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Title: Switch from type II to I Fas/CD95 death signaling on in vitro culturing of primary hepatocytes. Author: Walter D, Schmich K, Vogel S, Pick R, Kaufmann T, Hochmuth FC, Haber A, Neubert K, McNelly S, von Weizsäcker F, Merfort I, Maurer U, Strasser A, Borner C. Journal: Hepatology; 2008 Dec; 48(6):1942-53. PubMed ID: 19003879. Abstract: UNLABELLED: Fas/CD95-induced apoptosis of hepatocytes in vivo proceeds through the so-called type II pathway, requiring the proapoptotic BH3-only Bcl-2 family member Bid for mitochondrial death signaling. Consequently, Bid-deficient mice are protected from anti-Fas antibody injection induced fatal hepatitis. We report the unexpected finding that freshly isolated mouse hepatocytes, cultured on collagen or Matrigel, become independent of Bid for Fas-induced apoptosis, thereby switching death signaling from type II to type I. In such in vitro cultures, Fas ligand (FasL) activates caspase-3 without Bid cleavage, Bax/Bak activation or cytochrome c release, and neither Bid ablation nor Bcl-2 overexpression is protective. The type II to type I switch depends on extracellular matrix adhesion, as primary hepatocytes in suspension die in a Bid-dependent manner. Moreover, the switch is specific for FasL-induced apoptosis as collagen-plated Bid-deficient hepatocytes are protected from tumor necrosis factor alpha/actinomycin D (TNFalpha/ActD)-induced apoptosis. CONCLUSION: Our data suggest a selective crosstalk between extracellular matrix and Fas-mediated signaling that favors mitochondria-independent type I apoptosis induction.[Abstract] [Full Text] [Related] [New Search]