellular immune responses. In the domesticated silkworm Bombyx mori L., BmCTL10 gene encodes an immulectin containing two carbohydrate recognition domains (CRDs). The phylogenetic analysis showed that BmCTL10 didn't cluster with other immulectin homologs in B. mori. BmCTL10 was mainly expressed in second to fifth instar larvae, wandering stage larvae, prepupa, and adults. In naive fifth instar larvae, BmCTL10 was predominantly expressed in the fat body and epidermis. In second instar larvae, the topical application of Beauveria bassiana by immersion caused down regulation of BmCTL10. The intra-hemocoel injection of E. coli, S. aureus, B. bassiana, and 20-hydroxyecdysone in fifth instar larvae caused tissue and time-specific inductions. The recombinant protein (rBmCTL10) can bind to larval hemocytes and various pathogen-associated molecular patterns to enhance hemocyte-mediated nodulation, phagocytosis, and encapsulation. rBmCTL10 caused significant upregulation of most antimicrobial peptides and nitric oxide synthase 1 in hemocytes in vivo. Yeast two-hybrid demonstrated that integrin133 and134 subunits can interact with BmCTL10. Furthermore, only CRD2 can interact with the 133, while both CRD1 and CRD2 can interact with the 134. Taken together, this study showed that BmCTL10 has multiple functions in the innate immune responses of B. mori and two integrin 13 subunits are their potential receptors.

Automated summary

Insect C-type lectins, with BmCTL10 being a representative example, play important roles in regulating immune responses in Bombyx mori. BmCTL10 is mainly expressed in larvae and adults, and has the ability to enhance hemocyte-mediated nodulation, phagocytosis, and encapsulation through interactions with various pathogen-associated molecular patterns. The study also suggests that integrin 133 and 134 subunits may serve as potential receptors for BmCTL10 in immune responses.