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Sandvig K, Kavaliauskiene S, Skotland T. Clathrin-independent endocytosis: an increasing degree of complexity. Histochem Cell Biol 2018; 150:107-118. [PMID: 29774430 PMCID: PMC6096564 DOI: 10.1007/s00418-018-1678-5] [Citation(s) in RCA: 106] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/04/2018] [Indexed: 11/03/2022]
Abstract
This article aims at providing an update on the complexity of clathrin-independent endocytosis. It is now almost 30 years since we first wrote a review about its existence; at that time many people believed that with the exception of macropinocytosis, which will only be briefly mentioned in this review, all uptake could be accounted for by clathrin-dependent endocytosis. Now it is generally accepted that there are different clathrin-independent mechanisms, some of them regulated by ligands and membrane lipid composition. They can be both dynamin-dependent and -independent, meaning that the uptake cannot be accounted for by caveolae and other dynamin-dependent processes such as tubular structures that can be induced by toxins, e.g. Shiga toxin, or the fast endophilin mediated endocytosis recently described. Caveolae seem to be mostly quite stable structures with other functions than endocytosis, but evidence suggests that they may have cell-type dependent functions. Although several groups have been working on endocytic mechanisms for years, and new advanced methods have improved our ability to study mechanistic details, there are still a number of important questions we need to address, such as: How many endocytic mechanisms does a cell have? How quantitatively important are they? What about the complexity in polarized cells where clathrin-independent endocytosis is differentially regulated on the apical and basolateral poles? These questions are not easy to answer since one and the same molecule may contribute to more than one process, and manipulating one mechanism can affect another. Also, several inhibitors of endocytic processes commonly used turn out to be less specific than originally thought. We will here describe the current view of clathrin-independent endocytic processes and the challenges in studying them.
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Affiliation(s)
- Kirsten Sandvig
- Department of Molecular Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Montebello, 0379, Oslo, Norway.
- Department of Molecular Biosciences, University of Oslo, 0316, Oslo, Norway.
| | - Simona Kavaliauskiene
- Department of Molecular Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Montebello, 0379, Oslo, Norway
| | - Tore Skotland
- Department of Molecular Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Montebello, 0379, Oslo, Norway
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52
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A hybrid mathematical modeling approach of the metabolic fate of a fluorescent sphingolipid analogue to predict cancer chemosensitivity. Comput Biol Med 2018; 97:8-20. [DOI: 10.1016/j.compbiomed.2018.04.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Revised: 04/10/2018] [Accepted: 04/12/2018] [Indexed: 01/25/2023]
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53
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Abstract
Macroautophagy (herein referred to as autophagy) is a highly conserved stress response that engulfs damaged proteins, lipids, and/or organelles within double-membrane vesicles called autophagosomes for lysosomal degradation. Dysregulated autophagy is a hallmark of cancer; and thus, there is great interest in modulating autophagy for cancer therapy. Sphingolipids regulate each step of autophagosome biogenesis with roles for sphingolipid metabolites and enzymes spanning from the initial step of de novo ceramide synthesis to the sphingosine-1-phosphate lyase 1-mediated exit from the sphingolipid pathway. Notably, sphingolipid metabolism occurs at several of the organelles that contribute to autophagosome biogenesis to suggest that local changes in sphingolipids may regulate autophagy. As sphingolipid metabolism is frequently dysregulated in cancer, a molecular understanding of sphingolipids in stress-induced autophagy may provide insight into the mechanisms driving tumor development and progression. On the contrary, modulation of sphingolipid metabolites and/or enzymes can induce autophagy-dependent cell death for cancer therapy. This chapter will overview the major steps in mammalian autophagy, discuss the regulation of each step by sphingolipid metabolites, and describe the functions of sphingolipid-mediated autophagy in cancer. While our understanding of the signaling and biophysical properties of sphingolipids in autophagy remains in its infancy, the unique cross talk between the two pathways is an exciting area for further development, particularly in the context of cancer therapy.
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Affiliation(s)
- Megan M Young
- Department of Pediatrics, Pennsylvania State University College of Medicine, Hershey, PA, United States
| | - Hong-Gang Wang
- Department of Pediatrics, Pennsylvania State University College of Medicine, Hershey, PA, United States
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54
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Flotillin proteins recruit sphingosine to membranes and maintain cellular sphingosine-1-phosphate levels. PLoS One 2018; 13:e0197401. [PMID: 29787576 PMCID: PMC5963794 DOI: 10.1371/journal.pone.0197401] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Accepted: 04/30/2018] [Indexed: 01/09/2023] Open
Abstract
Sphingosine-1-phosphate (S1P) is an important lipid signalling molecule. S1P is produced via intracellular phosphorylation of sphingosine (Sph). As a lipid with a single fatty alkyl chain, Sph may diffuse rapidly between cellular membranes and through the aqueous phase. Here, we show that the absence of microdomains generated by multimeric assemblies of flotillin proteins results in reduced S1P levels. Cellular phenotypes of flotillin knockout mice, including changes in histone acetylation and expression of Isg15, are recapitulated when S1P synthesis is perturbed. Flotillins bind to Sph in vitro and increase recruitment of Sph to membranes in cells. Ectopic re-localisation of flotillins within the cell causes concomitant redistribution of Sph. The data suggest that flotillins may directly or indirectly regulate cellular sphingolipid distribution and signalling.
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55
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Moruno-Manchon JF, Uzor NE, Ambati CR, Shetty V, Putluri N, Jagannath C, McCullough LD, Tsvetkov AS. Sphingosine kinase 1-associated autophagy differs between neurons and astrocytes. Cell Death Dis 2018; 9:521. [PMID: 29743513 PMCID: PMC5943283 DOI: 10.1038/s41419-018-0599-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Revised: 04/05/2018] [Accepted: 04/12/2018] [Indexed: 02/07/2023]
Abstract
Autophagy is a degradative pathway for removing aggregated proteins, damaged organelles, and parasites. Evidence indicates that autophagic pathways differ between cell types. In neurons, autophagy plays a homeostatic role, compared to a survival mechanism employed by starving non-neuronal cells. We investigated if sphingosine kinase 1 (SK1)-associated autophagy differs between two symbiotic brain cell types-neurons and astrocytes. SK1 synthesizes sphingosine-1-phosphate, which regulates autophagy in non-neuronal cells and in neurons. We found that benzoxazine autophagy inducers upregulate SK1 and neuroprotective autophagy in neurons, but not in astrocytes. Starvation enhances SK1-associated autophagy in astrocytes, but not in neurons. In astrocytes, SK1 is cytoprotective and promotes the degradation of an autophagy substrate, mutant huntingtin, the protein that causes Huntington's disease. Overexpressed SK1 is unexpectedly toxic to neurons, and its toxicity localizes to the neuronal soma, demonstrating an intricate relationship between the localization of SK1's activity and neurotoxicity. Our results underscore the importance of cell type-specific autophagic differences in any efforts to target autophagy therapeutically.
