title: Regulation of mitochondrial ceramide distribution by members of the BCL-2 family.
abstract: Apoptosis is an intricately regulated cellular process that proceeds through different cell type- and signal-dependent pathways. In the mitochondrial apoptotic program, mitochondrial outer membrane permeabilization by BCL-2 proteins leads to the release of apoptogenic factors, caspase activation, and cell death. In addition to protein components of the mitochondrial apoptotic machinery, an interesting role for lipids and lipid metabolism in BCL-2 family-regulated apoptosis is also emerging. We used a comparative lipidomics approach to uncover alterations in lipid profile in the absence of the proapoptotic proteins BAX and BAK in mouse embryonic fibroblasts (MEFs). We detected over 1,000 ions in these experiments and found changes in an ion with an m/z of 534.49. Structural elucidation of this ion through tandem mass spectrometry revealed that this molecule is a ceramide with a 16-carbon N-acyl chain and sphingadiene backbone (d18:2/16:0 ceramide). Targeted LC/MS analysis revealed elevated levels of additional sphingadiene-containing ceramides (d18:2-Cers) in BAX, BAK-double knockout MEFs. Elevated d18:2-Cers are also found in immortalized baby mouse kidney epithelial cells lacking BAX and BAK. These results support the existence of a distinct biochemical pathway for regulating ceramides with different backbone structures and suggest that sphingadiene-containing ceramides may have functions that are distinct from the more common sphingosine-containing species.
authors.affiliation: Clayton Foundation Laboratories for Peptide Biology, Helmsley Center for Genomic Medicine, Salk Institute for Biological Studies, San Diego, CA 92037.
authors.forename: Tejia
authors.initials: T
authors.lastname: Zhang
authors.affiliation: Department of Pediatric Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215.
authors.forename: Lauren
authors.initials: L
authors.lastname: Barclay
authors.affiliation: Department of Pediatric Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215 Dana-Farber Cancer Institute and Children's Hospital Boston, and Linde Program in Cancer Chemical Biology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215.
authors.forename: Loren D
authors.initials: LD
authors.lastname: Walensky
authors.affiliation: Clayton Foundation Laboratories for Peptide Biology, Helmsley Center for Genomic Medicine, Salk Institute for Biological Studies, San Diego, CA 92037.
authors.forename: Alan
authors.initials: A
authors.lastname: Saghatelian
mesh_terms: D000818:Animals; D002460:Cell Line; D002518:Ceramides / Q000737:chemistry / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D055786:Gene Knockout Techniques; D051379:Mice; D008928:Mitochondria / Q000378:metabolism*; D015854:Up-Regulation; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D051028:bcl-2-Associated X Protein / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*
chemical_list: D002518:Ceramides; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein
keywords: apoptosis; ceramides; lipidomics; mass spectrometry; sphingolipids