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Yoo SW, Waheed AA, Deme P, Tohumeken S, Rais R, Smith MD, DeMarino C, Calabresi PA, Kashanchi F, Freed EO, Slusher BS, Haughey NJ. Inhibition of neutral sphingomyelinase 2 impairs HIV-1 envelope formation and substantially delays or eliminates viral rebound. Proc Natl Acad Sci U S A 2023; 120:e2219543120. [PMID: 37406092 PMCID: PMC10334757 DOI: 10.1073/pnas.2219543120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Accepted: 04/03/2023] [Indexed: 07/07/2023] Open
Abstract
Although HIV-1 Gag is known to drive viral assembly and budding, the precise mechanisms by which the lipid composition of the plasma membrane is remodeled during assembly are incompletely understood. Here, we provide evidence that the sphingomyelin hydrolase neutral sphingomyelinase 2 (nSMase2) interacts with HIV-1 Gag and through the hydrolysis of sphingomyelin creates ceramide that is necessary for proper formation of the viral envelope and viral maturation. Inhibition or depletion of nSMase2 resulted in the production of noninfectious HIV-1 virions with incomplete Gag lattices lacking condensed conical cores. Inhibition of nSMase2 in HIV-1-infected humanized mouse models with a potent and selective inhibitor of nSMase2 termed PDDC [phenyl(R)-(1-(3-(3,4-dimethoxyphenyl)-2, 6-dimethylimidazo[1,2-b]pyridazin-8-yl) pyrrolidin-3-yl)-carbamate] produced a linear reduction in levels of HIV-1 in plasma. If undetectable plasma levels of HIV-1 were achieved with PDDC treatment, viral rebound did not occur for up to 4 wk when PDDC was discontinued. In vivo and tissue culture results suggest that PDDC selectively kills cells with actively replicating HIV-1. Collectively, this work demonstrates that nSMase2 is a critical regulator of HIV-1 replication and suggests that nSMase2 could be an important therapeutic target with the potential to kill HIV-1-infected cells.
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Affiliation(s)
- Seung-Wan Yoo
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD21210
| | - Abdul A. Waheed
- Virus-Cell Interaction Section, HIV-1 Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute-Frederick, Frederick, MD21702
| | - Pragney Deme
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD21210
| | - Sehmus Tohumeken
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD21210
| | - Rana Rais
- Johns Hopkins Drug Discovery, Johns Hopkins University School of Medicine, Baltimore, MD21205
| | - Matthew D. Smith
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD21210
| | - Catherine DeMarino
- Laboratory of Molecular Virology, George Mason University, Manassas, VA20110
| | - Peter A. Calabresi
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD21210
| | - Fatah Kashanchi
- Laboratory of Molecular Virology, George Mason University, Manassas, VA20110
| | - Eric O. Freed
- Virus-Cell Interaction Section, HIV-1 Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute-Frederick, Frederick, MD21702
| | - Barbara S. Slusher
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD21210
- Johns Hopkins Drug Discovery, Johns Hopkins University School of Medicine, Baltimore, MD21205
- Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD21210
- Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, MD21210
- Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD21224
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD21205
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD21210
| | - Norman J. Haughey
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD21210
- Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, MD21210
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2
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Planas-Serra L, Launay N, Goicoechea L, Heron B, Jou C, Juliá-Palacios N, Ruiz M, Fourcade S, Casasnovas C, De La Torre C, Gelot A, Marsal M, Loza-Alvarez P, García-Cazorla À, Fatemi A, Ferrer I, Portero-Otin M, Area-Gómez E, Pujol A. Sphingolipid desaturase DEGS1 is essential for mitochondria-associated membrane integrity. J Clin Invest 2023; 133:e162957. [PMID: 36951944 PMCID: PMC10178845 DOI: 10.1172/jci162957] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Accepted: 03/22/2023] [Indexed: 03/24/2023] Open
Abstract
Sphingolipids function as membrane constituents and signaling molecules, with crucial roles in human diseases, from neurodevelopmental disorders to cancer, best exemplified in the inborn errors of sphingolipid metabolism in lysosomes. The dihydroceramide desaturase Δ4-dihydroceramide desaturase 1 (DEGS1) acts in the last step of a sector of the sphingolipid pathway, de novo ceramide biosynthesis. Defects in DEGS1 cause the recently described hypomyelinating leukodystrophy-18 (HLD18) (OMIM #618404). Here, we reveal that DEGS1 is a mitochondria-associated endoplasmic reticulum membrane-resident (MAM-resident) enzyme, refining previous reports locating DEGS1 at the endoplasmic reticulum only. Using patient fibroblasts, multiomics, and enzymatic assays, we show that DEGS1 deficiency disrupts the main core functions of the MAM: (a) mitochondrial dynamics, with a hyperfused mitochondrial network associated with decreased activation of dynamin-related protein 1; (b) cholesterol metabolism, with impaired sterol O-acyltransferase activity and decreased cholesteryl esters; (c) phospholipid metabolism, with increased phosphatidic acid and phosphatidylserine and decreased phosphatidylethanolamine; and (d) biogenesis of lipid droplets, with increased size and numbers. Moreover, we detected increased mitochondrial superoxide species production in fibroblasts and mitochondrial respiration impairment in patient muscle biopsy tissues. Our findings shed light on the pathophysiology of HLD18 and broaden our understanding of the role of sphingolipid metabolism in MAM function.
