Browse
Submit Data
Databases
API
Help

Dataset Information

13 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

SSSPTA is essential for serine palmitoyltransferase function during development and hematopoiesis.

ABSTRACT: Serine palmitoyltransferase complex (SPT) mediates the first and rate-limiting step in the de novo sphingolipid biosynthetic pathway. The larger subunits SPTLC1 and SPTLC2/SPTLC3 together form the catalytic core while a smaller third subunit either SSSPTA or SSSPTB has been shown to increase the catalytic efficiency and provide substrate specificity for the fatty acyl-CoA substrates. The in vivo biological significance of these smaller subunits in mammals is still unknown. Here, using two null mutants, a conditional null for ssSPTa and a null mutant for ssSPTb, we show that SSSPTA is essential for embryogenesis and mediates much of the known functions of the SPT complex in mammalian hematopoiesis. The ssSPTa null mutants are embryonic lethal at E6.5 much like the Sptlc1 and Sptlc2 null alleles. Mx1-Cre induced deletion of ssSPTa leads to lethality and myelopoietic defect. Chimeric and competitive bone marrow transplantation experiments show that the defect in myelopoiesis is accompanied by an expansion of the Lin^-Sca1⁺c-Kit⁺ stem and progenitor compartment. Progenitor cells that fail to differentiate along the myeloid lineage display evidence of endoplasmic reticulum stress. On the other hand, ssSPTb null mice are homozygous viable, and analyses of the bone marrow cells show no significant difference in the proliferation and differentiation of the adult hematopoietic compartment. SPTLC1 is an obligatory subunit for the SPT function, and because Sptlc1^-/- and ssSPTa^-/- mice display similar defects during development and hematopoiesis, we conclude that an SPT complex that includes SSSPTA mediates much of its developmental and hematopoietic functions in a mammalian model.

SUBMITTER: Parthibane V

PROVIDER: S-EPMC8047174 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

Essential role for mitochondrial thioredoxin reductase in hematopoiesis, heart development, and heart function.

Project description:Oxygen radicals regulate many physiological processes, such as signaling, proliferation, and apoptosis, and thus play a pivotal role in pathophysiology and disease development. There are at least two thioredoxin reductase/thioredoxin/peroxiredoxin systems participating in the cellular defense against oxygen radicals. At present, relatively little is known about the contribution of individual enzymes to the redox metabolism in different cell types. To begin to address this question, we generated and characterized mice lacking functional mitochondrial thioredoxin reductase (TrxR2). Ubiquitous Cre-mediated inactivation of TrxR2 is associated with embryonic death at embryonic day 13. TrxR2(TrxR2(-/-)minus;/TrxR2(-/-)minus;) embryos are smaller and severely anemic and show increased apoptosis in the liver. The size of hematopoietic colonies cultured ex vivo is dramatically reduced. TrxR2-deficient embryonic fibroblasts are highly sensitive to endogenous oxygen radicals when glutathione synthesis is inhibited. Besides the defect in hematopoiesis, the ventricular heart wall of TrxR2(TrxR2(-/-)minus;/TrxR2(-/-)minus;) embryos is thinned and proliferation of cardiomyocytes is decreased. Cardiac tissue-restricted ablation of TrxR2 results in fatal dilated cardiomyopathy, a condition reminiscent of that in Keshan disease and Friedreich's ataxia. We conclude that TrxR2 plays a pivotal role in both hematopoiesis and heart function.

| S-EPMC522221 | biostudies-other

Serine Palmitoyltransferase Controls Stemness of Intestinal Progenitors.

Project description:This SuperSeries is composed of the SubSeries listed below.

2022-11-01 | GSE188676 | GEO

Dynamics of sphingolipids and the serine palmitoyltransferase complex in rat oligodendrocytes during myelination.

Project description:Myelin is a unique lipid-rich membrane structure that accelerates neurotransmission and supports neuronal function. Sphingolipids are critical myelin components. Yet sphingolipid content and synthesis have not been well characterized in oligodendrocytes, the myelin-producing cells of the CNS. Here, using quantitative real-time PCR, LC-MS/MS-based lipid analysis, and biochemical assays, we examined sphingolipid synthesis during the peak period of myelination in the postnatal rat brain. Importantly, we characterized sphingolipid production in isolated oligodendrocytes. We analyzed sphingolipid distribution and levels of critical enzymes and regulators in the sphingolipid biosynthetic pathway, with focus on the serine palmitoyltransferase (SPT) complex, the rate-limiting step in this pathway. During myelination, levels of the major SPT subunits increased and oligodendrocyte maturation was accompanied by extensive alterations in the composition of the SPT complex. These included changes in the relative levels of two alternative catalytic subunits, SPTLC2 and -3, in the relative levels of isoforms of the small subunits, ssSPTa and -b, and in the isoform distribution of the SPT regulators, the ORMDLs. Myelination progression was accompanied by distinct changes in both the nature of the sphingoid backbone and the N-acyl chains incorporated into sphingolipids. We conclude that the distribution of these changes among sphingolipid family members is indicative of a selective channeling of the ceramide backbone toward specific downstream metabolic pathways during myelination. Our findings provide insights into myelin production in oligodendrocytes and suggest how dysregulation of the biosynthesis of this highly specialized membrane could contribute to demyelinating diseases.

