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Michel Marcil - One of the best experts on this subject based on the ideXlab platform.

  • Sphingomyelin Phosphodiesterase 1 smpd1 coding variants do not contribute to low levels of high density lipoprotein cholesterol
    BMC Medical Genetics, 2007
    Co-Authors: Zari Dastani, Isabelle Ruel, James C Engert, Jacques Genest, Michel Marcil
    Abstract:

    Niemann-Pick disease type A and B is caused by a deficiency of acid Sphingomyelinase due to mutations in the Sphingomyelin Phosphodiesterase-1 (SMPD1) gene. In Niemann-Pick patients, SMPD1 gene defects are reported to be associated with a severe reduction in plasma high-density lipoprotein (HDL) cholesterol. Two common coding polymorphisms in the SMPD1 gene, the G1522A (G508R) and a hexanucleotide repeat sequence within the signal peptide region, were investigated in 118 unrelated subjects of French Canadian descent with low plasma levels of HDL-cholesterol ( the 25th percentile. For G1522A the frequency of the G and A alleles were 75.2% and 24.8% respectively in controls, compared to 78.6% and 21.4% in subjects with low HDL-cholesterol (p = 0.317). The frequency of 6 and 7 hexanucleotide repeats was 46.2% and 46.6% respectively in controls, compared to 45.6% and 49.1% in subjects with low HDL-cholesterol (p = 0.619). Ten different haplotypes were observed in cases and controls. Overall haplotype frequencies in cases and controls were not significantly different. These results suggest that the two common coding variants at the SMPD1 gene locus are not associated with low HDL-cholesterol levels in the French Canadian population.

  • compound heterozygosity at the Sphingomyelin Phosphodiesterase 1 smpd1 gene is associated with low hdl cholesterol
    Human Genetics, 2003
    Co-Authors: Jacques Genest, Michel Marcil, Ching Yin Lee, Larbi Krimbou, Jerome Vincent, Chantal Bernard, Pierre Larramee
    Abstract:

    Type A and B forms of Niemann-Pick disease (NPD) are lipid storage disorders caused by deficient activity of the enzyme acid Sphingomyelinase (aSMase) and the resulting accumulation of Sphingomyelin in tissues. In the present study, we investigated two family members who had been diagnosed with Type B NPD and who had a severe decrease in plasma high density lipoprotein cholesterol (HDL-C). The proband (a 48-year-old male) had an HDL-C of 0.30 mmol/l (12 mg/dl) and his sister had values of 0.45 mmol/l (17 mg/dl) with severe premature coronary artery disease (CAD). Hypertriglyceridemia was found in both cases. aSMase activity measured in skin fibroblasts appeared markedly depressed. The SMPD1 gene, coding for aSMase, was sequenced in affected subjects and all family members. Compound heterozygosity (DeltaR608 and R441X) was identified in both affected patients. Carriers of the DeltaR608 mutation tended to have moderately to severe decreased HDL-C levels, whereas carriers of the R441X mutation, although present only in young subjects (<20 years of age) had normal HDL-C levels. To investigate the cause of the low HDL-C level in these patients, we studied apoA-I-mediated cellular cholesterol efflux in fibroblasts. Unlike patients with Tangier disease, cholesterol efflux was found to be normal under the experimental conditions used in the present study. On the other hand, we observed a significant increase in the free cholesterol:esterified cholesterol ratio in HDL fraction from these patients and a decrease in endogenous lecithin-cholesterol acyltransferase (LCAT) activity, as determined by the fractional esterification rate. Taken together, these results suggest that (1) compound heterozygosity at the SMPD1 gene causes a severe decrease in aSMase activity and in HDL-C and increases the risk of CAD, (2) this lipoprotein abnormality is not attributable to defective cellular cholesterol efflux, (3) abnormal HDL composition might cause a decrease in LCAT activity and a lack of HDL maturation.

Leonard Kritharides - One of the best experts on this subject based on the ideXlab platform.

  • n glycosylation of human Sphingomyelin Phosphodiesterase acid like 3a smpdl3a is essential for stability secretion and activity
    Biochemical Journal, 2017
    Co-Authors: Mathew Traini, Raani Yogeeta A Kumaran, Morten Thaysenandersen, Maaike Kockx, Wendy Jessup, Leonard Kritharides
    Abstract:

