Cytotoxicity-dependent APO-1 (Fas/CD95)-associated proteins form a death-inducing signaling complex (DISC) with the receptor.
APO-1 (Fas/CD95), a member of the tumor necrosis factor receptor superfamily, induces apoptosis upon receptor oligomerization. In a search to identify intracellular signaling molecules coupling to oligomerized APO-1, several cytotoxicity-dependent APO-1-associated proteins (CAP) were immunoprecipitated from the apoptosis-sensitive human leukemic T cell line HUT78 and the lymphoblastoid B cell line SKW6.4. CAP1-3 (27-29 kDa) and CAP4 (55 kDa), instantly detectable after the crosslinking of APO-1, were associated only with aggregated (the signaling form of APO-1) and not with monomeric APO-1. CAP1 and CAP2 were identified as serine phosphorylated MORT1/FADD. The association of CAP1-4 with APO-1 was not observed with C-terminally truncated non-signaling APO-1. In addition, CAP1 and CAP2 did not associate with an APO-1 cytoplasmic tail carrying the lprcg amino acid replacement. Moreover, no APO-1-CAP association was found in the APO-1+, anti-APO-1-resistant pre-B cell line Boe. Our data suggest that in vivo CAP1-4 are the APO-1 apoptosis-transducing molecules.
Tumor Immunology Program, German Cancer Center, Heidelberg, Germany.
F C
FC
Kischkel
S
S
Hellbardt
I
I
Behrmann
M
M
Germer
M
M
Pawlita
P H
PH
Krammer
M E
ME
Peter
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D001483:Base Sequence; D002352:Carrier Proteins / Q000378:metabolism / Q000502:physiology*; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D002460:Cell Line; D003432:Cross-Linking Reagents; D003546:Cysteine Endopeptidases / Q000378:metabolism; D017931:DNA Primers; D053200:Fas-Associated Death Domain Protein; D006801:Humans; D008214:Lymphocytes / Q000502:physiology; D008969:Molecular Sequence Data; D010766:Phosphorylation; D014407:Tumor Cells, Cultured; D019014:fas Receptor / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D003432:Cross-Linking Reagents; D017931:DNA Primers; C505533:FADD protein, human; D053200:Fas-Associated Death Domain Protein; D019014:fas Receptor; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D003546:Cysteine Endopeptidases