biostudies-literatureLiu YJMinistry of Science and Technology of the People’s Republic of ChinaNational Natural Science Foundation of ChinaMinistry of Science and Technology of the People's Republic of China (Chinese Ministry of Science and Technology)National Natural Science Foundation of China (National Science Foundation of China)801-813https://www.ebi.ac.uk/biostudies/studies/S-EPMC8249557biostudies-literatureUnknown31(7)Cathepsin D (cathD) is traditionally regarded as a lysosomal protease that degrades substrates in acidic compartments. Here we report cathD plays an unconventional role as a cofilin phosphatase orchestrating actin remodeling. In neutral pH environments, the cathD precursor directly dephosphorylates and activates the actin-severing protein cofilin independent of its proteolytic activity, whereas mature cathD degrades cofilin in acidic pH conditions. During development, cathD complements the canonical cofilin phosphatase slingshot and regulates the morphogenesis of actin-based structures. Moreover, suppression of cathD phosphatase activity leads to defective actin organization and cytokinesis failure. Our findings identify cathD as a dual-function molecule, whose functional switch is regulatCell researchThe noncanonical role of the protease cathepsin D as a cofilin phosphatase.PMC8249557315011282016YFA05010008180133081761138044, 81971260Cheng DWu CWang XDDuan DGong ZZhang TLiu YJZhu LHo MSLou HDuan SWang XChen SfalseThe noncanonical role of the protease cathepsin D as a cofilin phosphatase.Cathepsin D (cathD) is traditionally regarded as a lysosomal protease that degrades substrates in acidic compartments. Here we report cathD plays an unconventional role as a cofilin phosphatase orchestrating actin remodeling. In neutral pH environments, the cathD precursor directly dephosphorylates and activates the actin-severing protein cofilin independent of its proteolytic activity, whereas mature cathD degrades cofilin in acidic pH conditions. During development, cathD complements the canonical cofilin phosphatase slingshot and regulates the morphogenesis of actin-based structures. Moreover, suppression of cathD phosphatase activity leads to defective actin organization and cytokinesis failure. Our findings identify cathD as a dual-function molecule, whose functional switch is regulat2021-01-01T00:00:00Z2021 Jul2026-05-08T04:40:33.141Z2026-04-07T23:35:06.837ZS-EPMC82495573351491410.1038/s41422-020-00454-w