    Sphingomyelin Phosphodiesterase acid-like 3A (SMPDL3A) is a recently identified Phosphodiesterase, which is a secreted N -linked glycoprotein. SMPDL3A is highly homologous to acid Sphingomyelinase (aSMase), but unlike aSMase cannot cleave Sphingomyelin. Rather, SMPDL3A hydrolyzes nucleotide tri- and diphosphates and their derivatives. While recent structural studies have shed light on these unexpected substrate preferences, many other aspects of SMPDL3A biology, which may give insight into its function in vivo , remain obscure. Here, we investigate the roles of N-glycosylation in the expression, secretion and activity of human SMPDL3A, using inhibitors of N-glycosylation and site-directed mutagenesis, with either THP-1 macrophages or CHO cells expressing human SMPDL3A. Tunicamycin (TM) treatment resulted in expression of non-glycosylated SMPDL3A that was not secreted, and was largely degraded by the proteasome. Proteasomal inhibition restored levels of SMPDL3A in TM-treated cells, although this non-glycosylated protein lacked Phosphodiesterase activity. Enzymatic deglycosylation of purified recombinant SMPDL3A also resulted in significant loss of Phosphodiesterase activity. Site-directed mutagenesis of individual N-glycosylation sites in SMPDL3A identified glycosylation of Asn69 and Asn222 as affecting maturation of its N -glycans and secretion. Glycosylation of Asn356 in SMPDL3A, an N- linked site conserved throughout the aSMase-like family, was critical for protection against proteasomal degradation and preservation of enzymatic activity. We provide the first experimental evidence for a predicted 22 residue N-terminal signal peptide in SMPDL3A, which is essential for facilitating glycosylation and is removed from the mature protein secreted from CHO cells. In conclusion, site-specific N-glycosylation is essential for the intracellular stability, secretion and activity of human SMPDL3A. * aSMase, : acid Sphingomyelinase; BiP, : binding immunoglobulin protein; bis- p NPP, : bis- p -nitrophenylphosphate; BSA, : bovine serum albumin; CDP, : cytidine diphosphate; CHO, : Chinese hamster ovary; CID, : collision-induced dissociation; CST, : castanospermine; DBC1, : deleted in bladder cancer protein 1; DMJ, : deoxymannojirimycin; DTT, : dithiothreitol; Endo H, : endoglycosidase H; ER, : endoplasmic reticulum; ETD, : electron transfer dissociation; IL-6, : interleukin 6; LC, : liquid chromatography; LXR, : liver-X-receptor; MG132, : benzyloxycarbonyl-Leu-Leu-Leu-al; MS, : tandem mass spectrometry; M6P, : mannose-6-phosphate; PBS, : phosphate buffered saline; PCR, : polymerase chain reaction; PMA, : phorbol 12-myristate 13-acetate; PNGase F, : peptide: N- glycosidase F; SDS, : sodium dodecylsulfate; SMPDL3A, : Sphingomyelin Phosphodiesterase acid-like 3A; SMPDL3B, : Sphingomyelin Phosphodiesterase acid-like 3B; SWN, : swainsonine; T-09, : T-0901317; TM, : tunicamycin.

  • Sphingomyelin Phosphodiesterase acid like 3a smpdl3a is a novel nucleotide Phosphodiesterase regulated by cholesterol in human macrophages
    Journal of Biological Chemistry, 2014
    Co-Authors: Mathew Traini, Maaike Kockx, Wendy Jessup, Carmel M Quinn, Cecilia Sandoval, Erik Johansson, Kate Schroder, Peter J Meikle, Leonard Kritharides
    Abstract:

    Cholesterol-loaded foam cell macrophages are prominent in atherosclerotic lesions and play complex roles in both inflammatory signaling and lipid metabolism, which are underpinned by large scale reprogramming of gene expression. We performed a microarray study of primary human macrophages that showed that transcription of the Sphingomyelin Phosphodiesterase acid-like 3A (SMPDL3A) gene is up-regulated after cholesterol loading. SMPDL3A protein expression in and secretion from primary macrophages are stimulated by cholesterol loading, liver X receptor ligands, and cyclic AMP, and N-glycosylated SMPDL3A protein is detectable in circulating blood. We demonstrate for the first time that SMPDL3A is a functional Phosphodiesterase with an acidic pH optimum. We provide evidence that SMPDL3A is not an acid Sphingomyelinase but unexpectedly is active against nucleotide diphosphate and triphosphate substrates at acidic and neutral pH. SMPDL3A is a major source of nucleotide Phosphodiesterase activity secreted by liver X receptor-stimulated human macrophages. Extracellular nucleotides such as ATP may activate pro-inflammatory responses in immune cells. Increased expression and secretion of SMPDL3A by cholesterol-loaded macrophage foam cells in lesions may decrease local concentrations of pro-inflammatory nucleotides and potentially represent a novel anti-inflammatory axis linking lipid metabolism with purinergic signaling in atherosclerosis.

Uladzislau Rudakou - One of the best experts on this subject based on the ideXlab platform.