| S-EPMC7112141 | biostudies-literature

Serine palmitoyltransferase assembles at ER-mitochondria contact sites.

Project description:The accumulation of sphingolipid species in the cell contributes to the development of obesity and neurological disease. However, the subcellular localization of sphingolipid-synthesizing enzymes is unclear, limiting the understanding of where and how these lipids accumulate inside the cell and why they are toxic. Here, we show that SPTLC2, a subunit of the serine palmitoyltransferase (SPT) complex, catalyzing the first step in de novo sphingolipid synthesis, localizes dually to the ER and the outer mitochondrial membrane. We demonstrate that mitochondrial SPTLC2 interacts and forms a complex in trans with the ER-localized SPT subunit SPTLC1. Loss of SPTLC2 prevents the synthesis of mitochondrial sphingolipids and protects from palmitate-induced mitochondrial toxicity, a process dependent on mitochondrial ceramides. Our results reveal the in trans assembly of an enzymatic complex at an organellar membrane contact site, providing novel insight into the localization of sphingolipid synthesis and the composition and function of ER-mitochondria contact sites.

| S-EPMC8605320 | biostudies-literature

Murine endothelial serine palmitoyltransferase 1 (SPTLC1) is required for vascular development and systemic sphingolipid homeostasis.

Project description:Serine palmitoyl transferase (SPT), the rate-limiting enzyme in the de novo synthesis of sphingolipids (SL), is needed for embryonic development, physiological homeostasis, and response to stress. The functions of de novo SL synthesis in vascular endothelial cells (EC), which line the entire circulatory system, are not well understood. Here, we show that the de novo SL synthesis in EC not only regulates vascular development but also maintains circulatory and peripheral organ SL levels. Mice with an endothelial-specific gene knockout of SPTLC1 (Sptlc1 ECKO), an essential subunit of the SPT complex, exhibited reduced EC proliferation and tip/stalk cell differentiation, resulting in delayed retinal vascular development. In addition, Sptlc1 ECKO mice had reduced retinal neovascularization in the oxygen-induced retinopathy model. Mechanistic studies suggest that EC SL produced from the de novo pathway are needed for lipid raft formation and efficient VEGF signaling. Post-natal deletion of the EC Sptlc1 also showed rapid reduction of several SL metabolites in plasma, red blood cells, and peripheral organs (lung and liver) but not in the retina, part of the central nervous system (CNS). In the liver, EC de novo SL synthesis was important for acetaminophen-induced rapid ceramide elevation and hepatotoxicity. These results suggest that EC-derived SL metabolites are in constant flux between the vasculature, circulatory elements, and parenchymal cells of non-CNS organs. Taken together, our data point to the central role of the endothelial SL biosynthesis in maintaining vascular development, neovascular proliferation, non-CNS tissue metabolic homeostasis, and hepatocyte response to stress.

| S-EPMC9578713 | biostudies-literature

Serine Palmitoyltransferase Controls Stemness of Intestinal Progenitors [bulk RNA-Seq]

Project description:Cancers of the gastrointestinal tract including esophageal adenocarcinomas, colorectal cancers, and cancers of the gastric cardia are common comorbidities of obesity. Excessive delivery of macronutrients to the cells lining the gut can increase one’s risk for these cancer by inducing imbalances in the rate of intestinal stem cell proliferation vs. differentiation, which can produce polyps and other aberrant growths. We demonstrate that serine palmitoyltransferase (SPT), which diverts dietary fatty and amino acids into the sphingolipid biosynthesis pathway, is a critical modulator of intestinal stem cell homeostasis. SPT and other enzymes in the biosynthetic pathway are upregulated in human colon tumors. These enzymes produce sphingolipids that serve as pro-stemness signals that stimulate peroxisome-proliferator activated receptor alpha (PPARa)-mediated induction of fatty acid binding protein-1. This increases fatty acid uptake and oxidation and enhances the stemness program. Serine palmitoyltransferase thus serves as a critical link between dietary macronutrients, epithelial regeneration, and cancer risk.