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Affiliation(s)
- Laura Planas-Serra
- Neurometabolic Diseases Laboratory, Bellvitge Biomedical Research Institute (IDIBELL), L’Hospitalet de Llobregat, Barcelona, Catalonia, Spain
- Centre for Biomedical Research on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
| | - Nathalie Launay
- Neurometabolic Diseases Laboratory, Bellvitge Biomedical Research Institute (IDIBELL), L’Hospitalet de Llobregat, Barcelona, Catalonia, Spain
- Centre for Biomedical Research on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
| | - Leire Goicoechea
- Neurometabolic Diseases Laboratory, Bellvitge Biomedical Research Institute (IDIBELL), L’Hospitalet de Llobregat, Barcelona, Catalonia, Spain
- Centre for Biomedical Research on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
| | - Bénédicte Heron
- Department of Paediatric Neurology, Reference Centre for Neurogenetic Diseases, Armand Trousseau–La Roche Guyon University Hospital, and I2-D2 Federation, Sorbonne-Université, Paris, France
| | - Cristina Jou
- Centre for Biomedical Research on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
- Neurometabolic Unit and Synaptic Metabolism Lab, Neurology and Pathology Department, Institut Pediàtric de Recerca, Hospital Sant Joan de Déu, and MetabERN, Barcelona, Catalonia, Spain
| | - Natalia Juliá-Palacios
- Neurometabolic Unit and Synaptic Metabolism Lab, Neurology and Pathology Department, Institut Pediàtric de Recerca, Hospital Sant Joan de Déu, and MetabERN, Barcelona, Catalonia, Spain
| | - Montserrat Ruiz
- Neurometabolic Diseases Laboratory, Bellvitge Biomedical Research Institute (IDIBELL), L’Hospitalet de Llobregat, Barcelona, Catalonia, Spain
- Centre for Biomedical Research on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
| | - Stéphane Fourcade
- Neurometabolic Diseases Laboratory, Bellvitge Biomedical Research Institute (IDIBELL), L’Hospitalet de Llobregat, Barcelona, Catalonia, Spain
- Centre for Biomedical Research on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
| | - Carlos Casasnovas
- Neurometabolic Diseases Laboratory, Bellvitge Biomedical Research Institute (IDIBELL), L’Hospitalet de Llobregat, Barcelona, Catalonia, Spain
- Centre for Biomedical Research on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
- Neuromuscular Unit, Neurology Department, Hospital Universitari de Bellvitge, Universitat de Barcelona, L’Hospitalet de Llobregat, Barcelona, Catalonia, Spain
| | | | - Antoinette Gelot
- Armand Trousseau–La Roche Guyon University Hospital, Sorbonne-Université, Paris, France
| | - Maria Marsal
- ICFO–Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona, Catalonia, Spain
| | - Pablo Loza-Alvarez
- ICFO–Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona, Catalonia, Spain
| | - Àngels García-Cazorla
- Centre for Biomedical Research on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
- Neurometabolic Unit and Synaptic Metabolism Lab, Neurology and Pathology Department, Institut Pediàtric de Recerca, Hospital Sant Joan de Déu, and MetabERN, Barcelona, Catalonia, Spain
| | - Ali Fatemi
- Departments of Neurology and Pediatrics, The Kennedy Krieger Institute, and Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Isidre Ferrer
- Department of Pathology and Experimental Therapeutics, University of Barcelona, L’Hospitalet de Llobregat, Barcelona, Catalonia, Spain
- Network Centre of Biomedical Research of Neurodegenerative Diseases (CIBERNED), Institute of Health Carlos III, L’Hospitalet de Llobregat, Barcelona, Catalonia, Spain