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Affiliation(s)
- Jose F Moruno-Manchon
- Department of Neurobiology and Anatomy, The University of Texas McGovern Medical School, Houston, TX, 77030, USA
| | - Ndidi-Ese Uzor
- Department of Neurobiology and Anatomy, The University of Texas McGovern Medical School, Houston, TX, 77030, USA
- The University of Texas Graduate School of Biomedical Sciences, Houston, TX, 77030, USA
| | - Chandrashekar R Ambati
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Vivekananda Shetty
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Nagireddy Putluri
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Chinnaswamy Jagannath
- Department of Pathology and Laboratory Medicine, The University of Texas McGovern Medical School, Houston, TX, 77030, USA
| | - Louise D McCullough
- The University of Texas Graduate School of Biomedical Sciences, Houston, TX, 77030, USA
- Department of Neurology, The University of Texas McGovern Medical School at Houston, Houston, TX, 77030, USA
| | - Andrey S Tsvetkov
- Department of Neurobiology and Anatomy, The University of Texas McGovern Medical School, Houston, TX, 77030, USA.
- The University of Texas Graduate School of Biomedical Sciences, Houston, TX, 77030, USA.
- UT Health Consortium on Aging, The University of Texas McGovern Medical School, Houston, TX, 77030, USA.
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56
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Di Pardo A, Maglione V. The S1P Axis: New Exciting Route for Treating Huntington's Disease. Trends Pharmacol Sci 2018; 39:468-480. [PMID: 29559169 DOI: 10.1016/j.tips.2018.02.009] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2017] [Revised: 02/22/2018] [Accepted: 02/27/2018] [Indexed: 11/17/2022]
Abstract
Huntington's disease (HD) is a single-gene inheritable neurodegenerative disorder with an associated complex molecular pathogenic profile that renders it the most 'curable incurable' brain disorder. Continuous effort in the field has contributed to the recent discovery of novel potential pathogenic mechanisms. Findings in preclinical models of the disease as well as in human post-mortem brains from affected patients demonstrate that alteration of the sphingosine-1-phosphate (S1P) axis may represent a possible key player in the pathogenesis of the disease and may act as a potential actionable drug target for the development of more targeted and effective therapeutic approaches. The relevance of the path of this new 'therapeutic route' is underscored by the fact that some drugs targeting the S1P axis are currently in clinical trials for the treatment of other brain disorders.
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Affiliation(s)
- Alba Di Pardo
- Centre for Neurogenetics and Rare Diseases, IRCCS Neuromed, 86077 Pozzilli (IS), Italy
| | - Vittorio Maglione
- Centre for Neurogenetics and Rare Diseases, IRCCS Neuromed, 86077 Pozzilli (IS), Italy.
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57
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Hirama T, Fairn GD. Induction of spontaneous curvature and endocytosis: Unwanted consequences of cholesterol extraction using methyl-β-Cyclodextrin. Commun Integr Biol 2018; 11:1-4. [PMID: 30083284 PMCID: PMC6067860 DOI: 10.1080/19420889.2018.1444306] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Accepted: 02/20/2018] [Indexed: 02/06/2023] Open
Abstract
Membrane curvature is a property of biological membranes essential for organelle morphology and the formation of tubulovesicular carriers. Curvature generation is influenced by the lipid composition of the membrane and protein-mediated processes. Lipids with small headgroups, such as phosphatidic acid, are conical and impose negative curvature on a monolayer. Conversely, lipids with large headgroups relative to the hydrophobic tail(s), such as lysophosphatidylcholine, have an inverted conical shape and impose positive curvature. Due to its abundance and high rates of spontaneous flip-flop between membrane leaflets cholesterol is proposed to buffer the formation of membrane curvature. Recently, we demonstrated that cholesterol is also crucial for maintaining the proper spacing of anionic phospholipids. Upon extraction of cholesterol with cyclodextrin there is a sharp increase in the negative surface charge density of the plasma membrane, which promotes electrostatic repulsion between anionic headgroups, the generation of spontaneous positive curvature and rapid membrane internalization.
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Affiliation(s)
- Takashi Hirama
- Division of Respirology, Department of Medicine, University of Toronto, Toronto, ON, Canada.,Program of Lung Transplant, Multi-Organ Transplant Program, Toronto General Hospital, Toronto, ON, Canada.,Nontuberculous Mycobacteria Program, Division of Respirology, Toronto Western Hospital, Toronto, ON, Canada
| | - Gregory D Fairn
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, ON, Canada.,Department of Biochemistry, University of Toronto, Toronto, ON, Canada.,Department of Surgery, University of Toronto, Toronto, ON, Canada
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58
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Stahelin RV. The unmasking of the lipid binding face of sphingosine kinase 1. J Lipid Res 2018; 59:401-403. [DOI: 10.1194/jlr.c083907] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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59
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Abstract
Studies of bioactive lipids in general and sphingolipids in particular have intensified over the past several years, revealing an unprecedented and unanticipated complexity of the lipidome and its many functions, which rivals, if not exceeds, that of the genome or proteome. These results highlight critical roles for bioactive sphingolipids in most, if not all, major cell biological responses, including all major cell signalling pathways, and they link sphingolipid metabolism to key human diseases. Nevertheless, the fairly nascent field of bioactive sphingolipids still faces challenges in its biochemical and molecular underpinnings, including defining the molecular mechanisms of pathway and enzyme regulation, the study of lipid-protein interactions and the development of cellular probes, suitable biomarkers and therapeutic approaches.
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Affiliation(s)
- Yusuf A Hannun
- Stony Brook Cancer Center and Department of Medicine, Stony Brook University, New York 11794, USA
| | - Lina M Obeid
- Stony Brook Cancer Center and Department of Medicine, Stony Brook University, New York 11794, USA
- Northport Veterans Affairs Medical Center, Northport, New York 11768, USA
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60
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Sukocheva OA. Expansion of Sphingosine Kinase and Sphingosine-1-Phosphate Receptor Function in Normal and Cancer Cells: From Membrane Restructuring to Mediation of Estrogen Signaling and Stem Cell Programming. Int J Mol Sci 2018; 19:ijms19020420. [PMID: 29385066 PMCID: PMC5855642 DOI: 10.3390/ijms19020420] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Revised: 01/21/2018] [Accepted: 01/24/2018] [Indexed: 02/05/2023] Open
Abstract
Sphingolipids, sphingolipid metabolizing enzymes, and their receptors network are being recognized as part of the signaling mechanisms, which govern breast cancer cell growth, migration, and survival during chemotherapy treatment. Approximately 70% of breast cancers are estrogen receptor (ER) positive and, thus, rely on estrogen signaling. Estrogen activates an intracellular network composed of many cytoplasmic and nuclear mediators. Some estrogen effects can be mediated by sphingolipids. Estrogen activates sphingosine kinase 1 (SphK1) and amplifies the intracellular concentration of sphingosine-1-phosphate (S1P) in breast cancer cells during stimulation of proliferation and survival. Specifically, Estrogen activates S1P receptors (S1PR) and induces growth factor receptor transactivation. SphK, S1P, and S1PR expression are causally associated with endocrine resistance and progression to advanced tumor stages in ER-positive breast cancers in vivo. Recently, the network of SphK/S1PR was shown to promote the development of ER-negative cancers and breast cancer stem cells, as well as stimulating angiogenesis. Novel findings confirm and broaden our knowledge about the cross-talk between sphingolipids and estrogen network in normal and malignant cells. Current S1PRs therapeutic inhibition was indicated as a promising chemotherapy approach in non-responsive and advanced malignancies. Considering that sphingolipid signaling has a prominent role in terminally differentiated cells, the impact should be considered when designing specific SphK/S1PR inhibitors. This study analyzes the dynamic of the transformation of sphingolipid axis during a transition from normal to pathological condition on the level of the whole organism. The sphingolipid-based mediation and facilitation of global effects of estrogen were critically accented as a bridging mechanism that should be explored in cancer prevention.
