Notch1 antiapoptotic activity is abrogated by caspase cleavage in dying T lymphocytes.
Excessive signaling via the Notch1 receptor inhibits apoptosis in T lymphocytes. Since several antiapoptotic proteins are cleaved by caspases during cell death, we investigated whether Notch1 was a caspase substrate. Results demonstrate that the intracellular domain of Notch1 (NICD) is cleaved into six fragments during apoptosis in Jurkat cells or peripheral T lymphocytes. Notch1 cleavage is prevented by the caspase inhibitors DEVD-fmk and VEID-fmk or by Bcl-2 expression. Caspase-3 and caspase-6 cleave the NICD into six fragments using sites located within the NF-kappaB binding domain, the ankyrin repeats and the transactivation domain. Notch1 cleavage correlates with the loss of HES-1 expression in apoptotic T cells. Notch1 fragments cannot inhibit activation-induced cell death in a T-cell hybridoma, confirming the abrogation of Notch1 antiapoptotic activity by caspases. The ability of the NICD but not the fragments to antagonize Nur77 activity supports a role for this factor in Notch1 antiapoptotic function.
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Laboratoire d'Immunologie, CR-CHUM, campus St-Luc, Pavillon Edouard-Asselin, 264 Bd. René Lévesque E., Montréal, Québec, Canada H2X 1P1. luchino.cohen@umontreal.ca
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D000595:Amino Acid Sequence; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D051792:Basic Helix-Loop-Helix Proteins; D053148:Caspase 3; D053178:Caspase 6; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D002460:Cell Line; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors; D018398:Homeodomain Proteins / Q000096:biosynthesis; D006801:Humans; D006825:Hybridomas; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000378:metabolism; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D017434:Protein Structure, Tertiary; D051881:Receptor, Notch1; D011956:Receptors, Cell Surface / Q000502:physiology*; D018160:Receptors, Cytoplasmic and Nuclear / Q000037:antagonists & inhibitors; D011987:Receptors, Steroid / Q000037:antagonists & inhibitors; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism*; D000072056:Transcription Factor HES-1; D051996:Transcription Factor RelA; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000502:physiology*
D051792:Basic Helix-Loop-Helix Proteins; D053148:Caspase 3; D053178:Caspase 6; D061945:Caspase Inhibitors; D020169:Caspases; D015853:Cysteine Proteinase Inhibitors; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D016328:NF-kappa B; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D051881:Receptor, Notch1; D011956:Receptors, Cell Surface; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; D000072056:Transcription Factor HES-1; D051996:Transcription Factor RelA; D014157:Transcription Factors; C497761:NOTCH1 protein, human; C539821:NR4A1 protein, human; C078493:HES1 protein, human; C505407:CASP3 protein, human; C505514:CASP6 protein, human