Integrin β3 plays a novel role in innate immunity in silkworm, Bombyx mori

Integrins are transmembrane receptors that play essential roles in many physiological and pathological processes through cell-to-cell and cell-to-extracellular matrix (ECM) interactions. In the current study, a 2653-bp full-length cDNA of a novel integrin beta subunit (designated Bmintegrin beta 3) was obtained from silkworm hemocytes. Bmintegrin beta 3 has the typical conserved structure of the integrin beta family. The qRT-PCR results showed that Bmintegrin beta 3 was specifically expressed in the hematological system and that its expression was significantly increased after challenge with different types of PAMPs and bacteria. The recombinant Bmintegrin beta 3 protein displayed increased aggregation with S. aureus, suggesting that Bmintegrin beta 3 might directly bind to PAMPs. Interestingly, Bmintegrin beta 3 knockdown promoted PPO1, PPO2, BAEE, SPH78, SPH125, and SPH127 expression and accelerated the melanization process. Unexpectedly, the expression of genes related to phagocytosis, the Toll pathway, and the IMD pathway was also up-regulated after Bmintegrin, beta 3 knockdown. Thus, Bmintegrin beta 3 might be a pattern recognition protein (PRP) for PAMPs and might directly bind to bacteria and enhance the phagocytosis activity of hemocytes. Moreover, Bmintegrin beta 3 and its ligand might negatively regulate the expression of immune related genes through an unknown mechanism. In summary, our studies provide new insights into the immune functions of Bmintegrin beta 3 from the silkworm, Bombyx mori. (C) 2017 Elsevier Ltd. All rights reserved.