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Affiliation(s)
- Olga A Sukocheva
- College of Nursing and Health Sciences, Flinders University of South Australia, Bedford Park, SA 5042, Australia.
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61
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Pulkoski-Gross MJ, Jenkins ML, Truman JP, Salama MF, Clarke CJ, Burke JE, Hannun YA, Obeid LM. An intrinsic lipid-binding interface controls sphingosine kinase 1 function. J Lipid Res 2018; 59:462-474. [PMID: 29326159 DOI: 10.1194/jlr.m081307] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Revised: 01/04/2018] [Indexed: 12/15/2022] Open
Abstract
Sphingosine kinase 1 (SK1) is required for production of sphingosine-1-phosphate (S1P) and thereby regulates many cellular processes, including cellular growth, immune cell trafficking, and inflammation. To produce S1P, SK1 must access sphingosine directly from membranes. However, the molecular mechanisms underlying SK1's direct membrane interactions remain unclear. We used hydrogen/deuterium exchange MS to study interactions of SK1 with membrane vesicles. Using the CRISPR/Cas9 technique to generate HCT116 cells lacking SK1, we explored the effects of membrane interface disruption and the function of the SK1 interaction site. Disrupting the interface resulted in reduced membrane association and decreased cellular SK1 activity. Moreover, SK1-dependent signaling, including cell invasion and endocytosis, was abolished upon mutation of the membrane-binding interface. Of note, we identified a positively charged motif on SK1 that is responsible for electrostatic interactions with membranes. Furthermore, we demonstrated that SK1 uses a single contiguous interface, consisting of an electrostatic site and a hydrophobic site, to interact with membrane-associated anionic phospholipids. Altogether, these results define a composite domain in SK1 that regulates its intrinsic ability to bind membranes and indicate that this binding is critical for proper SK1 function. This work will allow for a new line of thinking for targeting SK1 in disease.
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Affiliation(s)
- Michael J Pulkoski-Gross
- Department of Pharmacological Sciences, Stony Brook University, Stony Brook, NY 11790.,Department of Medicine and Stony Brook Cancer Center, Stony Brook University, Stony Brook, NY 11790
| | - Meredith L Jenkins
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia V8N 1A1, Canada
| | - Jean-Philip Truman
- Department of Medicine and Stony Brook Cancer Center, Stony Brook University, Stony Brook, NY 11790
| | - Mohamed F Salama
- Department of Biochemistry, Faculty of Veterinary Medicine, Mansoura University, Mansoura 35511, Egypt
| | - Christopher J Clarke
- Department of Medicine and Stony Brook Cancer Center, Stony Brook University, Stony Brook, NY 11790
| | - John E Burke
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia V8N 1A1, Canada
| | - Yusuf A Hannun
- Department of Medicine and Stony Brook Cancer Center, Stony Brook University, Stony Brook, NY 11790
| | - Lina M Obeid
- Department of Medicine and Stony Brook Cancer Center, Stony Brook University, Stony Brook, NY 11790 .,Northport Veterans Affairs Medical Center, Northport, NY 11768
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62
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Moruno Manchon JF, Uzor NE, Finkbeiner S, Tsvetkov AS. SPHK1/sphingosine kinase 1-mediated autophagy differs between neurons and SH-SY5Y neuroblastoma cells. Autophagy 2018; 12:1418-24. [PMID: 27467777 DOI: 10.1080/15548627.2016.1183082] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Although implicated in neurodegeneration, autophagy has been characterized mostly in yeast and mammalian non-neuronal cells. In a recent study, we sought to determine if SPHK1 (sphingosine kinase 1), implicated previously in macroautophagy/autophagy in cancer cells, regulates autophagy in neurons. SPHK1 synthesizes sphingosine-1-phosphate (S1P), a bioactive lipid involved in cell survival. In our study, we discovered that, when neuronal autophagy is pharmacologically stimulated, SPHK1 relocalizes to the endocytic and autophagic organelles. Interestingly, in non-neuronal cells stimulated with growth factors, SPHK1 translocates to the plasma membrane, where it phosphorylates sphingosine to produce S1P. Whether SPHK1 also binds to the endocytic and autophagic organelles in non-neuronal cells upon induction of autophagy has not been demonstrated. Here, we determined if the effect in neurons is operant in the SH-SY5Y neuroblastoma cell line. In both non-differentiated and differentiated SH-SY5Y cells, a short incubation of cells in amino acid-free medium stimulated the formation of SPHK1-positive puncta, as in neurons. We also found that, unlike neurons in which these puncta represent endosomes, autophagosomes, and amphisomes, in SH-SY5Y cells SPHK1 is bound only to the endosomes. In addition, a dominant negative form of SPHK1 was very toxic to SH-SY5Y cells, but cultured primary cortical neurons tolerated it significantly better. These results suggest that autophagy in neurons is regulated by mechanisms that differ, at least in part, from those in SH-SY5Y cells.
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Affiliation(s)
- Jose Felix Moruno Manchon
- a Department of Neurobiology and Anatomy , the University of Texas McGovern Medical School , Houston , TX , USA
| | - Ndidi-Ese Uzor
- a Department of Neurobiology and Anatomy , the University of Texas McGovern Medical School , Houston , TX , USA.,b University of Texas Graduate School of Biomedical Sciences , Houston , TX , USA
| | - Steven Finkbeiner
- c Gladstone Institute of Neurological Disease and the Taube/Koret Center for Neurodegenerative Disease Research , San Francisco , CA , USA.,d Departments of Neurology and Physiology , University of California , San Francisco , CA , USA
| | - Andrey S Tsvetkov
- a Department of Neurobiology and Anatomy , the University of Texas McGovern Medical School , Houston , TX , USA.,b University of Texas Graduate School of Biomedical Sciences , Houston , TX , USA
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63
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Sphingosine Kinase 1 Cooperates with Autophagy to Maintain Endocytic Membrane Trafficking. Cell Rep 2017; 17:1532-1545. [PMID: 27806293 DOI: 10.1016/j.celrep.2016.10.019] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Revised: 09/15/2016] [Accepted: 10/05/2016] [Indexed: 11/21/2022] Open
Abstract
Sphingosine kinase 1 (Sphk1) associates with early endocytic membranes during endocytosis; however, the role of sphingosine or sphingosine-1-phosphate as the critical metabolite in endocytic trafficking has not been established. Here, we demonstrate that the recruitment of Sphk1 to sphingosine-enriched endocytic vesicles and the generation of sphingosine-1-phosphate facilitate membrane trafficking along the endosomal pathway. Exogenous sphingosine and sphingosine-based Sphk1 inhibitors induce the Sphk1-dependent fusion of endosomal membranes to accumulate enlarged late endosomes and amphisomes enriched in sphingolipids. Interestingly, Sphk1 also appears to facilitate endosomal fusion independent of its catalytic activity, given that catalytically inactive Sphk1G82D is recruited to endocytic membranes by sphingosine or sphingosine-based Sphk1 inhibitor and promotes membrane fusion. Furthermore, we reveal that the clearance of enlarged endosomes is dependent on the activity of ceramide synthase, lysosomal biogenesis, and the restoration of autophagic flux. Collectively, these studies uncover intersecting roles for Sphk1, sphingosine, and autophagic machinery in endocytic membrane trafficking.
