Upstream of Growth and Differentiation Factor 1 (uog1), a Mammalian Homolog of the Yeast Longevity Assurance Gene 1 (LAG1), RegulatesN-Stearoyl-sphinganine (C18-(Dihydro)ceramide) Synthesis in a…

By Krishnan Venkataraman, C. Riebeling, J. Bodennec, Howard Riezman, J. Allegood, M. Sullards, Alfred H. Merrill Jr., A. Futerman. 2002

287 citations recorded by the source corpus.

The longevity assurance gene (LAG1) and its homolog (LAC1) are required for acyl-CoA-dependent synthesis of ceramides containing very long acyl chain (e.g. C26) fatty acids in yeast, and a homolog of LAG1, ASC1, confers resistance in plants to fumonisin B1, an inhibitor of ceramide synthesis. To understand further the mechanism of regulation of ceramide synthesis, we now characterize a mammalian homolog of LAG1,upstream of growth and differentiation factor-1 (uog1). cDNA clones of uog1 were obtained from expression sequence-tagged clones and sub-cloned into a mammalian expression vector. Transient transfection of human embryonic kidney 293T cells with uog1 followed by metabolic labeling with [4,5-3H]sphinganine orl-3-[3H]serine demonstrated thatuog1 conferred fumonisin B1 resistance with respect to the ability of the cells to continue to produce ceramide. Surprisingly, this ceramide was channeled into neutral glycosphingolipids but not into gangliosides. Electrospray tandem mass spectrometry confirmed the elevation in sphingolipids and revealed that the ceramides and neutral glycosphingolipids ofuog1-transfected cells contain primarily stearic acid (C18), that this enrichment was further increased by FB1, and that the amount of stearic acid in sphingomyelin was also increased. UOG1 was localized to the endoplasmic reticulum, demonstrating that the fatty acid selectivity and the fumonisin B1 resistance are not due to a subcellular localization different from that found previously for ceramide synthase activity. Furthermore, in vitro assays ofuog1-transfected cells demonstrated elevated ceramide synthase activity when stearoyl-CoA but not palmitoyl-CoA was used as substrate. We propose a role for UOG1 in regulating C18-ceramide (N-stearoyl-sphinganine) synthesis, and we note that not only is this the first case of ceramide formation in mammalian cells with such a high degree of fatty acid specificity, but also that theN-stearoyl-sphinganine produced by UOG1 most significantly impacts neutral glycosphingolipid synthesis.

Subfields: Biochemistry, Molecular Biology, Physiology

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Citations in the corpus

Mammalian Ceramide Synthases (2010, background): “The subcellular location of the CerS proteins is the ER (8, 10, 11, 20, 23, 26, 27), although it should be emphasized that Table 1 Comparison of human CerS”
Role of human longevity assurance gene 1 and C18-ceramide in chemotherapy-induced cell death in human head and neck squamous cell carcinomas (2007, methodology): “stearoyl- or palmitoyl CoA into [(3)H]dihydro-sphingosine for the generation of C18- or C16-ceramides, respectively, as described previously (17).”
Ceramide synthase 6 modulates TRAIL sensitivity and nuclear translocation of active caspase 3 in colon cancer cells (2009, unknown): “…A uthor M anuscript Exogenous CerS6 localizes primarily to the perinuclear region Ceramide synthases have been identified as proteins that localize to the endoplasmic reticulum (Kitatani et al., 2006; Mizutani et al., 2005; Riebeling et al., 2003; Senkal et al., 2007; Venkataraman et al., 2002).”
Molecular machinery for non-vesicular trafficking of ceramide (2003, methodology): “In support of the latter possibility, overexpression of the uog1 gene in human embryonic kidney 293T cells results in an upregulation of de novo synthesis of C 18 ceramide, but not of C 16 ceramide, and the C 18 ceramide synthesized is preferentially used for the synthesis of GlcCe”
An overview of sphingolipid metabolism: from synthesis to breakdown (2010, background): “For example, CerS1 has been shown to prefer stearoyl CoA as a substrate and mainly produces C18-ceramide species [20].”
Lip1p: a novel subunit of acyl‐CoA ceramide synthase (2005, background): “Since human homologs of LAC1 and LAG1 have been recently isolated and can complement the lac1 and lag1 mutations (Venkataraman et al, 2002; Guillas et al, 2003; Riebeling et al, 2003), it would be surprising if no functional homologs of Lip1p were found.”
The complex life of simple sphingolipids (2004, background): “…of the same gene family, control which fatty acids are N-acylated to sphingoid bases to generate different ceramide species (Riebeling et al, 2003; Venkataraman et al, 2002), and the tissue distribution of the expression of these genes implies that specific ceramides might have specific functions…”