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Thorsten Hornemann - One of the best experts on this subject based on the ideXlab platform.
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subunit composition of the mammalian serine palmitoyltransferase defines the spectrum of straight and methyl branched long chain bases
Proceedings of the National Academy of Sciences of the United States of America, 2020Co-Authors: Museer A Lone, Arnold Von Eckardstein, Andreas J Hulsmeier, Essa M Saied, Gergely Karsai, Christoph Arenz, Thorsten HornemannAbstract:Sphingolipids (SLs) are chemically diverse lipids that have important structural and signaling functions within mammalian cells. SLs are commonly defined by the presence of a long-chain base (LCB) that is normally formed by the conjugation of l-serine and palmitoyl-CoA. This pyridoxal 5-phosphate (PLP)-dependent reaction is mediated by the enzyme serine-palmitoyltransferase (SPT). However, SPT can also metabolize other acyl-CoAs, in the range of C14 to C18, forming a variety of LCBs that differ by structure and function. Mammalian SPT consists of three core subunits: SPTLC1, SPTLC2, and SPTLC3. Whereas SPTLC1 and SPTLC2 are ubiquitously expressed, SPTLC3 expression is restricted to certain tissues only. The influence of the individual subunits on enzyme activity is not clear. Using cell models deficient in SPTLC1, SPTLC2, and SPTLC3, we investigated the role of each subunit on enzyme activity and the LCB product spectrum. We showed that SPTLC1 is essential for activity, whereas SPTLC2 and SPTLC3 are partly redundant but differ in their enzymatic properties. SPTLC1 in combination with SPTLC2 specifically formed C18, C19, and C20 LCBs while the combination of SPTLC1 and SPTLC3 yielded a broader product spectrum. We identified anteiso-branched-C18 SO (meC18SO) as the primary product of the SPTLC3 reaction. The meC18SO was synthesized from anteiso-methyl-palmitate, in turn synthesized from a precursor metabolite generated in the isoleucine catabolic pathway. The meC18SO is metabolized to ceramides and complex SLs and is a constituent of human low- and high-density lipoproteins.
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HSAN1 mutations in serine palmitoyltransferase reveal a close structure-function-phenotype relationship
Human Molecular Genetics, 2015Co-Authors: Heiko Bode, Irina Alecu, Arnold Von Eckardstein, Yu Wei, Florence Bourquin, Saranya Suriyanarayanan, Alaa Othman, Thorsten HornemannAbstract:Hereditary sensory and autonomic neuropathy type 1 (HSAN1) is a rare autosomal dominant inherited peripheral neuropathy caused by mutations in the SPTLC1 and SPTLC2 subunits of serine palmitoyltransferase (SPT). The mutations induce a permanent shift in the substrate preference from L-serine to L-alanine, which results in the pathological formation of atypical and neurotoxic 1-deoxy-sphingolipids (1-deoxySL). Here we compared the enzymatic properties of 11 SPTLC1 and six SPTLC2 mutants using a uniform isotope labelling approach. In total, eight SPT mutants (STPLC1p.C133W, p.C133Y, p.S331F, p.S331Y and SPTLC2p.A182P, p.G382V, p.S384F, p.I504F) were associated with increased 1-deoxySL synthesis. Despite earlier reports, canonical activity with l-serine was not reduced in any of the investigated SPT mutants. Three variants (SPTLC1p.S331F/Y and SPTLC2p.I505Y) showed an increased canonical activity and increased formation of C20 sphingoid bases. These three mutations are associated with an exceptionally severe HSAN1 phenotype, and increased C20 sphingosine levels were also confirmed in plasma of patients. A principal component analysis of the analysed sphingoid bases clustered the mutations into three separate entities. Each cluster was related to a distinct clinical outcome (no, mild and severe HSAN1 phenotype). A homology model based on the protein structure of the prokaryotic SPT recapitulated the same grouping on a structural level. Mutations associated with the mild form clustered around the active site, whereas mutations associated with the severe form were located on the surface of the protein. In conclusion, we showed that HSAN1 mutations in SPT have distinct biochemical properties, which allowed for the prediction of the clinical symptoms on the basis of the plasma sphingoid base profile.