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64
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Hirama T, Lu SM, Kay JG, Maekawa M, Kozlov MM, Grinstein S, Fairn GD. Membrane curvature induced by proximity of anionic phospholipids can initiate endocytosis. Nat Commun 2017; 8:1393. [PMID: 29123120 PMCID: PMC5680216 DOI: 10.1038/s41467-017-01554-9] [Citation(s) in RCA: 74] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2016] [Accepted: 09/27/2017] [Indexed: 11/09/2022] Open
Abstract
The plasma membrane is uniquely enriched in phosphatidylserine (PtdSer). This anionic phospholipid is restricted almost exclusively to the inner leaflet of the plasmalemma. Because of their high density, the headgroups of anionic lipids experience electrostatic repulsion that, being exerted asymmetrically, is predicted to favor membrane curvature. We demonstrate that cholesterol limits this repulsion and tendency to curve. Removal of cholesterol or insertion of excess PtdSer increases the charge density of the inner leaflet, generating foci of enhanced charge and curvature where endophilin and synaptojanin are recruited. From these sites emerge tubules that undergo fragmentation, resulting in marked endocytosis of PtdSer. Shielding or reduction of the surface charge or imposition of outward membrane tension minimized invagination and PtdSer endocytosis. We propose that cholesterol associates with PtdSer to form nanodomains where the headgroups of PtdSer are maintained sufficiently separated to limit spontaneous curvature while sheltering the hydrophobic sterol from the aqueous medium.
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Affiliation(s)
- Takashi Hirama
- Program in Cell Biology, The Hospital for Sick Children, 555 University Avenue, Toronto, ON, Canada, M5G 1X8.,Department of Respiratory Medicine, Saitama Medical University, Moroyama, Saitama, 3500495, Japan.,Keenan Research Centre for Biomedical Science, St. Michael's Hospital, 209 Victoria Street, Toronto, ON, Canada, M5B 1T8
| | - Stella M Lu
- Program in Cell Biology, The Hospital for Sick Children, 555 University Avenue, Toronto, ON, Canada, M5G 1X8.,Keenan Research Centre for Biomedical Science, St. Michael's Hospital, 209 Victoria Street, Toronto, ON, Canada, M5B 1T8.,Department of Biochemistry, University of Toronto, Toronto, ON, Canada, M5S 1A8
| | - Jason G Kay
- Department of Oral Biology, School of Dental Medicine, University at Buffalo, Buffalo, NY, 14214, USA
| | - Masashi Maekawa
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, 209 Victoria Street, Toronto, ON, Canada, M5B 1T8.,Department of Biochemistry and Molecular Genetics, Ehime University Graduate School of Medicine; Division of Cell Growth and Tumour Regulation, Proteo-Science Center, Ehime University, Toon, Ehime, 7910295, Japan
| | - Michael M Kozlov
- Department of Physiology and Pharmacology, Room 546, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Sergio Grinstein
- Program in Cell Biology, The Hospital for Sick Children, 555 University Avenue, Toronto, ON, Canada, M5G 1X8.,Department of Biochemistry, University of Toronto, Toronto, ON, Canada, M5S 1A8.,Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, ON, Canada, M5S 1A8
| | - Gregory D Fairn
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, 209 Victoria Street, Toronto, ON, Canada, M5B 1T8. .,Department of Biochemistry, University of Toronto, Toronto, ON, Canada, M5S 1A8. .,Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, ON, Canada, M5S 1A8. .,Department of Surgery, University of Toronto, Toronto, ON, Canada, M5T 1P5.
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65
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Chan JP, Brown J, Hark B, Nolan A, Servello D, Hrobuchak H, Staab TA. Loss of Sphingosine Kinase Alters Life History Traits and Locomotor Function in Caenorhabditis elegans. Front Genet 2017; 8:132. [PMID: 28983319 PMCID: PMC5613162 DOI: 10.3389/fgene.2017.00132] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2017] [Accepted: 09/06/2017] [Indexed: 12/15/2022] Open
Abstract
Sphingolipid metabolism is important to balance the abundance of bioactive lipid molecules involved in cell signaling, neuronal function, and survival. Specifically, the sphingolipid sphingosine mediates cell death signaling, whereas its phosphorylated form, sphingosine-1-phosphate (S1P), mediates cell survival signaling. The enzyme sphingosine kinase produces S1P, and the activity of sphingosine kinase impacts the ability of cells to survive under stress and challenges. To examine the influence of sphingolipid metabolism, particularly enzymes regulating sphingosine and S1P, in mediating aging, neuronal function and stress response, we examined life history traits, locomotor capacities and heat stress responses of young and old animals using the model organism Caenorhabditis elegans. We found that C. elegans sphk-1 mutants, which lack sphingosine kinase, had shorter lifespans, reduced brood sizes, and smaller body sizes compared to wild type animals. By analyzing a panel of young and old animals with genetic mutations in the sphingolipid signaling pathway, we showed that aged sphk-1 mutants exhibited a greater decline in neuromuscular function and locomotor behavior. In addition, aged animals lacking sphk-1 were more susceptible to death induced by acute and prolonged heat exposure. On the other hand, older animals with loss of function mutations in ceramide synthase (hyl-1), which converts sphingosine to ceramide, showed improved neuromuscular function and stress response with age. This phenotype was dependent on sphk-1. Together, our data show that loss of sphingosine kinase contributes to poor animal health span, suggesting that sphingolipid signaling may be important for healthy neuronal function and animal stress response during aging.
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Affiliation(s)
- Jason P Chan
- Department of Biology, Juniata CollegeHuntingdon, PA, United States
| | - Jaylene Brown
- Department of Biology, Juniata CollegeHuntingdon, PA, United States
| | - Brandon Hark
- Department of Biology, Juniata CollegeHuntingdon, PA, United States
| | - Abby Nolan
- Department of Biology, Juniata CollegeHuntingdon, PA, United States
| | - Dustin Servello
- Department of Biology, Juniata CollegeHuntingdon, PA, United States
| | - Hannah Hrobuchak
- Department of Biology, Juniata CollegeHuntingdon, PA, United States
| | - Trisha A Staab
- Department of Biology, Juniata CollegeHuntingdon, PA, United States
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66
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Pyne NJ, El Buri A, Adams DR, Pyne S. Sphingosine 1-phosphate and cancer. Adv Biol Regul 2017; 68:97-106. [PMID: 28942351 DOI: 10.1016/j.jbior.2017.09.006] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Revised: 09/13/2017] [Accepted: 09/13/2017] [Indexed: 01/08/2023]
Abstract
The bioactive lipid, sphingosine 1-phosphate (S1P) is produced by phosphorylation of sphingosine and this is catalysed by two sphingosine kinase isoforms (SK1 and SK2). Here we discuss structural functional aspects of SK1 (which is a dimeric quaternary enzyme) that relate to coordinated coupling of membrane association with phosphorylation of Ser225 in the 'so-called' R-loop, catalytic activity and protein-protein interactions (e.g. TRAF2, PP2A and Gq). S1P formed by SK1 at the plasma-membrane is released from cells via S1P transporters to act on S1P receptors to promote tumorigenesis. We discuss here an additional novel mechanism that can operate between cancer cells and fibroblasts and which involves the release of the S1P receptor, S1P2 in exosomes from breast cancer cells that regulates ERK-1/2 signalling in fibroblasts. This novel mechanism of signalling might provide an explanation for the role of S1P2 in promoting metastasis of cancer cells and which is dependent on the micro-environmental niche.
