Truncated RIP3 (tRIP3) acts upstream of FADD to induce apoptosis in the human hepatocellular carcinoma cell line QGY-7703.
RIP3 (receptor-interacting protein 3) is a serine/threonine kinase that promotes apoptosis in various cell types. The C-terminal domain of RIP3 is critical for its apoptosis induction. In this study, we showed that a truncated form of RIP3 (tRIP3) containing only the unique C-terminal region (aa 224-518) induced significant apoptosis in human hepatocellular carcinoma cells QGY-7703. A FADD-dominant negative (FADD-DN) was shown to significantly block apoptosis induced by tRIP3. In contrast, the RIP3 dominant negative (RIP3-DN) was found unable to block FADD-induced apoptosis. Thus, we conclude that tRIP3 may function upstream of FADD to induce apoptosis in TNFR-1 signaling pathway. Additionally, sequence alignments of RIP3 with other death domain (DD)-containing proteins revealed that amino acids Leu 477 and Leu 488 in RIP3 are highly conserved, nonetheless, neither mutational change at Leu 477 nor at Leu 488 confers obvious effect on cell death, indicating that these two amino acids might not be critical for its pro-apoptotic activity as expected.
Feng
Shanshan
S
Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Anhui, People's Republic of China.
Ma
Li
L
Yang
Yonghui
Y
Wu
Mian
M
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000235:genetics / Q000378:metabolism; D017209:Apoptosis; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D045744:Cell Line, Tumor; D053200:Fas-Associated Death Domain Protein; D006801:Humans; D007930:Leucine / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D011494:Protein Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D053422:Receptor-Interacting Protein Serine-Threonine Kinases; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction
D048868:Adaptor Proteins, Signal Transducing; D000596:Amino Acids; C505533:FADD protein, human; D053200:Fas-Associated Death Domain Protein; D011494:Protein Kinases; C119705:RIPK3 protein, human; D053422:Receptor-Interacting Protein Serine-Threonine Kinases; D007930:Leucine