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Sinéad M. Murphy, MD, MRCPI*
2015Co-Authors: Daniela Ernst Msc, Thorsten Hornemann, James M Polke, Henry Houlden, Yu Wei Msc, Matilde Laurà, Yo-tsen Liu, Julian Blake Mrcp, Mary M. ReillyAbstract:Supplemental data at www.neurology.org Hereditary sensory and autonomic neuropathy type 1 (HSANI) caused by a novel mutation in SPTLC2 Objective: To describe the clinical and neurophysiologic phenotype of a family with hereditary sensory and autonomic neuropathy type 1 (HSANI) due to a novel mutation in SPTLC2 and to characterize the biochemical properties of this mutation. Methods: We screened 107 patients with HSAN who were negative for other genetic causes for mutations in SPTLC2. The biochemical properties of a new mutation were characterized in cell-free and cell-based activity assays. Results: A novel mutation (A182P) was found in 2 subjects of a single family. The phenotype of the 2 subjects was an ulcero-mutilating sensory-predominant neuropathy as described previously for patients with HSANI, but with prominent motor involvement and earlier disease onset in the firs
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THE SPTLC3 SUBUNIT OF SERINE- PALMITOYLTRANSFERASE GENERATES SHORT CHAIN SPHINGOID BASES
2015Co-Authors: Thorsten Hornemann, Anke Penno, Markus F Rutti, Daniela Ernst, Fatma Kivrak-pfiffnerAbstract:The enzyme serine-palmitoyltransferase (SPT) catalyses the rate limiting step in the de-novo synthesis of sphingolipids. Previously the mammalian SPT was described as a heterodimer composed of two subunits- SPTLC1 and SPTLC2. Recently we identified a novel third SPT subunit (SPTLC3). SPTLC3 shows about 68 % identity to SPTLC2 and also includes a PLP consensus motif. Here we report that the overexpression of SPTLC3 in HEK293 cells leads to the formation of two new sphingoid base metabolites, namely C16-sphinganine and C16-sphingosine. SPTLC
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Hereditary sensory and autonomic neuropathy type 1 (HSANI) caused by a novel mutation in SPTLC2
Neurology, 2013Co-Authors: Sinead M Murphy, Daniela Ernst, Yu Wei, James M Polke, Henry Houlden, Matilde Laurà, Yo-tsen Liu, Julian Blake, John B Winer, Thorsten HornemannAbstract:Objective: To describe the clinical and neurophysiologic phenotype of a family with hereditary sensory and autonomic neuropathy type 1 (HSANI) due to a novel mutation in SPTLC2 and to characterize the biochemical properties of this mutation. Methods: We screened 107 patients with HSAN who were negative for other genetic causes for mutations in SPTLC2. The biochemical properties of a new mutation were characterized in cell-free and cell-based activity assays. Results: A novel mutation (A182P) was found in 2 subjects of a single family. The phenotype of the 2 subjects was an ulcero-mutilating sensory-predominant neuropathy as described previously for patients with HSANI, but with prominent motor involvement and earlier disease onset in the first decade of life. Affected patients had elevated levels of plasma 1-deoxysphingolipids (1-deoxySLs). Biochemically, the A182P mutation was associated with a reduced canonical activity but an increased alternative activity with alanine, which results in largely increased 1-deoxySL levels, supporting their pathogenicity. Conclusion: This study confirms that mutations in SPTLC2 are associated with increased deoxySL formation causing HSANI. Neurology� 2013;80:1–6
Yu Wei - One of the best experts on this subject based on the ideXlab platform.
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ORIGINAL PAPER Novel HSAN1 Mutation in Serine Palmitoyltransferase Resides at a Putative Phosphorylation Site That Is Involved in Regulating Substrate Specificity
2016Co-Authors: Daniela Ernst, Anke Penno, Yu Wei, Alaa Othman, Matilde Laurà, Yo-tsen Liu, Julian Blake, Karthik Sathiyanadan, Sinéad M. Murphy, Michael DonaghyAbstract:Abstract 1-Deoxysphingolipids (1-deoxySL) are atypical sphingolipids that are formed by the enzyme serine pal-mitoyltransferase (SPT) due to a promiscuous use of L-alanine over its canonical substrate L-serine. Several mutations in SPT are associated with the hereditary sensory and autonomic neuropathy type I (HSAN1). The current hypothesis is that these mutations induce a permanent shift in the affinity from L-serine toward L-alanine which results in a pathologically increased 1-deoxySL formation in HSAN1 patients. Also, wild-type SPT forms 1-deoxySL under certain conditions, and elevated levels were found in individuals with the metabolic syndrome and diabetes. However, the molecular mechanisms which control the substrate shift of the wild-type enzyme are not understood. Here, we report a novel SPTLC2–S384F variant in tw
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The Variant p.(Arg183Trp) in SPTLC2 Causes Late-Onset Hereditary Sensory Neuropathy