  • smpd1 variants do not have a major role in rapid eye movement sleep behavior disorder
    Neurobiology of Aging, 2020
    Co-Authors: Jennifer Ruskey, Uladzislau Rudakou, Naomi C Futhey, Lynne Krohn, Karl Heilbron, Paul Cannon, Armaghan Alam
    Abstract:

    Abstract Mutations in the Sphingomyelin Phosphodiesterase 1 (SMPD1) gene were reported to be associated with Parkinson’s disease and dementia with Lewy bodies. In the current study, we aimed to evaluate the role of SMPD1 variants in isolated rapid eye movement sleep behavior disorder (iRBD). SMPD1 and its untranslated regions were sequenced using targeted next-generation sequencing in 959 iRBD patients and 1287 controls from European descent. Our study reports no statistically significant association of SMPD1 variants and iRBD. It is hence unlikely that SMPD1 plays a major role in iRBD.

  • smpd1 variants do not have a major role in rem sleep behavior disorder
    medRxiv, 2020
    Co-Authors: Uladzislau Rudakou, Isabelle Arnulf, Jacques Montplaisir, Jennifer Ruskey, Naomi C Futhey, Lynne Krohn, Karl Heilbron, Paul Cannon, Armaghan Alam, Jean-françois Gagnon
    Abstract:

    Mutations in the Sphingomyelin Phosphodiesterase 1 (SMPD1) gene were reported to be associated with Parkinson disease (PD) and dementia with Lewy bodies (DLB). The majority of patients with isolated rapid eye movement sleep behavior disorder (iRBD) develop PD or DLB later in life, suggesting that iRBD is a prodromal phase of these two conditions. In the current study we aimed to evaluate the role of SMPD1 variants in iRBD. SMPD1 and its untranslated regions were sequenced using targeted next-generation sequencing in 959 iRBD patients and 1,287 controls from European descent. Logistic regression adjusted for sex and age showed no significant associations with two common variants and iRBD (rs1050239 and rs8164). The frequency of all rare nonsynonymous SMPD1 variants (minor allele frequency <1%) was found to be twice as high in cases than in controls (1.46% vs. 0.70%, Fisher's exact test p=0.09) but there was no statistically significant burden (p=0.64). Our study reports no statistically significant association of SMPD1 variants and iRBD. It is hence unlikely that SMPD1 plays a major role in iRBD.

Par Nordlund - One of the best experts on this subject based on the ideXlab platform.

  • the structure and catalytic mechanism of human Sphingomyelin Phosphodiesterase like 3a an acid Sphingomyelinase homologue with a novel nucleotide hydrolase activity
    FEBS Journal, 2016
    Co-Authors: Sing Mei Lim, Kit Yeung, Lionel Tresaugues, Teo Hsiang Ling, Par Nordlund
    Abstract:

    Human Sphingomyelinase Phosphodiesterase like 3a (SMPDL3a) is a secreted enzyme that shares a conserved catalytic domain with human acid Sphingomyelinase (aSMase), the enzyme carrying mutations causative of Niemann–Pick disease. We have solved the structure of SMPDL3a revealing a calcineurin-like fold. A dimetal site, glycosylation pattern and a disulfide bond network are likely to be conserved also in human aSMase. We show that the binuclear site of SMPDL3a is occupied by two Zn2+ ions and that excess Zn2+ leads to inhibition of enzyme activity through binding to additional sites. As an extension of recent biochemical work we uncovered that SMPDL3a catalyses the hydrolysis of several modified nucleotides that include cytidine 5′-diphosphocholine, cytidine diphosphate ethanolamine and ADP-ribose, but not the aSMase substrate, Sphingomyelin. We subsequently determined the structure of SMPDL3a in complex with the product 5′-cytidine monophosphate (CMP), a structure that is consistent with several distinct coordination modes of the substrate/product in the active site during the reaction cycle. Based on the structure of CMP complexes, we propose a phosphoryl transfer mechanism for SMPDL3a. Finally, a homology model of human aSMase was constructed to allow for the mapping of selected Niemann–Pick disease mutations on a three-dimensional framework to guide further characterization of their effects on aSMase function. Database Structural data are available in the PDB database under the accession numbers 5EBB and 5EBE.

Monzur Murshed - One of the best experts on this subject based on the ideXlab platform.

