Cathepsins are involved in ovarian remodeling post-parturition in black rockfish (Sebastes schlegelii).

Cathepsins (CTS) family of lysosomal proteases is characterized by high expression and proteolytic activity across various species. Notably, cathepsin B (CTSB) and cathepsin L (CTSL) have been implicated in uterine remodeling, follicle atrophy, and granulosa cell apoptosis in various vertebrates. This study investigated the role of the CTS members in post-parturitional ovarian remodeling in ovoviviparous black rockfish (Sebastes schlegelii). We cloned the ctsb (993 bp, encoding 330 amino acids) and ctsl (1011 bp, encoding 336 amino acids) genes from black rockfish. Quantitative Real-time PCR (qPCR) analysis revealed widespread tissue distribution for both genes, with ctsb expression being significantly highest in the ovary and markedly upregulated during the parturition process. In contrast, ctsl exhibited low ovarian expression with no increasing trend. In situ hybridization (ISH) and immunohistochemistry (IHC) localized CTSB to the ovarian stromal periphery and specific oocytes. Functional studies using recombinant mature CTSB demonstrated its proteolytic activity on ovarian tissue, leading to a significant increase in arginine (Arg) content. Post-parturition supplementation with Arg notably restored serum nutritional levels. Furthermore, dual- luciferase assays identified functional binding sites for Estrogen Receptor 1 (ESR1) and Specificity Protein 1 (SP1) within the ctsb promoter, regulating its transcription. Collectively, our findings indicate that CTSB, a member of the CTS family, is likely involved in ovarian remodeling in black rockfish.