FLIP protects against hypoxia/reoxygenation-induced endothelial cell apoptosis by inhibiting Bax activation.

Abstract

Hypoxia/reoxygenation causes cell death, yet the underlying regulatory mechanisms remain partially understood. Recent studies demonstrate that hypoxia/reoxygenation can activate death receptor and mitochondria-dependent apoptotic pathways, involving Bid and Bax mitochondrial translocation and cytochrome c release. Using mouse lung endothelial cells (MLEC), we examined the role of FLIP, an inhibitor of caspase 8, in hypoxia/reoxygenation-induced cell death. FLIP protected MLEC against hypoxia/reoxygenation by blocking both caspase 8/Bid and Bax/mitochondrial apoptotic pathways. FLIP inhibited Bax activation in wild-type and Bid(-/-) MLEC, indicating independence from the caspase 8/Bid pathway. FLIP also inhibited the expression and activation of protein kinase C (PKC) (alpha, zeta) during hypoxia/reoxygenation and promoted an association of inactive forms of PKC with Bax. Surprisingly, FLIP expression also inhibited death-inducing signal complex (DISC) formation in the plasma membrane and promoted the accumulation of the DISC in the Golgi apparatus. FLIP expression also upregulated Bcl-X(L), an antiapoptotic protein. In conclusion, FLIP decreased DISC formation in the plasma membrane by blocking its translocation from the Golgi apparatus and inhibited Bax activation through a novel PKC-dependent mechanism. The inhibitory effects of FLIP on Bax activation and plasma membrane DISC formation may play significant roles in protecting endothelial cells from the lethal effects of hypoxia/reoxygenation.

• Authors: Xue Wang, Yong Wang, Jinglan Zhang, Hong Pyo Kim, Stefan W Ryter, Augustine M K Choi
• Journal: Molecular and cellular biology (Mol Cell Biol) Vol. 25 Issue 11 Pg. 4742-51 (Jun 2005) ISSN: 0270-7306 [Print] United States
• PMID: 15899875 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• BAX protein, human
• BH3 Interacting Domain Death Agonist Protein
• BID protein, human
• Bax protein, mouse
• Bid protein, mouse
• CASP8 and FADD-Like Apoptosis Regulating Protein
• CFLAR protein, human
• Carrier Proteins
• Caspase Inhibitors
• Cflar protein, mouse
• Death Domain Receptor Signaling Adaptor Proteins
• Intracellular Signaling Peptides and Proteins
• Proto-Oncogene Proteins c-bcl-2
• Receptors, Tumor Necrosis Factor
• bcl-2-Associated X Protein
• Protein Kinase C
• CASP8 protein, human
• Casp8 protein, mouse
• Caspase 8
• Caspases

Topics

• Animals
• Apoptosis
• BH3 Interacting Domain Death Agonist Protein
• CASP8 and FADD-Like Apoptosis Regulating Protein
• Carrier Proteins (antagonists & inhibitors, metabolism)
• Caspase 8
• Caspase Inhibitors
• Caspases (metabolism)
• Cell Hypoxia
• Cell Membrane (metabolism)
• Death Domain Receptor Signaling Adaptor Proteins
• Endothelial Cells (metabolism)
• Humans
• Intracellular Signaling Peptides and Proteins (genetics, metabolism)
• Lung (cytology)
• Mice
• Protein Kinase C (metabolism)
• Protein Transport
• Proto-Oncogene Proteins c-bcl-2 (antagonists & inhibitors, metabolism)
• Receptors, Tumor Necrosis Factor (metabolism)
• bcl-2-Associated X Protein