TPCA‐1 compound, inhibiting testis‐specific serine/threonine protein kinase 3 for potential male sterile in Bombyx mori

Abstract BACKGROUND Protein kinases are a type of transferase enzyme that catalyze the phosphorylation of protein substrates, including receptor proteins. Testis‐specific serine/threonine kinases (TSSKs) are a highly conserved group of protein kinases found in various organisms. They play an essential role in male reproduction by influencing sperm development and function. RESULTS In this study, we report on the characterization of BmTSSK3, a TSSK from the silkworm, Bombyx mori . We found that BmTSSK3 is specifically expressed in the testis and localized to the sperm flagella, particularly in the sperm tail cyst. Furthermore, we developed BmTSSK3 inhibitors through molecular docking and binding assays. Small molecules 5‐(4‐Fluorophenyl)‐2‐ureidothiophene‐3‐carboxamide (TPCA‐1) and Imidurea were identified to bind to BmTSSK3. Using site‐specific mutation technology, we identified amino acid residues R134 and S184 as crucial binding sites for small molecules. RNA interference assay and Western blot analysis showed that knockdown of BmTSSK3 significantly decreased histone 3 phosphorylation. To confirm the inhibitory effect of these small molecules, we treated silkworm testes with TPCA‐1 and observed a strong inhibitory effect. CONCLUSION TPCA‐1 is an inhibitor of BmTSSK3, which raises its potential as a future candidate for male sterility of the silkworm. Thus, this study may offer a novel strategy for sterile silkworms as well as insects. © 2024 Society of Chemical Industry.