title: Sphingolipid metabolism cooperates with BAK and BAX to promote the mitochondrial pathway of apoptosis.
abstract: Mitochondria are functionally and physically associated with heterotypic membranes, yet little is known about how these interactions impact mitochondrial outer-membrane permeabilization (MOMP) and apoptosis. We observed that dissociation of heterotypic membranes from mitochondria inhibited BAK/BAX-dependent cytochrome c (cyto c) release. Biochemical purification of neutral sphingomyelinases that correlated with MOMP sensitization suggested that sphingolipid metabolism coordinates BAK/BAX activation. Using purified lipids and enzymes, sensitivity to MOMP was achieved by in vitro reconstitution of the sphingolipid metabolic pathway. Sphingolipid metabolism inhibitors blocked MOMP from heavy membrane preparations but failed to influence MOMP in the presence of sphingolipid-reconstituted, purified mitochondria. Furthermore, the sphingolipid products, sphingosine-1-PO(4) and hexadecenal, cooperated specifically with BAK and BAX, respectively. Sphingolipid metabolism was also required for cellular responses to apoptosis. Our studies suggest that BAK/BAX activation and apoptosis are coordinated through BH3-only proteins and a specific lipid milieu that is maintained by heterotypic membrane-mitochondrial interactions.
authors.affiliation: Mount Sinai School of Medicine, Department of Oncological Sciences, New York, NY 10029, USA. jerry.chipuk@mssm.edu
authors.forename: Jerry E
authors.initials: JE
authors.lastname: Chipuk
authors.forename: Gavin P
authors.initials: GP
authors.lastname: McStay
authors.forename: Archana
authors.initials: A
authors.lastname: Bharti
authors.forename: Tomomi
authors.initials: T
authors.lastname: Kuwana
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Clarke
authors.forename: Leah J
authors.initials: LJ
authors.lastname: Siskind
authors.forename: Lina M
authors.initials: LM
authors.lastname: Obeid
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Green
mesh_terms: D000818:Animals; D017209:Apoptosis; D005260:Female; D006367:HeLa Cells; D006801:Humans; D008099:Liver / Q000166:cytology; D053858:Metabolic Networks and Pathways; D051379:Mice; D008810:Mice, Inbred C57BL; D008928:Mitochondria / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism; D013107:Sphingolipids / Q000378:metabolism*; D013108:Sphingomyelin Phosphodiesterase / Q000378:metabolism; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000378:metabolism*; D051028:bcl-2-Associated X Protein / Q000378:metabolism*
chemical_list: C494773:Bak1 protein, mouse; C494827:Bax protein, mouse; D013107:Sphingolipids; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D013108:Sphingomyelin Phosphodiesterase