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Affiliation(s)
- Nigel J Pyne
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral St, Glasgow, G4 0RE, Scotland, UK.
| | - Ashref El Buri
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral St, Glasgow, G4 0RE, Scotland, UK
| | - David R Adams
- Institute of Chemical Sciences, Heriot-Watt University, Edinburgh, EH14 4AS, Scotland, UK
| | - Susan Pyne
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral St, Glasgow, G4 0RE, Scotland, UK
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67
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Ma S, Santhosh D, Kumar T P, Huang Z. A Brain-Region-Specific Neural Pathway Regulating Germinal Matrix Angiogenesis. Dev Cell 2017; 41:366-381.e4. [PMID: 28535372 DOI: 10.1016/j.devcel.2017.04.014] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Revised: 02/28/2017] [Accepted: 04/20/2017] [Indexed: 01/05/2023]
Abstract
Intimate communication between neural and vascular cells is critical for normal brain development and function. Germinal matrix (GM), a key primordium for the brain reward circuitry, is unique among brain regions for its distinct pace of angiogenesis and selective vulnerability to hemorrhage during development. A major neonatal condition, GM hemorrhage can lead to cerebral palsy, hydrocephalus, and mental retardation. Here we identify a brain-region-specific neural progenitor-based signaling pathway dedicated to regulating GM vessel development. This pathway consists of cell-surface sphingosine-1-phosphate receptors, an intracellular cascade including Gα co-factor Ric8a and p38 MAPK, and target gene integrin β8, which in turn regulates vascular TGF-β signaling. These findings provide insights into region-specific specialization of neurovascular communication, with special implications for deciphering potent early-life endocrine, as well as potential gut microbiota impacts on brain reward circuitry. They also identify tissue-specific molecular targets for GM hemorrhage intervention.
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Affiliation(s)
- Shang Ma
- Departments of Neuroscience and Neurology, University of Wisconsin-Madison, Madison, WI, 53705, USA; Program in Cellular and Molecular Biology, University of Wisconsin-Madison, Madison, WI53706, USA
| | - Devi Santhosh
- Departments of Neuroscience and Neurology, University of Wisconsin-Madison, Madison, WI, 53705, USA; Program in Genetics and Medical Genetics, University of Wisconsin-Madison, Madison, WI53706, USA
| | - Peeyush Kumar T
- Departments of Neuroscience and Neurology, University of Wisconsin-Madison, Madison, WI, 53705, USA
| | - Zhen Huang
- Departments of Neuroscience and Neurology, University of Wisconsin-Madison, Madison, WI, 53705, USA; Program in Cellular and Molecular Biology, University of Wisconsin-Madison, Madison, WI53706, USA; Program in Genetics and Medical Genetics, University of Wisconsin-Madison, Madison, WI53706, USA.
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68
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Yue HY, Bieberich E, Xu J. Promotion of endocytosis efficiency through an ATP-independent mechanism at rat calyx of Held terminals. J Physiol 2017; 595:5265-5284. [PMID: 28555839 DOI: 10.1113/jp274275] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2017] [Accepted: 05/15/2017] [Indexed: 01/14/2023] Open
Abstract
KEY POINTS At rat calyx of Held terminals, ATP was required not only for slow endocytosis, but also for rapid phase of compensatory endocytosis. An ATP-independent form of endocytosis was recruited to accelerate membrane retrieval at increased activity and temperature. ATP-independent endocytosis primarily involved retrieval of pre-existing membrane, which depended on Ca2+ and the activity of neutral sphingomyelinase but not clathrin-coated pit maturation. ATP-independent endocytosis represents a non-canonical mechanism that can efficiently retrieve membrane at physiological conditions without competing for the limited ATP at elevated neuronal activity. ABSTRACT Neurotransmission relies on membrane endocytosis to maintain vesicle supply and membrane stability. Endocytosis has been generally recognized as a major ATP-dependent function, which efficiently retrieves more membrane at elevated neuronal activity when ATP consumption within nerve terminals increases drastically. This paradox raises the interesting question of whether increased activity recruits ATP-independent mechanism(s) to accelerate endocytosis at the same time as preserving ATP availability for other tasks. To address this issue, we studied ATP requirement in three typical forms of endocytosis at rat calyx of Held terminals by whole-cell membrane capacitance measurements. At room temperature, blocking ATP hydrolysis effectively abolished slow endocytosis and rapid endocytosis but only partially inhibited excess endocytosis following intense stimulation. The ATP-independent endocytosis occurred at calyces from postnatal days 8-15, suggesting its existence before and after hearing onset. This endocytosis was not affected by a reduction of exocytosis using the light chain of botulinum toxin C, nor by block of clathrin-coat maturation. It was abolished by EGTA, which preferentially blocked endocytosis of retrievable membrane pre-existing at the surface, and was impaired by oxidation of cholesterol and inhibition of neutral sphingomyelinase. ATP-independent endocytosis became more significant at 34-35°C, and recovered membrane by an amount that, on average, was close to exocytosis. The results of the present study suggest that activity and temperature recruit ATP-independent endocytosis of pre-existing membrane (in addition to ATP-dependent endocytosis) to efficiently retrieve membrane at nerve terminals. This less understood endocytosis represents a non-canonical mechanism regulated by lipids such as cholesterol and sphingomyelinase.
