Kicking off sphingolipid biosynthesis: structures of the serine palmitoyltransferase complex

Complex sphingolipids are ‘built’ on highly bio-active backbones (sphingoid bases and ceramides) that can cause cell death when the amounts are elevated by turnover of complex sphingolipids, disruption of normal sphingolipid metabolism, or over-induction of sphingolipid biosynthesis de novo. Under normal conditions, it appears that the bioactive intermediates of this pathway (3-keto-sphinganine, sphinganine and ceramides) are kept at relatively low levels. Both the intrinsic activity of serine palmitoyltransferase (SPT) and the availability of its substrates (especially palmitoyl-CoA) can have toxic consequences for cells by increasing the production of cytotoxic intermediates. Recent work has also revealed that diverse agonists and stresses (cytokines, UV light, glucocorticoids, heat shock and toxic compounds) modulate SPT activity by induction of SPTLC2 gene transcription and/or post-translational modification. Mutation of the SPTLC1 component of SPT has also been shown to cause hereditary sensory neuropathy type I, possibly via aberrant oversynthesis of sphingolipids. Another key step of the pathway is the acylation of sphinganine (and sphingosine in the recycling pathway) by ceramide synthase, and up-regulation of this enzyme (or its inhibition to cause accumulation of sphinganine) can also be toxic for cells. Since it appears that most, if not all, tissues synthesize sphingolipids de novo, it may not be surprising that disruption of this pathway has been implicated in a wide spectrum of disease.

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Myriocin, a serine palmitoyltransferase inhibitor, alters regional brain neurotransmitter levels without concurrent inhibition of the brain sphingolipid biosynthesis in mice

Toxicology Letters ◽

10.1016/j.toxlet.2003.10.016 ◽

2004 ◽

Vol 147 (1) ◽

pp. 87-94 ◽

Cited By ~ 14

Author(s):

Marcin F. Osuchowski ◽

Victor J. Johnson ◽

Quanren He ◽

Raghubir P. Sharma

Keyword(s):

Serine Palmitoyltransferase ◽

Regional Brain ◽

Brain Neurotransmitter ◽

Sphingolipid Biosynthesis ◽

The Brain

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ORMDL/serine palmitoyltransferase stoichiometry determines effects of ORMDL3 expression on sphingolipid biosynthesis

The Journal of Lipid Research ◽

10.1194/jlr.m057539 ◽

2015 ◽

Vol 56 (4) ◽

pp. 898-908 ◽

Cited By ~ 32

Author(s):

Deanna Siow ◽

Manjula Sunkara ◽

Teresa M. Dunn ◽

Andrew J. Morris ◽

Binks Wattenberg

Keyword(s):

Serine Palmitoyltransferase ◽

Sphingolipid Biosynthesis

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Crassaostrea gigas Oyster Shell Extract Inhibits Lipogenesis via Suppression of Serine Palmitoyltransferase

Natural Product Communications ◽

10.1177/1934578x1501000236 ◽

2015 ◽

Vol 10 (2) ◽

pp. 1934578X1501000

Author(s):

Nguyen Khoi Song Tran ◽

Jeong Eun Kwon ◽

Se Chan Kang ◽

Soon-Mi Shim ◽

Tae-Sik Park

Keyword(s):

De Novo ◽

Preventive Measure ◽

Ethanol Extract ◽

Oyster Shell ◽

Lipid Lowering ◽

Metabolic Dysfunction ◽

Serine Palmitoyltransferase ◽

Lipogenic Gene Expression ◽

Cholesterol Levels ◽

Sphingolipid Biosynthesis

Oysters are widely consumed seafood, but their shells impose a serious environmental problem. To extend the utilization of oyster shell waste, we investigated the biological role of oyster shell extract. In this study, we verified that the ethanol extract of oyster shell (EOS) contains taurine and betaine, the major components of oyster body. EOS downregulated transcription of Sptlc1 and Sptlc2 mRNA, the subunits of serine palmitoyltransferase (SPT). Suppression of SPT subunits reduced sphinganine and sphingomyelin by inhibiting de novo sphingolipid biosynthesis. Inhibition of sphingomyelin biosynthesis resulted in downregulation of lipogenic gene expression such as ACC, FAS, SCD1, and DGAT2. Consistent with inhibition of lipogenesis, cellular triglyceride levels were diminished by EOS, but cholesterol levels were not altered. Taken together, these results suggest that EOS has a lipid-lowering effect and could be applied as either a therapeutic or preventive measure for metabolic dysfunction.

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Use of isotopically labeled substrates reveals kinetic differences between human and bacterial serine palmitoyltransferase

The Journal of Lipid Research ◽

10.1194/jlr.m089367 ◽

2019 ◽

Vol 60 (5) ◽

pp. 953-962 ◽

Cited By ~ 3

Author(s):

Peter J. Harrison ◽

Kenneth Gable ◽

Niranjanakumari Somashekarappa ◽

Van Kelly ◽

David J. Clarke ◽

...

