Destruxin A Induces and Binds HSPs in <i>Bombyx mori</i> Bm12 Cells

Destruxin A (DA) is a cyclodepsipeptidic mycotoxin isolated from the entomopathogenic fungus, <i>Metarhizium anisopliae</i>. It has insecticidal activity against host insect’s innate immunity system, but the molecular mechanism is not yet elucidated. In our previous experiment, four HSPs (heat shock proteins, BmHSP70–3, BmHSP75, BmHSP83, and BmHSCP) were characterized from the specific protein electrophoretic bands of <i>Bombyx mori</i> Bm12 cell line treated with DA in the test of drug affinity responsive target stability (DARTS), which implied that these HSPs might be kinds of DA-affinity proteins, or DA induces them up-regulated expression. Therefore, in current research, the interactions of DA and HSPs were explored through analysis of bio-layer interferometry (BLI) employing FortBio OcteteQK. The expression levels of HSPs genes were surveyed by quantitative real-time polymerase chain reaction (qPCR). The results indicated that DA had no interactions with BmHSP70–3, BmHSP75, and BmHSP83, but had affinity to BmHSCP with a <i>K</i><sub>D</sub> value of 88.1 μM, in BLI analysis. However, the expression levels of all HSPs genes were significantly up-regulated after the Bm12 cells were treated by DA. In conclusion, DA can induce the four HSPs expression in Bm12 cells, but DA only binds to BmHSCP. Our research provides new insights on understanding of the action mechanisms of destruxins.