  • Therapeutic Discovery Off-Target Function of the Sonic Hedgehog Inhibitor Cyclopamine in Mediating Apoptosis via Nitric Oxide– Dependent Neutral Sphingomyelinase 2/Ceramide Induction
    2016
    Co-Authors: Marisa Meyers-needham, Jocelyn A. Lewis, Salih Gencer, Saha A Saddoughi, David R. Sentelle, Jacqueline M. Kraveka, Zohreh Khav, Monzur Murshed, Ozgur M. Cevik, Besim Ogretmen
    Abstract:

    Sonic hedgehog (SHh) signaling is important in the pathogenesis of various human cancers, such as medulloblastomas, and it has been identified as a valid target for anticancer therapeutics. The SHh inhibitor cyclopamine induces apoptosis. The bioactive sphingolipid ceramide mediates cell death in response to various chemotherapeutic agents; however, ceramide’s roles/mechanisms in cyclopamine-induced apoptosis are unknown. Here, we report that cyclopamine mediates ceramide generation selectively via induction of neutral Sphingomyelin Phosphodiesterase 3, SMPD3 (nSMase2) in Daoy human medulloblastoma cells. Importantly, short interfering RNA-mediated knockdown of nSMase2 prevented cyclopamine-induced ceramide generation and protected Daoy cells from drug-induced apoptosis. Accordingly, ectopic wild-type N-SMase2 caused cell death, compared with controls, which express the catalytically inactive N-SMase2 mutant. Interestingly, knockdown of smoothened (Smo), a target protein for cyclopamine, or Gli1, a down-stream signaling transcription factor of Smo, did not affect nSMase2. Mechanistically, our data showed that cyclopamine induced nSMase2 and cell death selectively via increased nitric oxide (NO) generation by neuronal-nitric oxide synthase (n-NOS) induction, in Daoy medulloblastoma, and multiple other human cancer cell lines. Knockdown of n-NOS prevented nSMase2 induction and cell death in response to cyclo-pamine. Accordingly, N-SMase2 activity-deficient skin fibroblasts isolated from homozygous fro/fro (fragi-litas ossium) mice exhibited resistance to NO-induced cell death. Thus, our data suggest a novel off-target function of cyclopamine in inducing apoptosis, at least in part, by n-NOS/NO-dependent induction of N-SMase2/ceramide axis, independent of Smo/Gli inhibition. Mol Cancer Ther; 11(5); 1092–102. 2012 AACR

  • Sphingolipid metabolism and its role in the skeletal tissues
    Cellular and Molecular Life Sciences, 2015
    Co-Authors: Zohreh Khavandgar, Monzur Murshed
    Abstract:

    The regulators affecting skeletal tissue formation and its maintenance include a wide array of molecules with very diverse functions. More recently, sphingolipids have been added to this growing list of regulatory molecules in the skeletal tissues. Sphingolipids are integral parts of various lipid membranes present in the cells and organelles. For a long time, these macromolecules were considered as inert structural elements. This view, however, has radically changed in recent years as sphingolipids are now recognized as important second messengers for signal-transduction pathways that affect cell growth, differentiation, stress responses and programmed death. In the current review, we discuss the available data showing the roles of various sphingolipids in three different skeletal cell types—chondrocytes in cartilage and osteoblasts and osteoclasts in bone. We provide an overview of the biology of Sphingomyelin Phosphodiesterase 3 (SMPD3), an important regulator of sphingolipid metabolism in the skeleton. SMPD3 is localized in the plasma membrane and has been shown to cleave Sphingomyelin to generate ceramide, a bioactive lipid second messenger, and phosphocholine, an essential nutrient. SMPD3 deficiency in mice impairs the mineralization in both cartilage and bone extracellular matrices leading to severe skeletal deformities. A detailed understanding of SMPD3 function may provide a novel insight on the role of sphingolipids in the skeletal tissues.

  • local regulation of tooth mineralization by Sphingomyelin Phosphodiesterase 3
    Journal of Dental Research, 2013
    Co-Authors: Zohreh Khavandgar, Sharifa Alebrahim, Hazem Eimar, Faleh Tamimi, Marc D Mckee, Monzur Murshed
    Abstract:

    Sphingomyelin Phosphodiesterase 3 (Smpd3) encodes a membrane-bound enzyme that cleaves Sphingomyelin to generate several bioactive metabolites. A recessive mutation called fragilitas ossium (fro) in the Smpd3 gene leads to impaired mineralization of bone and tooth extracellular matrix (ECM) in fro/fro mice. In teeth from fro/fro mice at various neonatal ages, radiography and light and electron microscopy showed delayed mantle dentin mineralization and a consequent delay in enamel formation as compared with that in control +/fro mice. These tooth abnormalities progressively improved with time. Immunohistochemistry showed expression of SMPD3 by dentin-forming odontoblasts. SMPD3 deficiency, however, did not affect the differentiation of these cells, as shown by osterix and dentin sialophosphoprotein expression. Using a transgenic mouse rescue model (fro/fro; Col1a1-Smpd3) in which Smpd3 expression is driven by a murine Col1a1 promoter fragment active in osteoblasts and odontoblasts, we demonstrate a complete correction of the tooth mineralization delays. In conclusion, analysis of these data demonstrates that Smpd3 expression in odontoblasts is required for tooth mineralization.