| | - Manel Portero-Otin
- Departament de Medicina Experimental, Universitat de Lleida–Institut de Recerca Biomedica de Lleida, Lleida, Catalonia, Spain
| | - Estela Area-Gómez
- Department of Neurology, Columbia University Medical Center, New York, New York, USA
- Centro de Investigaciones Biológicas “Margarita Salas,” Madrid, Spain
| | - Aurora Pujol
- Neurometabolic Diseases Laboratory, Bellvitge Biomedical Research Institute (IDIBELL), L’Hospitalet de Llobregat, Barcelona, Catalonia, Spain
- Centre for Biomedical Research on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
- Catalan Institution of Research and Advanced Studies (ICREA), Barcelona, Catalonia, Spain
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3
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Tohumeken S, Deme P, Yoo SW, Gupta S, Rais R, Slusher BS, Haughey NJ. Neuronal deletion of nSMase2 reduces the production of Aβ and directly protects neurons. Neurobiol Dis 2023; 177:105987. [PMID: 36603748 DOI: 10.1016/j.nbd.2023.105987] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Revised: 12/28/2022] [Accepted: 01/01/2023] [Indexed: 01/03/2023] Open
Abstract
Extracellular vesicles (EVs) have been proposed to regulate the deposition of Aβ. Multiple publications have shown that APP, amyloid processing enzymes and Aβ peptides are associated with EVs. However, very little Aβ is associated with EVs compared with the total amount Aβ present in human plasma, CSF, or supernatants from cultured neurons. The involvement of EVs has largely been inferred by pharmacological inhibition or whole body deletion of the sphingomyelin hydrolase neutral sphingomyelinase-2 (nSMase2) that is a key regulator for the biogenesis of at-least one population of EVs. Here we used a Cre-Lox system to selectively delete nSMase2 from pyramidal neurons in APP/PS1 mice (APP/PS1-SMPD3-Nex1) and found a ∼ 70% reduction in Aβ deposition at 6 months of age and ∼ 35% reduction at 12 months of age in both cortex and hippocampus. Brain ceramides were increased in APP/PS1 compared with Wt mice, but were similar to Wt in APP/PS1-SMPD3-Nex1 mice suggesting that elevated brain ceramides in this model involves neuronally expressed nSMase2. Reduced levels of PSD95 and deficits of long-term potentiation in APP/PS1 mice were normalized in APP/PS1-SMPD3-Nex1 mice. In contrast, elevated levels of IL-1β, IL-8 and TNFα in APP/PS1 mice were not normalized in APP/PS1-SMPD3-Nex1 mice compared with APP/PS1 mice. Mechanistic studies showed that the size of liquid ordered membrane microdomains was increased in APP/PS1 mice, as were the amounts of APP and BACE1 localized to these microdomains. Pharmacological inhibition of nSMase2 activity with PDDC reduced the size of the liquid ordered membrane microdomains, reduced the localization of APP with BACE1 and reduced the production of Aβ1-40 and Aβ1-42. Although inhibition of nSMase2 reduced the release and increased the size of EVs, very little Aβ was associated with EVs in all conditions tested. We also found that nSMase2 directly protected neurons from the toxic effects of oligomerized Aβ and preserved neural network connectivity despite considerable Aβ deposition. These data demonstrate that nSMase2 plays a role in the production of Aβ by stabilizing the interaction of APP with BACE1 in liquid ordered membrane microdomains, and directly protects neurons from the toxic effects of Aβ. The effects of inhibiting nSMase2 on EV biogenesis may be independent from effects on Aβ production and neuronal protection.