Keyword(s):

In Vivo Studies ◽

Serine Palmitoyltransferase ◽

Biochemical Pathways ◽

Catalytic Mechanisms ◽

Catalyzed Reactions ◽

Enzyme Catalyzed Reactions ◽

The Impact ◽

Sphingolipid Biosynthesis

Isotope labels are frequently used tools to track metabolites through complex biochemical pathways and to discern the mechanisms of enzyme-catalyzed reactions. Isotopically labeled l-serine is often used to monitor the activity of the first enzyme in sphingolipid biosynthesis, serine palmitoyltransferase (SPT), as well as labeling downstream cellular metabolites. Intrigued by the effect that isotope labels may be having on SPT catalysis, we characterized the impact of different l-serine isotopologues on the catalytic activity of recombinant SPT isozymes from humans and the bacterium Sphingomonas paucimobilis. Our data show that S. paucimobilis SPT activity displays a clear isotope effect with [2,3,3-D]l-serine, whereas the human SPT isoform does not. This suggests that although both human and S. paucimobilis SPT catalyze the same chemical reaction, there may well be underlying subtle differences in their catalytic mechanisms. Our results suggest that it is the activating small subunits of human SPT that play a key role in these mechanistic variations. This study also highlights that it is important to consider the type and location of isotope labels on a substrate when they are to be used in in vitro and in vivo studies.

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Rescue of cell growth by sphingosine with disruption of lipid microdomain formation in Saccharomyces cerevisiae deficient in sphingolipid biosynthesis

Biochemical Journal ◽

10.1042/bj20051354 ◽

2006 ◽

Vol 394 (1) ◽

pp. 237-242 ◽

Cited By ~ 21

Author(s):

Motohiro Tani ◽

Akio Kihara ◽

Yasuyuki Igarashi

Keyword(s):

Saccharomyces Cerevisiae ◽

Cell Growth ◽

Serine Palmitoyltransferase ◽

Kinase Gene ◽

Yeast Saccharomyces Cerevisiae ◽

Long Chain Base ◽

Triton X ◽

Lipid Microdomain ◽

Sphingolipid Biosynthesis ◽

Complex Sphingolipids

In the yeast Saccharomyces cerevisiae, sphingolipids are essential for cell growth. Inactivation of sphingolipid biosynthesis, such as by disrupting the serine palmitoyltransferase gene (LCB2), is lethal, but cells can be rescued by supplying an exogenous LCB (long-chain base) like PHS (phytosphingosine) or DHS (dihydrosphingosine). In the present study, supplying SPH (sphingosine), an unnatural LCB for yeast, similarly rescued the Δlcb2 cells, but only when SPH 1-phosphate production was inhibited by deleting the LCB kinase gene LCB4. Exogenously added SPH was adequately converted into phosphoinositol-containing complex sphingolipids. Interestingly, cells carrying SPH-based sphingolipids exhibited a defect in the association of Pma1p with Triton X-100-insoluble membrane fractions, and displayed sensitivities to both Ca2+ and hygromycin B. These results suggest that the SPH-based sphingolipids in these cells have properties that differ from those of the PHS- or DHS-based sphingolipids in regard to lipid microdomain formation, leading to abnormal sensitivities towards certain environmental stresses. The present paper is the first report showing that in sphingolipid-deficient S. cerevisiae, the requirement for LCB can be fulfilled by exogenous SPH, although this supplement results in failure of lipid microdomain formation.

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Cell Cycle Progression and Cell Polarity Require Sphingolipid Biosynthesis in Aspergillus nidulans

Molecular and Cellular Biology ◽

10.1128/mcb.21.18.6198-6209.2001 ◽

2001 ◽

Vol 21 (18) ◽

pp. 6198-6209 ◽

Cited By ~ 92

Author(s):

Jijun Cheng ◽

Tae-Sik Park ◽

Anthony S. Fischl ◽

Xiang S. Ye

Keyword(s):

Cell Cycle ◽

Actin Cytoskeleton ◽

Aspergillus Nidulans ◽

Cell Polarity ◽

Cell Cycle Progression ◽

Polarized Growth ◽

Serine Palmitoyltransferase ◽

Cycle Progression ◽

Marked Accumulation ◽

Sphingolipid Biosynthesis

ABSTRACT Sphingolipids are major components of the plasma membrane of eukaryotic cells and were once thought of merely as structural components of the membrane. We have investigated effects of inhibiting sphingolipid biosynthesis, both in germinating spores and growing hyphae of Aspergillus nidulans. In germinating spores, genetic or pharmacological inactivation of inositol phosphorylceramide (IPC) synthase arrests the cell cycle in G1 and also prevents polarized growth during spore germination. However, inactivation of IPC synthase not only eliminates sphingolipid biosynthesis but also leads to a marked accumulation of ceramide, its upstream intermediate. We therefore inactivated serine palmitoyltransferase, the first enzyme in the sphingolipid biosynthesis pathway, to determine effects of inhibiting sphingolipid biosynthesis without an accumulation of ceramide. This inactivation also prevented polarized growth but did not affect nuclear division of germinating spores. To see if sphingolipid biosynthesis is required to maintain polarized growth, and not just to establish polarity, we inhibited sphingolipid biosynthesis in cells in which polarity was already established. This inhibition rapidly abolished normal cell polarity and promoted cell tip branching, which normally never occurs. Cell tip branching was closely associated with dramatic changes in the normally highly polarized actin cytoskeleton and found to be dependent on actin function. The results indicate that sphingolipids are essential for the establishment and maintenance of cell polarity via control of the actin cytoskeleton and that accumulation of ceramide is likely responsible for arresting the cell cycle in G1.

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