Role of BNIP3 in TNF-induced cell death - TNF upregulates BNIP3 expression

• Tumor necrosis factor alpha (TNF) is a cytokine that induces caspase-dependent (apoptotic) and caspase-independent (necrosis-like) cell death in different cells. We used the murine fibrosarcoma cell line model L929 and a stable L929 transfectant over-expressing a mutated dominant-negative form of BNIP3 lacking the C-terminal transmembrane (TM) domain (L929-ΔTM-BNIP3) to test if TNF-induced cell death involved pro-apoptotic Bcl2 protein BNIP3. Treatment of cells with TNF in the absence of actinomycin D caused a rapid fall in the mitochondrial membrane potential (Δ Ψ m ) and a prompt increase in reactive oxygen species (ROS) production, which was significantly less pronounced in L929-ΔTM-BNIP3. TNF did not cause the mitochondrial release of apoptosis inducing factor (AIF) and Endonuclease G (Endo-G) but provoked the release of cytochrome c , Smac/Diablo, and Omi/HtrA2 at similar levels in both L929 and in L929-ΔTM-BNIP3 cells. We observed TNF-associated increase in the expression of BNIP3 in L929 that was mediated by nitric oxide and significantly inhibited by nitric oxide synthase inhibitor N 5 -(methylamidino)-l-ornithine acetate. In L929, lysosomal swelling and activation were markedly increased as compared to L929-ΔTM-BNIP3 and could be inhibited by treatment with inhibitors to vacuolar H + -ATPase and cathepsins −B/−L. Together, these data indicate that TNF-induced cell death involves BNIP3, ROS production, and activation of the lysosomal death pathway.

Ämnesord

Natural Sciences  (hsv)

Biological Sciences  (hsv)

Biochemistry and Molecular Biology  (hsv)

Naturvetenskap  (hsv)

Biologiska vetenskaper  (hsv)

Biokemi och molekylärbiologi  (hsv)

Cell Biology  (hsv)

Cellbiologi  (hsv)

Nyckelord

Caspase; Cathepsin; Flow cytometry; Lysosome; ROS