title: Lysosomal ceramide generated by acid sphingomyelinase triggers cytosolic cathepsin B-mediated degradation of X-linked inhibitor of apoptosis protein in natural killer/T lymphoma cell apoptosis.
abstract: We previously reported that IL-2 deprivation induced acid sphingomyelinase-mediated (ASM-mediated) ceramide elevation and apoptosis in an NK/T lymphoma cell line KHYG-1. However, the molecular mechanism of ASM-ceramide-mediated apoptosis during IL-2 deprivation is poorly understood. Here, we showed that IL-2 deprivation induces caspase-dependent apoptosis characterized by phosphatidylserine externalization, caspase-8, -9, and -3 cleavage, and degradation of X-linked inhibitor of apoptosis protein (XIAP). IL-2 re-supplementation rescued apoptosis via inhibition of XIAP degradation without affecting caspase cleavage. However, IL-2 deprivation induced ceramide elevation via ASM in lysosomes and activated lysosomal cathepsin B (CTSB) but not cathepsin D. A CTSB inhibitor CA-074 Me and knockdown of CTSB inhibited ceramide-mediated XIAP degradation and apoptosis. Inhibition of ceramide accumulation in lysosomes using an ASM inhibitor, desipramine, decreased cytosolic activation of CTSB by inhibiting its transfer into cytosol from the lysosome. Knockdown of ASM also inhibited XIAP degradation and apoptosis. Furthermore, cell permeable N-acetyl sphingosine (C2-ceramide), which increases mainly endogenous d18:1/16:0 and d18:1/24:1 ceramide-like IL-2 deprivation, induced caspase-dependent apoptosis with XIAP degradation through CTSB. These findings suggest that lysosomal ceramide produced by ASM mediates XIAP degradation by activation of cytosolic CTSB and caspase-dependent apoptosis. The ASM-ceramide-CTSB signaling axis is a novel pathway of ceramide-mediated apoptosis in IL-2-deprived NK/T lymphoma cells.
authors: Department of Life Science, Medical Research Institute, Kanazawa Medical University, 1-1 Daigaku, Uchinada, Ishikawa 920-0293, Japan.
authors: M
authors: 0000000159208285
authors: M
authors: Taniguchi
authors: Division of Hematology/Immunology, Department of Medicine, Kanazawa Medical University, 1-1 Daigaku Uchinada, Uchinada, Ishikawa 920-0293, Japan.
authors: H
authors: H
authors: Ogiso
authors: Division of Hematology/Immunology, Department of Medicine, Kanazawa Medical University, 1-1 Daigaku Uchinada, Uchinada, Ishikawa 920-0293, Japan.
authors: T
authors: T
authors: Takeuchi
authors: Department of Biobank, Tohoku Medical Megabank Organization, Tohoku University, 1-1 Seiryo, Aoba, Sendai 980-8574, Japan.
authors: K
authors: K
authors: Kitatani
authors: Department of Rheumatology and Clinical Immunology, Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan.
authors: H
authors: H
authors: Umehara
authors: Division of Hematology/Immunology, Department of Medicine, Kanazawa Medical University, 1-1 Daigaku Uchinada, Uchinada, Ishikawa 920-0293, Japan.
authors: T
authors: T
authors: Okazaki
mesh_terms: D017209:Apoptosis / Q000502:physiology; D053148:Caspase 3 / Q000378:metabolism; D002401:Cathepsin B / Q000378:metabolism*; D045744:Cell Line, Tumor; D002518:Ceramides / Q000096:biosynthesis* / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D006801:Humans; D007376:Interleukin-2 / Q000172:deficiency / Q000378:metabolism; D007694:Killer Cells, Natural / Q000378:metabolism / Q000473:pathology*; D016399:Lymphoma, T-Cell / Q000378:metabolism / Q000473:pathology*; D008247:Lysosomes / Q000378:metabolism; D013108:Sphingomyelin Phosphodiesterase / Q000378:metabolism*; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000378:metabolism*
chemical_list: D002518:Ceramides; D007376:Interleukin-2; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; D013108:Sphingomyelin Phosphodiesterase; D053148:Caspase 3; C533912:CTSB protein, human; D002401:Cathepsin B