2022-11-01 | GSE188674 | GEO

Characterization of mutant serine palmitoyltransferase 1 in LY-B cells.

Project description:CHO-LY-B cells have been useful in studies of sphingolipid metabolism and function because they lack serine palmitoyltransferase (SPT) activity. Cloning and sequencing of the SPT1 transcript of LY-B cells identified the mutation as a guanine to adenine change at nucleotide 738, causing a G246R transformation. Western blots revealed low expression of the mutant SPT1 peptide, but activity was not detectable by mass spectrometric analysis of [(13)C]-palmitate incorporation into sphinganine, sphingosine, 1-deoxysphinganine, or 1-desoxymethylsphinganine. Treatment of LY-B cells with chemical chaperones (DMSO or glycerol) increased the amounts of mutant SPT1 as well as SPT2, but SPT activity was not restored. This study has established that G246R mutation in hamster SPT1 results in the loss of SPT activity.

| S-EPMC4638125 | biostudies-literature

Multifunctional role of His159in the catalytic reaction of serine palmitoyltransferase.

Project description:Serine palmitoyltransferase (SPT) belongs to the fold type I family of the pyridoxal 5'-phosphate (PLP)-dependent enzyme and forms 3-ketodihydrosphingosine (KDS) from l-serine and palmitoyl-CoA. Like other alpha-oxamine synthase subfamily enzymes, SPT is different from most of the fold type I enzymes in that its re face of the PLP-Lys aldimine is occupied by a His residue (His(159)) instead of an aromatic amino acid residue. His(159) was changed into alanine or aromatic amino acid residues to examine its role during catalysis. All mutant SPTs formed the PLP-l-serine aldimine with dissociation constants several 10-fold higher than that of the wild type SPT and catalyzed the abortive transamination of l-serine. These results indicate that His(159) is not only the anchoring site for l-serine but regulates the alpha-deprotonation of l-serine by fixing the conformation of the PLP-l-serine aldimine to prevent unwanted side reactions. Only H159A SPT retained activity and showed a prominent 505-nm absorption band of the quinonoid species during catalysis. Global analysis of the time-resolved spectra suggested the presence of the two quinonoid intermediates, the first formed from the PLP-l-serine aldimine and the second from the PLP-KDS aldimine. Accumulation of these quinonoid intermediates indicated that His(159) promotes both the Claisen-type condensation as an acid catalyst and the protonation at Calpha of the second quinonoid to form the PLP-KDS aldimine. These results, combined with the previous model building study (Ikushiro, H., Fujii, S., Shiraiwa, Y., and Hayashi, H. (2008) J. Biol. Chem. 283, 7542-7553), lead us to propose a novel mechanism, in which His(159) plays multiple roles by exploiting the stereochemistry of Dunathan's conjecture.

| S-EPMC2786316 | biostudies-literature

Essential Function of the Serine Hydroxymethyl Transferase (SHMT) Gene During Rapid Syncytial Cell Cycles in Drosophila.

Project description:Many metabolic enzymes are evolutionarily highly conserved and serve a central function in the catabolism and anabolism of cells. The serine hydroxymethyl transferase (SHMT) catalyzing the conversion of serine and glycine and vice versa feeds into tetrahydrofolate (THF)-mediated C1 metabolism. We identified a Drosophila mutation in SHMT (CG3011) in a screen for blastoderm mutants. Embryos from SHMT mutant germline clones specifically arrest the cell cycle in interphase 13 at the time of the midblastula transition (MBT) and prior to cellularization. The phenotype is due to a loss of enzymatic activity as it cannot be rescued by an allele with a point mutation in the catalytic center but by an allele based on the SHMT coding sequence from Escherichia coli The onset of zygotic gene expression and degradation of maternal RNAs in SHMT mutant embryos are largely similar to that in wild-type embryos. The specific timing of the defects in SHMT mutants indicates that at least one of the SHMT-dependent metabolites becomes limiting in interphase 13, if it is not produced by the embryo. Our data suggest that mutant eggs contain maternally-provided and SHMT-dependent metabolites in amounts that suffice for early development until interphase 13.

| S-EPMC5499137 | biostudies-literature

Serine Palmitoyltransferase Controls Stemness of Intestinal Progenitors [single cell RNA-Seq]

2022-11-01 | GSE188675 | GEO