NeuroMolecular Medicine, 2016Co-Authors: Saranya Suriyanarayanan, Yu Wei, Beate Schlotter-weigel, Mari Auranen, Jussi Toppila, Anders Paetau, Maria Shcherbii, Eino Palin, Tarja Lohioja, Ulrike SchönAbstract:Hereditary sensory and autonomic neuropathy 1 (HSAN1) is an autosomal dominant disorder that can be caused by variants in SPTLC1 or SPTLC2, encoding subunits of serine palmitoyl-CoA transferase. Disease variants alter the enzyme’s substrate specificity and lead to accumulation of neurotoxic 1-deoxysphingolipids. We describe two families with autosomal dominant HSAN1C caused by a new variant in SPTLC2 , c.547C>T, p.(Arg183Trp). The variant changed a conserved amino acid and was not found in public variant databases. All patients had a relatively mild progressive distal sensory impairment, with onset after age 50. Small fibers were affected early, leading to abnormalities on quantitative sensory testing. Sural biopsy revealed a severe chronic axonal neuropathy with subtotal loss of myelinated axons, relatively preserved number of non-myelinated fibers and no signs for regeneration. Skin biopsy with PGP9.5 labeling showed lack of intraepidermal nerve endings early in the disease. Motor manifestations developed later in the disease course, but there was no evidence of autonomic involvement. Patients had elevated serum 1-deoxysphingolipids, and the variant protein produced elevated amounts of 1-deoxysphingolipids in vitro, which proved the pathogenicity of the variant. Our results expand the genetic spectrum of HSAN1C and provide further detail about the clinical characteristics. Sequencing of SPTLC2 should be considered in all patients presenting with mild late-onset sensory-predominant small or large fiber neuropathy.
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The Variant p.(Arg183Trp) in SPTLC2 Causes Late-Onset Hereditary Sensory Neuropathy
'Springer Science and Business Media LLC', 2016Co-Authors: Suriyanarayanan Saranya, Yu Wei, Auranen Mari, Toppila Jussi, Paetau Anders, Shcherbii Maria, Palin Eino, Lohioja Tarja, Schlotter-weigel Beate, Schoen UlrikeAbstract:Hereditary sensory and autonomic neuropathy 1 (HSAN1) is an autosomal dominant disorder that can be caused by variants in SPTLC1 or SPTLC2, encoding subunits of serine palmitoyl-CoA transferase. Disease variants alter the enzyme's substrate specificity and lead to accumulation of neurotoxic 1-deoxysphingolipids. We describe two families with autosomal dominant HSAN1C caused by a new variant in SPTLC2, c.547C > T, p.(Arg183Trp). The variant changed a conserved amino acid and was not found in public variant databases. All patients had a relatively mild progressive distal sensory impairment, with onset after age 50. Small fibers were affected early, leading to abnormalities on quantitative sensory testing. Sural biopsy revealed a severe chronic axonal neuropathy with subtotal loss of myelinated axons, relatively preserved number of non-myelinated fibers and no signs for regeneration. Skin biopsy with PGP9.5 labeling showed lack of intraepidermal nerve endings early in the disease. Motor manifestations developed later in the disease course, but there was no evidence of autonomic involvement. Patients had elevated serum 1-deoxysphingolipids, and the variant protein produced elevated amounts of 1-deoxysphingolipids in vitro, which proved the pathogenicity of the variant. Our results expand the genetic spectrum of HSAN1C and provide further detail about the clinical characteristics. Sequencing of SPTLC2 should be considered in all patients presenting with mild late-onset sensory-predominant small or large fiber neuropathy.Peer reviewe
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HSAN1 mutations in serine palmitoyltransferase reveal a close structure-function-phenotype relationship
Human Molecular Genetics, 2015Co-Authors: Heiko Bode, Irina Alecu, Arnold Von Eckardstein, Yu Wei, Florence Bourquin, Saranya Suriyanarayanan, Alaa Othman, Thorsten HornemannAbstract:Hereditary sensory and autonomic neuropathy type 1 (HSAN1) is a rare autosomal dominant inherited peripheral neuropathy caused by mutations in the SPTLC1 and SPTLC2 subunits of serine palmitoyltransferase (SPT). The mutations induce a permanent shift in the substrate preference from L-serine to L-alanine, which results in the pathological formation of atypical and neurotoxic 1-deoxy-sphingolipids (1-deoxySL). Here we compared the enzymatic properties of 11 SPTLC1 and six SPTLC2 mutants using a uniform isotope labelling approach. In total, eight SPT mutants (STPLC1p.C133W, p.C133Y, p.S331F, p.S331Y and SPTLC2p.A182P, p.G382V, p.S384F, p.I504F) were associated with increased 1-deoxySL synthesis. Despite earlier reports, canonical activity with l-serine was not reduced in any of the investigated SPT mutants. Three variants (SPTLC1p.S331F/Y and SPTLC2p.I505Y) showed an increased canonical activity and increased formation of C20 sphingoid bases. These three mutations are associated with an exceptionally severe HSAN1 phenotype, and increased C20 sphingosine levels were also confirmed in plasma of patients. A principal component analysis of the analysed sphingoid bases clustered the mutations into three separate entities. Each cluster was related to a distinct clinical outcome (no, mild and severe HSAN1 phenotype). A homology model based on the protein structure of the prokaryotic SPT recapitulated the same grouping on a structural level. Mutations associated with the mild form clustered around the active site, whereas mutations associated with the severe form were located on the surface of the protein. In conclusion, we showed that HSAN1 mutations in SPT have distinct biochemical properties, which allowed for the prediction of the clinical symptoms on the basis of the plasma sphingoid base profile.