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Affiliation(s)
- Sehmus Tohumeken
- The Johns Hopkins University School of Medicine, Departments of Neurology, United States of America
| | - Pragney Deme
- The Johns Hopkins University School of Medicine, Departments of Neurology, United States of America
| | - Seung Wan Yoo
- The Johns Hopkins University School of Medicine, Departments of Neurology, United States of America
| | - Sujasha Gupta
- The Johns Hopkins University School of Medicine, Departments of Neurology, United States of America
| | - Rana Rais
- The Johns Hopkins University School of Medicine, Departments of Psychiatry, United States of America
| | - Barbara S Slusher
- The Johns Hopkins University School of Medicine, Departments of Neurology, United States of America; The Johns Hopkins University School of Medicine, Departments of Johns Hopkins Drug Discovery, United States of America; The Johns Hopkins University School of Medicine, Departments of Psychiatry, United States of America; The Johns Hopkins University School of Medicine, Departments of Pharmacology and Molecular Sciences, United States of America; The Johns Hopkins University School of Medicine, Departments of Department of Oncology, United States of America; The Johns Hopkins University School of Medicine, Departments of Department of Neuroscience, United States of America; The Johns Hopkins University School of Medicine, Departments of Department of Medicine, Baltimore, MD, United States of America
| | - Norman J Haughey
- The Johns Hopkins University School of Medicine, Departments of Neurology, United States of America; The Johns Hopkins University School of Medicine, Departments of Johns Hopkins Drug Discovery, United States of America.
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Momchilova A, Pankov R, Alexandrov A, Markovska T, Pankov S, Krastev P, Staneva G, Vassileva E, Krastev N, Pinkas A. Sphingolipid Catabolism and Glycerophospholipid Levels Are Altered in Erythrocytes and Plasma from Multiple Sclerosis Patients. Int J Mol Sci 2022; 23:ijms23147592. [PMID: 35886939 PMCID: PMC9315580 DOI: 10.3390/ijms23147592] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2022] [Revised: 07/01/2022] [Accepted: 07/07/2022] [Indexed: 01/27/2023] Open
Abstract
Multiple sclerosis (MS) is an autoimmune, inflammatory, degenerative disease of the central nervous system. Changes in lipid metabolism have been suggested to play important roles in MS pathophysiology and progression. In this work we analyzed the lipid composition and sphingolipid-catabolizing enzymes in erythrocytes and plasma from MS patients and healthy controls. We observed reduction of sphingomyelin (SM) and elevation of its products—ceramide (CER) and shingosine (SPH). These changes were supported by the detected up-regulation of the activity of acid sphingomyelinase (ASM) in MS plasma and alkaline ceramidase (ALCER) in erythrocytes from MS patients. In addition, Western blot analysis showed elevated expression of ASM, but not of ALCER. We also compared the ratios between saturated (SAT), unsaturated (UNSAT) and polyunsaturated fatty acids and suggest, based on the significant differences observed for this ratio, that the UNSAT/SAT values could serve as a marker distinguishing erythrocytes and plasma of MS from controls. In conclusion, the application of lipid analysis in the medical practice would contribute to definition of more precise diagnosis, analysis of disease progression, and evaluation of therapeutic strategies. Based on the molecular changes of blood lipids in neurodegenerative pathologies, including MS, clinical lipidomic analytical approaches could become a promising contemporary tool for personalized medicine.
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Affiliation(s)
- Albena Momchilova
- Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. Bl. 21, 1113 Sofia, Bulgaria; (A.A.); (T.M.); (S.P.); (G.S.)
- Correspondence: ; Tel.: +359-2-9792686 or +359-898-238971
| | - Roumen Pankov
- Biological Faculty, Sofia University, 8, Dragan Tzankov Str., 1164 Sofia, Bulgaria;
| | - Alexander Alexandrov
- Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. Bl. 21, 1113 Sofia, Bulgaria; (A.A.); (T.M.); (S.P.); (G.S.)
| | - Tania Markovska
- Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. Bl. 21, 1113 Sofia, Bulgaria; (A.A.); (T.M.); (S.P.); (G.S.)
| | - Stefan Pankov
- Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. Bl. 21, 1113 Sofia, Bulgaria; (A.A.); (T.M.); (S.P.); (G.S.)
| | - Plamen Krastev
- Cardiology Clinic, University Hospital St. Ekaterina, 1431 Sofia, Bulgaria;
| | - Galya Staneva
- Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. Bl. 21, 1113 Sofia, Bulgaria; (A.A.); (T.M.); (S.P.); (G.S.)