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Affiliation(s)
- Hai-Yuan Yue
- Departments of Neuroscience and Regenerative Medicine, Augusta University, USA
| | - Erhard Bieberich
- Departments of Neuroscience and Regenerative Medicine, Augusta University, USA
| | - Jianhua Xu
- Departments of Neuroscience and Regenerative Medicine, Augusta University, USA.,Department of Neurology, Medical College of Georgia, Augusta University, USA
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69
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McCulloch KA, Qi YB, Takayanagi-Kiya S, Jin Y, Cherra SJ. Novel Mutations in Synaptic Transmission Genes Suppress Neuronal Hyperexcitation in Caenorhabditis elegans. G3 (BETHESDA, MD.) 2017; 7:2055-2063. [PMID: 28468816 PMCID: PMC5499116 DOI: 10.1534/g3.117.042598] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Accepted: 04/22/2017] [Indexed: 01/29/2023]
Abstract
Acetylcholine (ACh) receptors (AChR) regulate neural circuit activity in multiple contexts. In humans, mutations in ionotropic acetylcholine receptor (iAChR) genes can cause neurological disorders, including myasthenia gravis and epilepsy. In Caenorhabditis elegans, iAChRs play multiple roles in the locomotor circuit. The cholinergic motor neurons express an ACR-2-containing pentameric AChR (ACR-2R) comprised of ACR-2, ACR-3, ACR-12, UNC-38, and UNC-63 subunits. A gain-of-function mutation in the non-α subunit gene acr-2 [acr-2(gf)] causes defective locomotion as well as spontaneous convulsions. Previous studies of genetic suppressors of acr-2(gf) have provided insights into ACR-2R composition and assembly. Here, to further understand how the ACR-2R regulates neuronal activity, we expanded the suppressor screen for acr-2(gf)-induced convulsions. The majority of these suppressor mutations affect genes that play critical roles in synaptic transmission, including two novel mutations in the vesicular ACh transporter unc-17 In addition, we identified a role for a conserved major facilitator superfamily domain (MFSD) protein, mfsd-6, in regulating neural circuit activity. We further defined a role for the sphingosine (SPH) kinase (Sphk) sphk-1 in cholinergic neuron activity, independent of previously known signaling pathways. Overall, the genes identified in our study suggest that optimal modulation of synaptic activity is balanced by the differential activities of multiple pathways, and the novel alleles provide valuable reagents to further dissect neuronal mechanisms regulating the locomotor circuit.
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Affiliation(s)
- Katherine A McCulloch
- Section of Neurobiology, Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093
| | - Yingchuan B Qi
- Section of Neurobiology, Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093
| | - Seika Takayanagi-Kiya
- Section of Neurobiology, Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093
| | - Yishi Jin
- Section of Neurobiology, Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, California 92093
- Howard Hughes Medical Institute, University of California, San Diego, La Jolla, California 92093
| | - Salvatore J Cherra
- Section of Neurobiology, Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093
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70
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Hatoum D, Haddadi N, Lin Y, Nassif NT, McGowan EM. Mammalian sphingosine kinase (SphK) isoenzymes and isoform expression: challenges for SphK as an oncotarget. Oncotarget 2017; 8:36898-36929. [PMID: 28415564 PMCID: PMC5482707 DOI: 10.18632/oncotarget.16370] [Citation(s) in RCA: 77] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Accepted: 03/02/2017] [Indexed: 12/16/2022] Open
Abstract
The various sphingosine kinase (SphK) isoenzymes (isozymes) and isoforms, key players in normal cellular physiology, are strongly implicated in cancer and other diseases. Mutations in SphKs, that may justify abnormal physiological function, have not been recorded. Nonetheless, there is a large and growing body of evidence demonstrating the contribution of gain or loss of function and the imbalance in the SphK/S1P rheostat to a plethora of pathological conditions including cancer, diabetes and inflammatory diseases. SphK is expressed as two isozymes SphK1 and SphK2, transcribed from genes located on different chromosomes and both isozymes catalyze the phosphorylation of sphingosine to S1P. Expression of each SphK isozyme produces alternately spliced isoforms. In recent years the importance of the contribution of SpK1 expression to treatment resistance in cancer has been highlighted and, additionally, differences in treatment outcome appear to also be dependent upon SphK isoform expression. This review focuses on an exciting emerging area of research involving SphKs functions, expression and subcellular localization, highlighting the complexity of targeting SphK in cancer and also comorbid diseases. This review also covers the SphK isoenzymes and isoforms from a historical perspective, from their first discovery in murine species and then in humans, their role(s) in normal cellular function and in disease processes, to advancement of SphK as an oncotarget.
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Affiliation(s)
- Diana Hatoum
- School of Life Sciences, University of Technology Sydney, Ultimo, Sydney, NSW 2007, Australia
| | - Nahal Haddadi
- School of Life Sciences, University of Technology Sydney, Ultimo, Sydney, NSW 2007, Australia
| | - Yiguang Lin
- School of Life Sciences, University of Technology Sydney, Ultimo, Sydney, NSW 2007, Australia
| | - Najah T. Nassif
- School of Life Sciences, University of Technology Sydney, Ultimo, Sydney, NSW 2007, Australia
| | - Eileen M. McGowan
- School of Life Sciences, University of Technology Sydney, Ultimo, Sydney, NSW 2007, Australia
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71
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Garcia‐Gil M, Pierucci F, Vestri A, Meacci E. Crosstalk between sphingolipids and vitamin D3: potential role in the nervous system. Br J Pharmacol 2017; 174:605-627. [PMID: 28127747 PMCID: PMC6398521 DOI: 10.1111/bph.13726] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Revised: 12/16/2016] [Accepted: 01/18/2017] [Indexed: 12/14/2022] Open
Abstract
Sphingolipids are both structural and bioactive compounds. In particular, ceramide and sphingosine 1-phosphate regulate cell fate, inflammation and excitability. 1-α,25-dihydroxyvitamin D3 (1,25(OH)2 D3 ) is known to play an important physiological role in growth and differentiation in a variety of cell types, including neural cells, through genomic actions mediated by its specific receptor, and non-genomic effects that result in the activation of specific signalling pathways. 1,25(OH)2 D3 and sphingolipids, in particular sphingosine 1-phosphate, share many common effectors, including calcium regulation, growth factors and inflammatory cytokines, but it is still not known whether they can act synergistically. Alterations in the signalling and concentrations of sphingolipids and 1,25(OH)2 D3 have been found in neurodegenerative diseases and fingolimod, a structural analogue of sphingosine, has been approved for the treatment of multiple sclerosis. This review, after a brief description of the role of sphingolipids and 1,25(OH)2 D3 , will focus on the potential crosstalk between sphingolipids and 1,25(OH)2 D3 in neural cells.
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Affiliation(s)
- Mercedes Garcia‐Gil
- Department of BiologyUniversity of PisaPisaItaly
- Interdepartmental Research Center Nutrafood ‘Nutraceuticals and Food for Health’University of PisaPisaItaly
| | - Federica Pierucci
- Department of Experimental and Clinical Biomedical Sciences ‘Mario Serio’, Molecular and Applied Biology Research UnitUniversity of FlorenceFlorenceItaly
- Interuniversitary Miology InstitutesItaly
| | - Ambra Vestri
- Department of Experimental and Clinical Biomedical Sciences ‘Mario Serio’, Molecular and Applied Biology Research UnitUniversity of FlorenceFlorenceItaly
- Interuniversitary Miology InstitutesItaly
| | - Elisabetta Meacci
- Department of Experimental and Clinical Biomedical Sciences ‘Mario Serio’, Molecular and Applied Biology Research UnitUniversity of FlorenceFlorenceItaly
- Interuniversitary Miology InstitutesItaly
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72
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Kinoshita M, Suzuki KGN, Matsumori N, Takada M, Ano H, Morigaki K, Abe M, Makino A, Kobayashi T, Hirosawa KM, Fujiwara TK, Kusumi A, Murata M. Raft-based sphingomyelin interactions revealed by new fluorescent sphingomyelin analogs. J Cell Biol 2017; 216:1183-1204. [PMID: 28330937 PMCID: PMC5379944 DOI: 10.1083/jcb.201607086] [Citation(s) in RCA: 94] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 12/30/2016] [Accepted: 02/02/2017] [Indexed: 01/01/2023] Open
Abstract
Sphingomyelin (SM) has been proposed to form cholesterol-dependent raft domains and sphingolipid domains in the plasma membrane (PM). How SM contributes to the formation and function of these domains remains unknown, primarily because of the scarcity of suitable fluorescent SM analogs. We developed new fluorescent SM analogs by conjugating a hydrophilic fluorophore to the SM choline headgroup without eliminating its positive charge, via a hydrophilic nonaethylene glycol linker. The new analogs behaved similarly to the native SM in terms of their partitioning behaviors in artificial liquid order-disorder phase-separated membranes and detergent-resistant PM preparations. Single fluorescent molecule tracking in the live-cell PM revealed that they indirectly interact with each other in cholesterol- and sphingosine backbone-dependent manners, and that, for ∼10-50 ms, they undergo transient colocalization-codiffusion with a glycosylphosphatidylinositol (GPI)-anchored protein, CD59 (in monomers, transient-dimer rafts, and clusters), in CD59-oligomer size-, cholesterol-, and GPI anchoring-dependent manners. These results suggest that SM continually and rapidly exchanges between CD59-associated raft domains and the bulk PM.