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novel hsan1 mutation in serine palmitoyltransferase resides at a putative phosphorylation site that is involved in regulating substrate specificity
Neuromolecular Medicine, 2015Co-Authors: Daniela Ernst, Yu Wei, Alaa Othman, Sinead M Murphy, M Laura, Yo-tsen Liu, Karthik SathiyanadanAbstract:1-Deoxysphingolipids (1-deoxySL) are atypical sphingolipids that are formed by the enzyme serine palmitoyltransferase (SPT) due to a promiscuous use of l-alanine over its canonical substrate l-serine. Several mutations in SPT are associated with the hereditary sensory and autonomic neuropathy type I (HSAN1). The current hypothesis is that these mutations induce a permanent shift in the affinity from l-serine toward l-alanine which results in a pathologically increased 1-deoxySL formation in HSAN1 patients. Also, wild-type SPT forms 1-deoxySL under certain conditions, and elevated levels were found in individuals with the metabolic syndrome and diabetes. However, the molecular mechanisms which control the substrate shift of the wild-type enzyme are not understood. Here, we report a novel SPTLC2–S384F variant in two unrelated HSAN1 families. Affected patients showed elevated plasma 1-deoxySL levels and expression of the S384F mutant in HEK293 cells increased 1-deoxySL formation. Previously, S384 has been reported as one of the two (S384 and Y387) putative phosphorylation sites in SPTLC2. The phosphorylation of wild-type SPTLC2 was confirmed by isoelectric focusing. The impact of an S384 phosphorylation on SPT activity was tested by creating mutants mimicking either a constitutively phosphorylated (S384D, S384E) or non-phosphorylated (S384A, Y387F, Y387F+S384A) protein. The S384D but not the S384E variant was associated with increased 1-deoxySL formation. The other mutations had no influence on activity and substrate affinity. In summary, our data show that S384F is a novel mutation in HSAN1 and that the substrate specificity of wild-type SPT might by dynamically regulated by a phosphorylation at this position.
Michaela Auer-grumbach - One of the best experts on this subject based on the ideXlab platform.
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Loss of Neurological Disease HSAN-I-Associated Gene SPTLC2 Impairs CD8+ T Cell Responses to Infection by Inhibiting T Cell Metabolic Fitness.
Immunity, 2019Co-Authors: Roger Sandhoff, Michaela Auer-grumbach, Vincent Timmerman, Beate Schlotter-weigel, Yanan Ming, Agnes Hotz-wagenblatt, Nathalie Bonello-palot, Pavel SeemanAbstract:Summary Patients with the neurological disorder HSAN-I suffer frequent infections, attributed to a lack of pain sensation and failure to seek care for minor injuries. Whether protective CD8+ T cells are affected in HSAN-I patients remains unknown. Here, we report that HSAN-I-associated mutations in serine palmitoyltransferase subunit SPTLC2 dampened human T cell responses. Antigen stimulation and inflammation induced SPTLC2 expression, and murine T-cell-specific ablation of SPTLC2 impaired antiviral-T-cell expansion and effector function. SPTLC2 deficiency reduced sphingolipid biosynthetic flux and led to prolonged activation of the mechanistic target of rapamycin complex 1 (mTORC1), endoplasmic reticulum (ER) stress, and CD8+ T cell death. Protective CD8+ T cell responses in HSAN-I patient PBMCs and SPTLC2-deficient mice were restored by supplementing with sphingolipids and pharmacologically inhibiting ER stress-induced cell death. Therefore, SPTLC2 underpins protective immunity by translating extracellular stimuli into intracellular anabolic signals and antagonizes ER stress to promote T cell metabolic fitness.
