An 86 amino acids motif in CAPN3 is essential for formation of the nucleolus-localized Def-CAPN3 complex

• Published in: Biochemical and biophysical research communications Vol. 623; pp. 66 - 73
• Main Authors: Ding, Feng, Huang, Delai, Wang, Mingyun, Peng, Jinrong
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01-10-2022
• Subjects: CAPN3 (Calpain3); Def (Digestive-organ expansion factor); Human; Nucleolus; Utp25; Zebrafish; Utp25; Human; Def (Digestive-organ expansion factor); Zebrafish; Nucleolus; CAPN3 (Calpain3)
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2022.06.032

Digestive-organ expansion factor (Def) is a nucleolar protein that recruits cysteine proteinase Calpain3 (CAPN3) into the nucleolus to form the Def-CAPN3 complex in both human and zebrafish. This complex mediates the degradation of the tumor suppressor p53 and ribosome biogenesis factor mitotic phosphorylated protein 10 (Mpp10) in nucleolus, demonstrating the importance of this complex in regulating cell cycle and ribosome biogenesis. However, the Def and CAPN3 interacting motifs have yet been identified. In this report, by using a series of truncated or internally deleted human CAPN3 (hCAPN3) derivatives we identify that an essential motif of 86 amino acids (86-aa) (430-515aa) in hCAPN3 for its interaction with human Def (hDef), and this 86-aa motif is highly conserved in zebrafish Capn3b (zCapn3b) and is also required for the interaction between zebrafish Def (zDef) and zCapn3b. We further identify the 2/3 C-terminus of hDef is responsible for mediating the hDef-hCAPN3 interaction, and the corresponding region is conserved for the zDef and zCapn3b interaction. Our results lay the ground to resolve the structure of the Def-CAPN3 complex in the future.
•Human hDef and hCAPN3 full length proteins form a complex.•An 86-aa motif between 430 and 515aa in hCAPN3 is required for its interaction with hDef.•The 86-aa motif is conserved in zebrafish zCapn3b and is required for its interaction with zDef.•The 2/3 C-terminus of hDef interacts with hCAPN3.•A large portion of the C-terminus of zDef interacts with zCapn3b.