Blockade of tumor necrosis factor-induced Bid cleavage by caspase-resistant Rb.
Tumor necrosis factor-alpha (TNF) activates caspase-8 to cleave effector caspases or Bid, resulting in type-1 or type-2 apoptosis, respectively. We show here that TNF also induces caspase-8-dependent C-terminal cleavage of the retinoblastoma protein (Rb). Interestingly, fibroblasts from Rb(MI/MI) mice, in which the C-terminal caspase cleavage site is mutated, exhibit a defect in Bid cleavage despite caspase-8 activation. Recent results suggest that TNF receptor endocytosis is required for the activation of caspase-8. Consistent with this notion, inhibition of V-ATPase, which plays an essential role in acidification and degradation of endosomes, specifically restores Bid cleavage in Rb(MI/MI) cells. Inhibition of V-ATPase sensitizes Rb(MI/MI) but not wild-type fibroblasts to TNF-induced apoptosis and stimulates inflammation-associated colonic apoptosis in Rb(MI/MI) but not wild-type mice. These results suggest that Rb cleavage is required for Bid cleavage in TNF-induced type-2 apoptosis, and this requirement can be supplanted by the inhibition of V-ATPase.
Division of Biological Sciences, Department of Medicine, University of California, San Diego, La Jolla, California 92093-0820, USA.
XiaoDong
X
Huang
Anja
A
Masselli
Steven M
SM
Frisch
Irina C
IC
Hunton
Yong
Y
Jiang
Jean Y J
JY
Wang
D000818:Animals; D017209:Apoptosis; D051023:BH3 Interacting Domain Death Agonist Protein / Q000378:metabolism*; D001665:Binding Sites; D053181:Caspase 8 / Q000378:metabolism; D020169:Caspases / Q000378:metabolism*; D045304:Cytochromes c / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D051379:Mice; D017434:Protein Structure, Tertiary; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors / Q000378:metabolism*; D025262:Vacuolar Proton-Translocating ATPases / Q000378:metabolism
D051023:BH3 Interacting Domain Death Agonist Protein; D047888:Receptors, Tumor Necrosis Factor, Type I; D016160:Retinoblastoma Protein; D014409:Tumor Necrosis Factor-alpha; D045304:Cytochromes c; D053181:Caspase 8; D020169:Caspases; D025262:Vacuolar Proton-Translocating ATPases