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Loss of Neurological Disease HSAN-I-Associated Gene SPTLC2 Impairs CD8(+) T Cell Responses to Infection by Inhibiting T Cell Metabolic Fitness
IMMUNITY, 2019Co-Authors: Roger Sandhoff, Michaela Auer-grumbach, Vincent Timmerman, Beate Schlotter-weigel, Yanan Ming, Agnes Hotz-wagenblatt, Nathalie Bonello-palot, Pavel Seeman, Wolfgang N. Loescher, Markus ReindlAbstract:Patients with the neurological disorder HSAN-I suffer frequent infections, attributed to a lack of pain sensation and failure to seek care for minor injuries. Whether protective CD8(+) T cells are affected in HSAN-I patients remains unknown. Here, we report that HSAN-I-associated mutations in serine palmitoyltransferase subunit SPTLC2 dampened human T cell responses. Antigen stimulation and inflammation induced SPTLC2 expression, and murine T-cell-specific ablation of SPTLC2 impaired antiviralT-cell expansion and effector function. SPTLC2 deficiency reduced sphingolipid biosynthetic flux and led to prolonged activation of the mechanistic target of rapamycin complex 1 (mTORC1), endoplasmic reticulum (ER) stress, and CD8(+) T cell death. Protective CD8(+) T cell responses in HSAN-I patient PBMCs and SPTLC2-deficient mice were restored by supplementing with sphingolipids and pharmacologically inhibiting ER stress-induced cell death. Therefore, SPTLC2 underpins protective immunity by translating extracellular stimuli into intracellular anabolic signals and antagonizes ER stress to promote T cell metabolic fitness.
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ARTICLE Mutations in the SPTLC2 Subunit of Serine Palmitoyltransferase Cause Hereditary Sensory and Autonomic Neuropathy Type I
2015Co-Authors: Annelies Rotthier, Anke Penno, Michaela Auer-grumbach, Kim Van Hoof, Katrien Janssens, Jonathan Baets, An Jacobs, Els De Vriendt, Leonardo Almeida-souza, Beate Schlotter-weigelAbstract:Hereditary sensory and autonomic neuropathy type I (HSAN-I) is an axonal peripheral neuropathy associated with progressive distal f g ath ie u a ga cts sti tions in the first subunit (SPTLC1 [MIM 605712]) of the methyl-SA) instead of sphinganine (SA). These alterna-The Ameenzyme serine palmitoyltransferase (SPT).4–6 The SPT enzyme is a multisubunit structure, consisting of dimeric subunits of SPTLC1 with either SPTLC2 (MIM 605713) or SPTLC3 (MIM 611120).7 It is associated with the endo-plasmic reticulum (ER), where it catalyzes the pyridoxal
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Mutations at Ser331 in the HSN type I gene SPTLC1 are associated with a distinct syndromic phenotype.
European journal of medical genetics, 2013Co-Authors: Michaela Auer-grumbach, Heiko Bode, Thomas R. Pieber, Maria Schabhüttl, Dirk Fischer, Rainer Seidl, Elisabeth Graf, Thomas Wieland, Reinhard Schuh, Gerda VacariuAbstract:Mutations in the serine palmitoyltransferase subunit 1 (SPTLC1) gene are the most common cause of hereditary sensory neuropathy type 1 (HSN1). Here we report the clinical and molecular consequences of a particular mutation (p.S331Y) in SPTLC1 affecting a patient with severe, diffuse muscle wasting and hypotonia, prominent distal sensory disturbances, joint hypermobility, bilateral cataracts and considerable growth retardation. Normal plasma sphingolipids were unchanged but 1-deoxy-sphingolipids were significantly elevated. In contrast to other HSN patients reported so far, our findings strongly indicate that mutations at amino acid position Ser331 of the SPTLC1 gene lead to a distinct syndrome.
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Characterization of two mutations in the SPTLC1 subunit of serine palmitoyltransferase associated with hereditary sensory and autonomic neuropathy type I.
Human Mutation, 2011Co-Authors: Annelies Rotthier, Anke Penno, Michaela Auer-grumbach, Bernd Rautenstrauss, Georg M. Stettner, Bob Asselbergh, Kim Van Hoof, Heinrich Sticht, Nicholas Levy, Vincent TimmermanAbstract:Hereditary sensory and autonomic neuropathy type I (HSAN-I) is an axonal peripheral neuropathy leading to progressive distal sensory loss and severe ulcerations. Mutations in SPTLC1 and SPTLC2, encoding the two subunits of serine palmitoyltransferase (SPT), the enzyme catalyzing the first and rate-limiting step in the de novo synthesis of sphingolipids, have been reported to cause HSAN-I. Here, we demonstrate that the SPTLC1 mutations p.S331F and p.A352V result in a reduction of SPT activity in vitro and are associated with increased levels of the deoxysphingoid bases 1-deoxy-sphinganine and 1-deoxymethyl-sphinganine in patients' plasma samples. Stably expressing p.S331F-SPTLC1 HEK293T cell lines likewise show accumulation of deoxysphingoid bases, but this accumulation is not observed in HEK293T cells overexpressing p.A352V-SPTLC1. These results confirm that the increased formation of deoxysphingoid bases is a key feature for HSAN-I as it is associated with all pathogenic SPTLC1 and SPTLC2 mutations reported so far, but also warrant for caution in the interpretation of in vitro data.
