title: Regulation of alternative splicing of caspase-2 through an intracellular signaling pathway in response to pro-apoptotic stimuli.
abstract: Alternative splicing is an important mechanism in the generation of functionally distinct products from the same gene. Some apoptosis-regulating genes also undergo alternative splicing, generating splice variants that antagonzie normal transcripts on apoptosis. For example, caspase-2 is alternatively spliced, leading to exon 9-lacking caspase-2L (proapoptotic) and exon 9-containing caspase-2S (antiapoptotic) transcripts. Serine-arginine splicing factor proteins (SR proteins) are highly conserved and required for constitutive and alternative messenger RNA (mRNA) splicing. Their activity is regulated by reversible phosphorylation on serine residue. During apoptosis, many functional molecules undergo posttranslational modification, including phosphorylation, dephosphorylation, and caspase cleavage. In this study, we investigated the effect of proapoptotic stimuli on alternative splicing of caspase-2 mRNA in U937 cells. U937 cells were simulated with etoposide, staurosporine, pacritaxel, or cyclohexamide. We analzyed the alternative splicing of caspase-2 mRNA using reverse transcription-polymerase chain reaction. Etoposide, staurosporine, pacritaxel, and cyclohexamide treatment promoted exon-9 inclusion, increasing the ratio of caspase-2S to caspase-2L in a time-dependent manner. Pretreatment with calyculin A, an inhibitor of protein phosphatase-1, blocked etoposide-induced alternative splicing of caspase-2 mRNA. Furthermore, pretreatment of U937 cells with fumonisin B1, an inhibitor of ceramide synthase, also blocked alternative splicing of caspase-2 mRNA. These data demonstrate that endogenous ceramide generation and subsequent phosphatase activation during apoptosis are key steps in the alternative splicing of caspase-2 mRNA and further suggest a link between the signal-transduction pathway and alternative splicing.
authors.affiliation: First Department of Internal Medicine, Graduate School of Biomedical Science, Nagasaki University, Nagasaki, Japan.
authors.forename: Nozomi
authors.initials: N
authors.lastname: Iwanaga
authors.forename: Makoto
authors.initials: M
authors.lastname: Kamachi
authors.forename: Kouichiro
authors.initials: K
authors.lastname: Aratake
authors.forename: Yasumori
authors.initials: Y
authors.lastname: Izumi
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Ida
authors.forename: Fumiko
authors.initials: F
authors.lastname: Tanaka
authors.forename: Mami
authors.initials: M
authors.lastname: Tamai
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Arima
authors.forename: Hideki
authors.initials: H
authors.lastname: Nakamura
authors.forename: Tomoki
authors.initials: T
authors.lastname: Origuchi
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kawakami
authors.forename: Katsumi
authors.initials: K
authors.lastname: Eguchi
mesh_terms: D017398:Alternative Splicing / Q000502:physiology*; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D053143:Caspase 2; D020169:Caspases / Q000235:genetics*; D002518:Ceramides / Q000096:biosynthesis / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005047:Etoposide / Q000494:pharmacology; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D007700:Kinetics; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D019311:Staurosporine / Q000494:pharmacology; D020298:U937 Cells; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D002518:Ceramides; D004791:Enzyme Inhibitors; D019384:Nucleic Acid Synthesis Inhibitors; D012333:RNA, Messenger; D005047:Etoposide; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D010744:Phosphoric Monoester Hydrolases; D053143:Caspase 2; D020169:Caspases; D019311:Staurosporine