**1. Introduction**

Destruxin A (DA, Figure 1A) isolated from entomopathogenic fungus *Metarhizium anisopliae* is a cyclodepsipeptidic mycotoxin with insecticidal, antifeedant, and anti-immunity effects on host insects [1,2]. It is also reported that DA is a key pathogenic factor of *M. anisopliae* against insects [3]. DA is considered as a new potential pesticide to contract researchers interesting. For this, it is necessary to elucidate the targets of DA acting on insects. In the past decade, several studies indicated that DA changes the morphology of hemocytes and brings on equilibrium chaos of intra- and extra- cellular hydrogen and calcium ion in *Bombyx mori* [4,5], and regulates immune related gene expression [6,7]. Recently, a few DA binding-proteins in silkworm were found [8–10]. However, these results are not enough to explain the mechanisms of DA against insects.

**Figure 1.** Profiles of interaction between Destruxin A (DA) with BmArgRS, BmLamin-C and BmPRP1 (**A**) The structure of Destruxin A. (**B**) BLI analysis showed the interactions of DA with BmArgRS and BmLamin-C but not BmPRP1 in vitro. (**C**) Cellular thermal shift assay (CETSA) results showed the interations of DA with BmArgRS and BmLamin-C in vivo.

To discover the DA target molecules, we conducted experiments based on drug affinity responsive target stability (DARTS) [11] in Bm12 cells; nuclear membranes protein Lamin-C (BmLamin-C), arginine tRNA synthetase (BmArgRS), and ATP-dependent RNA helicase PRP1 (BmPRP1) were detected. These three proteins have been studied thoroughly in human and model organisms to date. Summarily, Lamin-C belongs to nuclear intermediate filament proteins which provides mechanical stability, organizes chromatin and regulates transcription and other nuclear activities [12]. Moreover, recent studies have shown that Lamin-C plays role in development, tissue responsing to mechanical, reactive oxygen species, and thermal stresses [7]. ArgRS is significant in protein synthesis process, which provides arginine and maintaining fidelity in peptide chain extension [13,14]. While PRP1 has the functions of pre-mRNA-splicing and its fidelity of recognition [14,15]. However, these proteins have been rarely studied in *B. mori* and related biological pathways were never associated with DA target research before. In this study, we will validate the interaction of DA with these proteins in vivo and vitro. The results will provide new insights on better understanding for the DA-binding proteins.