Anke Penno - One of the best experts on this subject based on the ideXlab platform.
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ORIGINAL PAPER Novel HSAN1 Mutation in Serine Palmitoyltransferase Resides at a Putative Phosphorylation Site That Is Involved in Regulating Substrate Specificity
2016Co-Authors: Daniela Ernst, Anke Penno, Yu Wei, Alaa Othman, Matilde Laurà, Yo-tsen Liu, Julian Blake, Karthik Sathiyanadan, Sinéad M. Murphy, Michael DonaghyAbstract:Abstract 1-Deoxysphingolipids (1-deoxySL) are atypical sphingolipids that are formed by the enzyme serine pal-mitoyltransferase (SPT) due to a promiscuous use of L-alanine over its canonical substrate L-serine. Several mutations in SPT are associated with the hereditary sensory and autonomic neuropathy type I (HSAN1). The current hypothesis is that these mutations induce a permanent shift in the affinity from L-serine toward L-alanine which results in a pathologically increased 1-deoxySL formation in HSAN1 patients. Also, wild-type SPT forms 1-deoxySL under certain conditions, and elevated levels were found in individuals with the metabolic syndrome and diabetes. However, the molecular mechanisms which control the substrate shift of the wild-type enzyme are not understood. Here, we report a novel SPTLC2–S384F variant in tw
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ARTICLE Mutations in the SPTLC2 Subunit of Serine Palmitoyltransferase Cause Hereditary Sensory and Autonomic Neuropathy Type I
2015Co-Authors: Annelies Rotthier, Anke Penno, Michaela Auer-grumbach, Kim Van Hoof, Katrien Janssens, Jonathan Baets, An Jacobs, Els De Vriendt, Leonardo Almeida-souza, Beate Schlotter-weigelAbstract:Hereditary sensory and autonomic neuropathy type I (HSAN-I) is an axonal peripheral neuropathy associated with progressive distal f g ath ie u a ga cts sti tions in the first subunit (SPTLC1 [MIM 605712]) of the methyl-SA) instead of sphinganine (SA). These alterna-The Ameenzyme serine palmitoyltransferase (SPT).4–6 The SPT enzyme is a multisubunit structure, consisting of dimeric subunits of SPTLC1 with either SPTLC2 (MIM 605713) or SPTLC3 (MIM 611120).7 It is associated with the endo-plasmic reticulum (ER), where it catalyzes the pyridoxal
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THE SPTLC3 SUBUNIT OF SERINE- PALMITOYLTRANSFERASE GENERATES SHORT CHAIN SPHINGOID BASES
2015Co-Authors: Thorsten Hornemann, Anke Penno, Markus F Rutti, Daniela Ernst, Fatma Kivrak-pfiffnerAbstract:The enzyme serine-palmitoyltransferase (SPT) catalyses the rate limiting step in the de-novo synthesis of sphingolipids. Previously the mammalian SPT was described as a heterodimer composed of two subunits- SPTLC1 and SPTLC2. Recently we identified a novel third SPT subunit (SPTLC3). SPTLC3 shows about 68 % identity to SPTLC2 and also includes a PLP consensus motif. Here we report that the overexpression of SPTLC3 in HEK293 cells leads to the formation of two new sphingoid base metabolites, namely C16-sphinganine and C16-sphingosine. SPTLC
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oral l serine supplementation reduces production of neurotoxic deoxysphingolipids in mice and humans with hereditary sensory autonomic neuropathy type 1
Journal of Clinical Investigation, 2011Co-Authors: Kevin Garofalo, Thorsten Hornemann, Anke Penno, Arnold Von Eckardstein, Matthew P. Frosch, Robert H. Brown, B P Schmidt, Florian EichlerAbstract:Hereditary sensory and autonomic neuropathy type 1 (HSAN1) causes sensory loss that predominantly affects the lower limbs, often preceded by hyperpathia and spontaneous shooting or lancinating pain. It is caused by several missense mutations in the genes encoding 2 of the 3 subunits of the enzyme serine palmitoyltransferase (SPT). The mutant forms of the enzyme show a shift from their canonical substrate l-serine to the alternative substrate l-alanine. This shift leads to increased formation of neurotoxic deoxysphingolipids (dSLs). Our initial analysis showed that in HEK cells transfected with SPTLC1 mutants, dSL generation was modulated in vitro in the presence of various amino acids. We therefore examined whether in vivo specific amino acid substrate supplementation influenced dSL levels and disease severity in HSAN1. In mice bearing a transgene expressing the C133W SPTLC1 mutant linked to HSAN1, a 10% l-serine–enriched diet reduced dSL levels. l-serine supplementation also improved measures of motor and sensory performance as well as measures of male fertility. In contrast, a 10% l-alanine–enriched diet increased dSL levels and led to severe peripheral neuropathy. In a pilot study with 14 HSAN1 patients, l-serine supplementation similarly reduced dSL levels. These observations support the hypothesis that an altered substrate selectivity of the mutant SPT is key to the pathophysiology of HSAN1 and raise the prospect of l-serine supplementation as a first treatment option for this disorder.