| | - Evgenia Vassileva
- Clinic of Neurology, Tsaritsa Yoanna University Hospital-ISUL, 1527 Sofia, Bulgaria;
| | - Nikolai Krastev
- Department of Anatomy, Histology and Embryology, Medical University-Sofia, Blvd. Sv. Georgi Sofiisky 1, 1431 Sofia, Bulgaria;
- Medical Center Relax, 8 Ami Bue Str., 1606 Sofia, Bulgaria
| | - Adriana Pinkas
- STEP/CSTEP, Office of Continuing Education, Suffolk County Community College 30 Greene Ave., Sayville, NY 11782, USA;
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Philipsen MH, Ranjbari E, Gu C, Ewing AG. Mass Spectrometry Imaging Shows Modafinil, A Student Study Drug, Changes the Lipid Composition of the Fly Brain. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202105004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Mai H. Philipsen
- Department of Chemistry and Molecular Biology University of Gothenburg Kemigården 4 41296 Göteborg Sweden
| | - Elias Ranjbari
- Department of Chemistry and Molecular Biology University of Gothenburg Kemigården 4 41296 Göteborg Sweden
| | - Chaoyi Gu
- Department of Chemistry and Molecular Biology University of Gothenburg Kemigården 4 41296 Göteborg Sweden
| | - Andrew G. Ewing
- Department of Chemistry and Molecular Biology University of Gothenburg Kemigården 4 41296 Göteborg Sweden
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Philipsen MH, Ranjbari E, Gu C, Ewing AG. Mass Spectrometry Imaging Shows Modafinil, A Student Study Drug, Changes the Lipid Composition of the Fly Brain. Angew Chem Int Ed Engl 2021; 60:17378-17382. [PMID: 34041832 PMCID: PMC8361715 DOI: 10.1002/anie.202105004] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Indexed: 12/17/2022]
Abstract
Modafinil, a widely used psychoactive drug, has been shown to exert a positive impact on cognition and is used to treat sleep disorders and hyperactivity. Using time-of-flight secondary ion mass spectrometric imaging, we studied the changes of brain lipids of Drosophila melanogaster induced by modafinil to gain insight into the functional mechanism of modafinil in the brain. We found that upon modafinil treatment, the abundance of phosphatidylcholine and sphingomyelin species in the central brain of Drosophila is significantly decreased, whereas the levels of phosphatidylethanolamine and phosphatidylinositol in the brains show significant enhancement compared to the control flies. The alteration of brain lipids caused by modafinil is consistent with previous studies about cognition-related drugs and offers a plausible mechanism regarding the action of modafinil in the brain as well as a potential target for the treatment of certain disorders.
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Affiliation(s)
- Mai H. Philipsen
- Department of Chemistry and Molecular BiologyUniversity of GothenburgKemigården 441296GöteborgSweden
| | - Elias Ranjbari
- Department of Chemistry and Molecular BiologyUniversity of GothenburgKemigården 441296GöteborgSweden
| | - Chaoyi Gu
- Department of Chemistry and Molecular BiologyUniversity of GothenburgKemigården 441296GöteborgSweden
| | - Andrew G. Ewing
- Department of Chemistry and Molecular BiologyUniversity of GothenburgKemigården 441296GöteborgSweden
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Onset of Senescence and Steatosis in Hepatocytes as a Consequence of a Shift in the Diacylglycerol/Ceramide Balance at the Plasma Membrane. Cells 2021; 10:cells10061278. [PMID: 34064003 PMCID: PMC8224046 DOI: 10.3390/cells10061278] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 05/06/2021] [Accepted: 05/17/2021] [Indexed: 12/17/2022] Open
Abstract
Ceramide and diacylglycerol (DAG) are bioactive lipids and mediate many cellular signaling pathways. Sphingomyelin synthase (SMS) is the single metabolic link between the two, while SMS2 is the only SMS form located at the plasma membrane. SMS2 functions were investigated in HepG2 cell lines stably expressing SMS2. SMS2 overexpression did not alter sphingomyelin (SM), phosphatidylcholine (PC), or ceramide levels. DAG content increased by approx. 40% and led to downregulation of DAG-dependent protein kinase C (PKC). SMS2 overexpression also induced senescence, characterized by positivity for β-galactosidase activity and heterochromatin foci. HepG2-SMS2 cells exhibited protruded mitochondria and suppressed mitochondrial respiration rates. ATP production and the abundance of Complex V were substantially lower in HepG2-SMS2 cells as compared to controls. SMS2 overexpression was associated with inflammasome activation based on increases in IL-1β and nlpr3 mRNA levels. HepG2-SMS2 cells exhibited lipid droplet accumulation, constitutive activation of AMPK based on elevated 172Thr phosphorylation, increased AMPK abundance, and insensitivity to insulin suppression of AMPK. Thus, our results show that SMS2 regulates DAG homeostasis and signaling in hepatocytes and also provide proof of principle for the concept that offset in bioactive lipids’ production at the plasma membrane can drive the senescence program in association with steatosis and, seemingly, by cell-autonomous mechanisms.
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