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Affiliation(s)
- Masanao Kinoshita
- Lipid Active Structure Project, Exploratory Research for Advanced Technology Organization, Japan Science and Technology Agency, Osaka University, Osaka 560-0043, Japan.,Project Research Center for Fundamental Science, Osaka University, Osaka 560-0043, Japan
| | - Kenichi G N Suzuki
- Institute for Integrated Cell-Material Sciences, Kyoto University, Kyoto 606-8507, Japan.,The Institute for Stem Cell Biology and Regenerative Medicine, The National Centre for Biological Sciences, Bangalore 560065, India
| | - Nobuaki Matsumori
- Lipid Active Structure Project, Exploratory Research for Advanced Technology Organization, Japan Science and Technology Agency, Osaka University, Osaka 560-0043, Japan .,Project Research Center for Fundamental Science, Osaka University, Osaka 560-0043, Japan.,Department of Chemistry, Graduate School of Science, Osaka University, Osaka 560-0043, Japan
| | - Misa Takada
- Department of Chemistry, Graduate School of Science, Osaka University, Osaka 560-0043, Japan
| | - Hikaru Ano
- Lipid Active Structure Project, Exploratory Research for Advanced Technology Organization, Japan Science and Technology Agency, Osaka University, Osaka 560-0043, Japan.,Project Research Center for Fundamental Science, Osaka University, Osaka 560-0043, Japan
| | - Kenichi Morigaki
- Research Center for Environmental Genomics, Kobe University, Kobe 657-8501, Japan
| | - Mitsuhiro Abe
- Cellular Informatics Laboratory, Institute of Physical and Chemical Research, Wako, Saitama 351-0198, Japan
| | - Asami Makino
- Cellular Informatics Laboratory, Institute of Physical and Chemical Research, Wako, Saitama 351-0198, Japan
| | - Toshihide Kobayashi
- UMR 7213 Centre National de la Recherche Scientifique, University of Strasbourg, Illkirch 67401, France
| | - Koichiro M Hirosawa
- Institute for Integrated Cell-Material Sciences, Kyoto University, Kyoto 606-8507, Japan
| | - Takahiro K Fujiwara
- Institute for Integrated Cell-Material Sciences, Kyoto University, Kyoto 606-8507, Japan
| | - Akihiro Kusumi
- Institute for Integrated Cell-Material Sciences, Kyoto University, Kyoto 606-8507, Japan .,Institute for Frontier Medical Sciences, Kyoto University, Kyoto 606-8507, Japan.,Membrane Cooperativity Unit, Okinawa Institute of Science and Technology, Okinawa 904-0412, Japan
| | - Michio Murata
- Lipid Active Structure Project, Exploratory Research for Advanced Technology Organization, Japan Science and Technology Agency, Osaka University, Osaka 560-0043, Japan.,Project Research Center for Fundamental Science, Osaka University, Osaka 560-0043, Japan.,Department of Chemistry, Graduate School of Science, Osaka University, Osaka 560-0043, Japan
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73
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Ailte I, Lingelem ABD, Kvalvaag AS, Kavaliauskiene S, Brech A, Koster G, Dommersnes PG, Bergan J, Skotland T, Sandvig K. Exogenous lysophospholipids with large head groups perturb clathrin-mediated endocytosis. Traffic 2017; 18:176-191. [PMID: 28067430 DOI: 10.1111/tra.12468] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Revised: 01/03/2017] [Accepted: 01/04/2017] [Indexed: 12/12/2022]
Abstract
In this study, we have investigated how clathrin-dependent endocytosis is affected by exogenously added lysophospholipids (LPLs). Addition of LPLs with large head groups strongly inhibits transferrin (Tf) endocytosis in various cell lines, while LPLs with small head groups do not. Electron and total internal reflection fluorescence microscopy (EM and TIRF) reveal that treatment with lysophosphatidylinositol (LPI) with the fatty acyl group C18:0 leads to reduced numbers of invaginated clathrin-coated pits (CCPs) at the plasma membrane, fewer endocytic events per membrane area and increased lifetime of CCPs. Also, endocytosis of Tf becomes dependent on actin upon LPI treatment. Thus, our results demonstrate that one can regulate the kinetics and properties of clathrin-dependent endocytosis by addition of LPLs in a head group size- and fatty acyl-dependent manner. Furthermore, studies performed with optical tweezers show that less force is required to pull membrane tubules outwards from the plasma membrane when LPI is added to the cells. The results are in agreement with the notion that insertion of LPLs with large head groups creates a positive membrane curvature which might have a negative impact on events that require plasma membrane invagination, while it may facilitate membrane bending toward the cell exterior.
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Affiliation(s)
- Ieva Ailte
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Oslo, Norway.,Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway.,Department of Biosciences, University of Oslo, Oslo, Norway
| | - Anne Berit D Lingelem
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Oslo, Norway.,Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway
| | - Audun S Kvalvaag
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Oslo, Norway.,Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway
| | - Simona Kavaliauskiene
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Oslo, Norway.,Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway.,Department of Biosciences, University of Oslo, Oslo, Norway
| | - Andreas Brech
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Oslo, Norway.,Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway.,Department of Biosciences, University of Oslo, Oslo, Norway
| | | | - Paul G Dommersnes
- Department of Physics, Norwegian University of Science and Technology, Trondheim, Norway
| | - Jonas Bergan
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Oslo, Norway.,Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway
| | - Tore Skotland
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Oslo, Norway.,Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway
| | - Kirsten Sandvig
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Oslo, Norway.,Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway.,Department of Biosciences, University of Oslo, Oslo, Norway
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74
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Lima S, Milstien S, Spiegel S. Sphingosine and Sphingosine Kinase 1 Involvement in Endocytic Membrane Trafficking. J Biol Chem 2017; 292:3074-3088. [PMID: 28049734 DOI: 10.1074/jbc.m116.762377] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Revised: 12/22/2016] [Indexed: 12/22/2022] Open
Abstract
The balance between cholesterol and sphingolipids within the plasma membrane has long been implicated in endocytic membrane trafficking. However, in contrast to cholesterol functions, little is still known about the roles of sphingolipids and their metabolites. Perturbing the cholesterol/sphingomyelin balance was shown to induce narrow tubular plasma membrane invaginations enriched with sphingosine kinase 1 (SphK1), the enzyme that converts the bioactive sphingolipid metabolite sphingosine to sphingosine-1-phosphate, and suggested a role for sphingosine phosphorylation in endocytic membrane trafficking. Here we show that sphingosine and sphingosine-like SphK1 inhibitors induced rapid and massive formation of vesicles in diverse cell types that accumulated as dilated late endosomes. However, much smaller vesicles were formed in SphK1-deficient cells. Moreover, inhibition or deletion of SphK1 prolonged the lifetime of sphingosine-induced vesicles. Perturbing the plasma membrane cholesterol/sphingomyelin balance abrogated vesicle formation. This massive endosomal influx was accompanied by dramatic recruitment of the intracellular SphK1 and Bin/Amphiphysin/Rvs domain-containing proteins endophilin-A2 and endophilin-B1 to enlarged endosomes and formation of highly dynamic filamentous networks containing endophilin-B1 and SphK1. Together, our results highlight the importance of sphingosine and its conversion to sphingosine-1-phosphate by SphK1 in endocytic membrane trafficking.