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Characterization of two mutations in the SPTLC1 subunit of serine palmitoyltransferase associated with hereditary sensory and autonomic neuropathy type I.
Human Mutation, 2011Co-Authors: Annelies Rotthier, Anke Penno, Michaela Auer-grumbach, Bernd Rautenstrauss, Georg M. Stettner, Bob Asselbergh, Kim Van Hoof, Heinrich Sticht, Nicholas Levy, Vincent TimmermanAbstract:Hereditary sensory and autonomic neuropathy type I (HSAN-I) is an axonal peripheral neuropathy leading to progressive distal sensory loss and severe ulcerations. Mutations in SPTLC1 and SPTLC2, encoding the two subunits of serine palmitoyltransferase (SPT), the enzyme catalyzing the first and rate-limiting step in the de novo synthesis of sphingolipids, have been reported to cause HSAN-I. Here, we demonstrate that the SPTLC1 mutations p.S331F and p.A352V result in a reduction of SPT activity in vitro and are associated with increased levels of the deoxysphingoid bases 1-deoxy-sphinganine and 1-deoxymethyl-sphinganine in patients' plasma samples. Stably expressing p.S331F-SPTLC1 HEK293T cell lines likewise show accumulation of deoxysphingoid bases, but this accumulation is not observed in HEK293T cells overexpressing p.A352V-SPTLC1. These results confirm that the increased formation of deoxysphingoid bases is a key feature for HSAN-I as it is associated with all pathogenic SPTLC1 and SPTLC2 mutations reported so far, but also warrant for caution in the interpretation of in vitro data.
Robert H. Brown - One of the best experts on this subject based on the ideXlab platform.
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Mutations in the SPTLC1 gene are a cause of amyotrophic lateral sclerosis that may be amenable to serine supplementation [preprint]
2019Co-Authors: Janel O. Johnson, Robert H. Brown, Ruth Chia, John LandersAbstract:Abstract SPTLC1 encodes a critical subunit of serine palmitoyltransferase, the enzyme catalyzing the first and rate-limiting step in de novo sphingolipid biosynthesis, and mutations in this gene are known to cause hereditary sensory autonomic neuropathy, type 1A. Using exome sequencing, we identified a de novo variant in SPTLC1 resulting in a p.Ala20Ser amino acid change in an individual diagnosed with juvenile-onset amyotrophic lateral sclerosis (ALS) and confirmed its pathogenicity by showing elevated plasma levels of neurotoxic deoxymethyl-sphinganine. A second case of juvenile-onset ALS arising again from a p.Ala20Ser mutation was later identified, confirming the association of SPTLC1 with this form of motor neuron disease. We also found SPTLC1 mutations in 0.34% of 5,607 ALS cases, and immunohistochemically confirmed the expression of SPTLC1 in spinal cord motor neurons, supporting their role in the pathogenesis of this fatal neurological disease. We corrected the toxicity of deoxymethyl-sphinganine in HEK293FT cells using L-serine supplementation. Our data broaden the phenotype associated with SPTLC1 and suggest that nutritional supplementation with serine may be beneficial if instituted at an early stage among patients carrying mutations in SPTLC1.
