Cullin-4B E3 ubiquitin ligase mediates Apaf-1 ubiquitination to regulate caspase-9 activity

• Published in: PloS one Vol. 14; no. 7; p. e0219782
• Main Authors: Ohta, Eri, Itoh, Masanori, Ueda, Masashi, Hida, Yoko, Wang, Miao-Xing, Hayakawa-Ogura, Miki, Li, Shimo, Nishida, Emika, Ohta, Kazunori, Tana, Islam, Saiful, Nakagawa, Kiyomi, Sunayama, Tomomi, Chen, Huayue, Hirata, So, Endo, Masashi, Ohno, Yoya, Nakagawa, Toshiyuki
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 22-07-2019; Public Library of Science (PLoS)
• Subjects: Antineoplastic agents; Apaf-1 protein; Apoptosis; Apoptotic Protease-Activating Factor 1 - metabolism; Aprotinin; Bcl-x protein; bcl-X Protein - metabolism; Biology and Life Sciences; Brain; Cancer patients; Cancer treatment; Caspase; Caspase 9 - metabolism; Caspase-9; Caspases; Chemotherapy; Cullin; Cullin Proteins - metabolism; Cyclin-dependent kinases; Cytochrome; Cytosol; EDTA; Enzyme Activation - drug effects; Etoposide; Etoposide - pharmacology; Gene expression; Health aspects; HEK293 Cells; Humans; Immunoglobulins; Insects; Intellectual disabilities; Kinases; Leupeptins - pharmacology; Ligases; Lung cancer; Lung diseases; Medicine; Melanoma; Mutation; Neurobiology; Neurosciences; Non-small cell lung cancer; Non-small cell lung carcinoma; Nuclear transport; Physical Sciences; Proteases; Proteasomes; Protein Binding - drug effects; Proteins; Research and Analysis Methods; Small cell lung cancer; Translocation; Ubiquitin; Ubiquitin-protein ligase; Ubiquitination; Ubiquitination - drug effects; University graduates; Japan
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0219782

Apoptotic protease-activating factor 1 (Apaf-1) is a component of apoptosome, which regulates caspase-9 activity. In addition to apoptosis, Apaf-1 plays critical roles in the intra-S-phase checkpoint; therefore, impaired expression of Apaf-1 has been demonstrated in chemotherapy-resistant malignant melanoma and nuclear translocation of Apaf-1 has represented a favorable prognosis of patients with non-small cell lung cancer. In contrast, increased levels of Apaf-1 protein are observed in the brain in Huntington's disease. The regulation of Apaf-1 protein is not yet fully understood. In this study, we show that etoposide triggers the interaction of Apaf-1 with Cullin-4B, resulting in enhanced Apaf-1 ubiquitination. Ubiquitinated Apaf-1, which was degraded in healthy cells, binds p62 and forms aggregates in the cytosol. This complex of ubiquitinated Apaf-1 and p62 induces caspase-9 activation following MG132 treatment of HEK293T cells that stably express bcl-xl. These results show that ubiquitinated Apaf-1 may activate caspase-9 under conditions of proteasome impairment.