Changes in FADD levels, distribution, and phosphorylation in TNFalpha-induced apoptosis in hepatocytes is caspase-3, caspase-8 and BID dependent.
FADD/MORT1 (The adaptor protein of Fas Associate Death Domain/Mediator of Receptor Induced Toxicity) is essential for signal transduction of death receptor signaling. We have previously shown that FADD is significantly up-regulated in TNFalpha/ActD induced apoptosis. Over-expression of FADD also induces death of lung cancer cells and primary hepatocytes. We hypothesize that the increase in detectable FADD levels require the proximal steps in apoptotic signaling and speculated that FADD would be redistributed in cells destined to undergo apoptosis. We show that monomeric non-phosphorylated FADD is up-regulated in hepatocytes treated with TNFalpha/ActD and that it accumulates in the cytoplasm. Nuclear phosphorylated FADD decreases with TNFalpha/ActD treatment. Dimeric FADD in the cytoplasm remains constant with TNFalpha/ActD. The change in FADD levels and distribution was dependent on caspase-3, caspase-8 activity and the presence of BID. Thus, changes in FADD levels and distribution are downstream of caspase activation and mitochondria changes that are initiated by the formation of the DISC complex. Changes in FADD levels and distribution may represent a novel feed-forward mechanism to propagate apoptosis signaling in hepatocytes.
Department of Surgery, University of Pittsburgh, School of Medicine, Pittsburgh, PA 15213, USA.
Xiaoying
X
Zhang
Raghuveer
R
Vallabhaneni
Patricia A
PA
Loughran
Richard
R
Shapiro
Xiao-Min
XM
Yin
Youzhong
Y
Yuan
Timothy R
TR
Billiar
D021581:Active Transport, Cell Nucleus / Q000187:drug effects / Q000502:physiology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D051023:BH3 Interacting Domain Death Agonist Protein / Q000187:drug effects / Q000378:metabolism*; D053148:Caspase 3 / Q000187:drug effects / Q000378:metabolism; D053181:Caspase 8 / Q000187:drug effects / Q000378:metabolism; D020169:Caspases / Q000187:drug effects / Q000378:metabolism*; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism; D003609:Dactinomycin / Q000494:pharmacology; D053418:Death Domain Receptor Signaling Adaptor Proteins / Q000187:drug effects / Q000378:metabolism; D053200:Fas-Associated Death Domain Protein / Q000187:drug effects / Q000378:metabolism*; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D008297:Male; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010766:Phosphorylation / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000187:drug effects / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
D051023:BH3 Interacting Domain Death Agonist Protein; C494815:Bid protein, mouse; D053418:Death Domain Receptor Signaling Adaptor Proteins; C505534:Fadd protein, mouse; D053200:Fas-Associated Death Domain Protein; D014409:Tumor Necrosis Factor-alpha; D003609:Dactinomycin; C505409:Casp3 protein, mouse; D053148:Caspase 3; D053181:Caspase 8; D020169:Caspases