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Brief Communications Overexpression of the Wild-Type SPT1 Subunit Lowers Desoxysphingolipid Levels and Rescues the Phenotype
2015Co-Authors: Of Hsan, Robert H. BrownAbstract:Mutations in the SPTLC1 subunit of serine palmitoyltransferase (SPT) cause an adult-onset, hereditary sensory, and autonomic neurop-athy type I (HSAN1). We previously reported that mice bearing a transgene-expressingmutant SPTLC1 (tgSPTLC1C133W) show a reduc-tion in SPT activity and hyperpathia at 10months of age. Now analyzed at a later age, we find thesemice develop sensory losswith a distal small fiber neuropathy and peripheral myelinopathy. This phenotype is largely reversed when these mice are crossed with transgenic mice overexpressing wild-type SPTLC1 showing that the mutant SPTLC1 protein is not inherently toxic. Simple loss of SPT activity also cannot account for the HSAN1 phenotype, since heterozygous SPTLC1 knock-out mice have reduced SPT activity but are otherwise normal. Rather, the presence of two newly identified, potentially deleterious deoxysphingoid bases in the tgSPTLC1C133W, but not in th
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oral l serine supplementation reduces production of neurotoxic deoxysphingolipids in mice and humans with hereditary sensory autonomic neuropathy type 1
Journal of Clinical Investigation, 2011Co-Authors: Kevin Garofalo, Thorsten Hornemann, Anke Penno, Arnold Von Eckardstein, Matthew P. Frosch, Robert H. Brown, B P Schmidt, Florian EichlerAbstract:Hereditary sensory and autonomic neuropathy type 1 (HSAN1) causes sensory loss that predominantly affects the lower limbs, often preceded by hyperpathia and spontaneous shooting or lancinating pain. It is caused by several missense mutations in the genes encoding 2 of the 3 subunits of the enzyme serine palmitoyltransferase (SPT). The mutant forms of the enzyme show a shift from their canonical substrate l-serine to the alternative substrate l-alanine. This shift leads to increased formation of neurotoxic deoxysphingolipids (dSLs). Our initial analysis showed that in HEK cells transfected with SPTLC1 mutants, dSL generation was modulated in vitro in the presence of various amino acids. We therefore examined whether in vivo specific amino acid substrate supplementation influenced dSL levels and disease severity in HSAN1. In mice bearing a transgene expressing the C133W SPTLC1 mutant linked to HSAN1, a 10% l-serine–enriched diet reduced dSL levels. l-serine supplementation also improved measures of motor and sensory performance as well as measures of male fertility. In contrast, a 10% l-alanine–enriched diet increased dSL levels and led to severe peripheral neuropathy. In a pilot study with 14 HSAN1 patients, l-serine supplementation similarly reduced dSL levels. These observations support the hypothesis that an altered substrate selectivity of the mutant SPT is key to the pathophysiology of HSAN1 and raise the prospect of l-serine supplementation as a first treatment option for this disorder.
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hereditary sensory neuropathy type 1 is caused by the accumulation of two neurotoxic sphingolipids
Journal of Biological Chemistry, 2010Co-Authors: Anke Penno, MM Reilly, Garth A. Nicholson, M Laura, Henry Houlden, Katharina Rentsch, Vera Niederkofler, Esther T Stoeckli, Florian Eichler, Robert H. BrownAbstract:HSAN1 is an inherited neuropathy found to be associated with several missense mutations in the SPTLC1 subunit of serine palmitoyltransferase (SPT). SPT catalyzes the condensation of serine and palmitoyl-CoA, the initial step in the de novo synthesis of sphingolipids. Here we show that the HSAN1 mutations induce a shift in the substrate specificity of SPT, which leads to the formation of the two atypical deoxy-sphingoid bases (DSBs) 1-deoxy-sphinganine and 1-deoxymethyl-sphinganine. Both metabolites lack the C(1) hydroxyl group of sphinganine and can therefore neither be converted to complex sphingolipids nor degraded. Consequently, they accumulate in the cell, as demonstrated in HEK293 cells overexpressing mutant SPTLC1 and lymphoblasts of HSAN1 patients. Elevated DSB levels were also found in the plasma of HSAN1 patients and confirmed in three groups of HSAN1 patients with different SPTLC1 mutations. The DSBs show pronounced neurotoxic effects on neurite formation in cultured sensory neurons. The neurotoxicity co-occurs with a disturbed neurofilament structure in neurites when cultured in the presence of DSBs. Based on these observations, we conclude that HSAN1 is caused by a gain of function mutation, which results in the formation of two atypical and neurotoxic sphingolipid metabolites.
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SPTLC1 is mutated in hereditary sensory neuropathy, type 1
Nature genetics, 2001Co-Authors: Khemissa Bejaoui, Margaret D. Scheffler, Geoffry Haan, Peter Ashby, Peter De Jong, Robert H. BrownAbstract:Hereditary sensory neuropathy type 1 (HSN1, MIM 162400; ref. 1) genetically maps to human chromosome 9q22 (refs. 2-4). We report here that the gene encoding a subunit of serine palmitoyltransferase is located within the HSN1 locus, expressed in dorsal root ganglia (DRG) and mutated in HSN1.