| First Author | Werneburg N | Year | 2004 |
| Journal | Am J Physiol Gastrointest Liver Physiol | Volume | 287 |
| Issue | 2 | Pages | G436-43 |
| PubMed ID | 15075251 | Mgi Jnum | J:95675 |
| Mgi Id | MGI:3526771 | Doi | 10.1152/ajpgi.00019.2004 |
| Citation | Werneburg N, et al. (2004) TNF-alpha-mediated lysosomal permeabilization is FAN and caspase 8/Bid dependent. Am J Physiol Gastrointest Liver Physiol 287(2):G436-43 |
| abstractText | TNF-alpha cytotoxic signaling involves lysosomal permeabilization with release of the lysosomal protease cathepsin B (ctsb) into the cytosol. However, the mechanisms mediating lysosomal breakdown remain unclear. Because caspase-8 and factor associated with neutral sphingomyelinase activation (FAN) have been implicated as proximal mediators of TNF-alpha-associated apoptosis, their role in lysosomal permeabilization was examined. Cellular distribution of ctsb-green fluorescent protein (ctsb-GFP) in a rat hepatoma cell line was imaged by confocal microscopy. ctsb-GFP fluorescence was punctate under basal conditions but became diffuse after treatment with TNF-alpha/actinomycin D. This cellular redistribution of ctsb-GFP was blocked by transfection with a vector expressing a dominant-negative Fas-associated protein with death domain (DeltaFADD), cytokine response modifier A, or a pharmacological caspase-8 inhibitor, IETD-fmk. Consistent with the concept that caspase 8-mediated apoptosis is also Bid-dependent in hepatocytes, ctsb-GFP release from lysosomes was reduced in hepatocytes from Bid(-/-) mice. Interestingly, transfection with a vector expressing a dominant-negative FAN (DeltaFAN) also blocked ctsb-GFP release and caspase-8 activation. Paradigms that inhibited ctsb-GFP release from lysosomes also reduced apoptosis as assessed by morphology and biochemical criteria. In conclusion, these studies suggest FAN is upstream of caspase-8/Bid in a signaling cascade culminating in lysosomal permeabilization. |