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Affiliation(s)
- Santiago Lima
- Department of Biochemistry and Molecular Biology and Massey Cancer Center, Virginia Commonwealth University School of Medicine, Richmond, Virginia 23298.
| | - Sheldon Milstien
- Department of Biochemistry and Molecular Biology and Massey Cancer Center, Virginia Commonwealth University School of Medicine, Richmond, Virginia 23298
| | - Sarah Spiegel
- Department of Biochemistry and Molecular Biology and Massey Cancer Center, Virginia Commonwealth University School of Medicine, Richmond, Virginia 23298.
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75
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Raben DM, Barber CN. Phosphatidic acid and neurotransmission. Adv Biol Regul 2016; 63:15-21. [PMID: 27671966 DOI: 10.1016/j.jbior.2016.09.004] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 09/15/2016] [Accepted: 09/19/2016] [Indexed: 12/31/2022]
Abstract
Lipids play a vital role in the health and functioning of neurons and interest in the physiological role of neuronal lipids is certainly increasing. One neuronal function in which neuronal lipids appears to play key roles in neurotransmission. Our understanding of the role of lipids in the synaptic vesicle cycle and neurotransmitter release is becoming increasingly more important. Much of the initial research in this area has highlighted the major roles played by the phosphoinositides (PtdIns), diacylglycerol (DAG), and phosphatidic acid (PtdOH). Of these, PtdOH has not received as much attention as the other lipids although its role and metabolism appears to be extremely important. This lipid has been shown to play a role in modulating both exocytosis and endocytosis although its precise role in either process is not well defined. The currently evidence suggest this lipid likely participates in key processes by altering membrane architecture necessary for membrane fusion, mediating the penetration of membrane proteins, serving as a precursor for other important SV cycling lipids, or activating essential enzymes. In this review, we address the sources of PtdOH, the enzymes involved in its production, the regulation of these enzymes, and its potential roles in neurotransmission in the central nervous system.
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Affiliation(s)
- Daniel M Raben
- The Department of Biological Chemistry, The Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA.
| | - Casey N Barber
- The Department of Biological Chemistry, The Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA
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76
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Sphingosine Kinases: Emerging Structure-Function Insights. Trends Biochem Sci 2016; 41:395-409. [PMID: 27021309 DOI: 10.1016/j.tibs.2016.02.007] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Revised: 02/08/2016] [Accepted: 02/17/2016] [Indexed: 12/15/2022]
Abstract
Sphingosine kinases (SK1 and SK2) catalyse the conversion of sphingosine into sphingosine 1-phosphate and control fundamental cellular processes, including cell survival, proliferation, differentiation, migration, and immune function. In this review, we highlight recent breakthroughs in the structural and functional characterisation of SK1 and these are contextualised by analysis of crystal structures for closely related prokaryotic lipid kinases. We identify a putative dimerisation interface and propose novel regulatory mechanisms governing structural plasticity induced by phosphorylation and interaction with phospholipids and proteins. Our analysis suggests that the catalytic function and regulation of the enzymes might be dependent on conformational mobility and it provides a roadmap for future interrogation of SK1 function and its role in physiology and disease.
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77
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Pyne S, Adams DR, Pyne NJ. Sphingosine 1-phosphate and sphingosine kinases in health and disease: Recent advances. Prog Lipid Res 2016; 62:93-106. [PMID: 26970273 DOI: 10.1016/j.plipres.2016.03.001] [Citation(s) in RCA: 141] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Revised: 03/07/2016] [Accepted: 03/08/2016] [Indexed: 12/24/2022]
Abstract
Sphingosine kinases (isoforms SK1 and SK2) catalyse the formation of a bioactive lipid, sphingosine 1-phosphate (S1P). S1P is a well-established ligand of a family of five S1P-specific G protein coupled receptors but also has intracellular signalling roles. There is substantial evidence to support a role for sphingosine kinases and S1P in health and disease. This review summarises recent advances in the area in relation to receptor-mediated signalling by S1P and novel intracellular targets of this lipid. New evidence for a role of each sphingosine kinase isoform in cancer, the cardiovascular system, central nervous system, inflammation and diabetes is discussed. There is continued research to develop isoform selective SK inhibitors, summarised here. Analysis of the crystal structure of SK1 with the SK1-selective inhibitor, PF-543, is used to identify residues that could be exploited to improve selectivity in SK inhibitor development for future therapeutic application.
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Affiliation(s)
- Susan Pyne
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral St, Glasgow, G4 0RE, Scotland, UK.
| | - David R Adams
- School of Engineering & Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, Scotland, UK.
| | - Nigel J Pyne
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral St, Glasgow, G4 0RE, Scotland, UK.
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78
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Tran HB, Barnawi J, Ween M, Hamon R, Roscioli E, Hodge G, Reynolds PN, Pitson SM, Davies LT, Haberberger R, Hodge S. Cigarette smoke inhibits efferocytosis via deregulation of sphingosine kinase signaling: reversal with exogenous S1P and the S1P analogue FTY720. J Leukoc Biol 2016; 100:195-202. [PMID: 26792820 DOI: 10.1189/jlb.3a1015-471r] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Accepted: 01/04/2016] [Indexed: 12/31/2022] Open
Abstract
Alveolar macrophages from chronic obstructive pulmonary disease patients and cigarette smokers are deficient in their ability to phagocytose apoptotic bronchial epithelial cells (efferocytosis). We hypothesized that the defect is mediated via inhibition of sphingosine kinases and/or their subcellular mislocalization in response to cigarette smoke and can be normalized with exogenous sphingosine-1-phosphate or FTY720 (fingolimod), a modulator of sphingosine-1-phosphate signaling, which has been shown to be clinically useful in multiple sclerosis. Measurement of sphingosine kinase 1/2 activities by [(32)P]-labeled sphingosine-1-phosphate revealed a 30% reduction of sphingosine kinase 1 (P < 0.05) and a nonsignificant decrease of sphingosine kinase 2 in THP-1 macrophages after 1 h cigarette smoke extract exposure. By confocal analysis macrophage sphingosine kinase 1 protein was normally localized to the plasma membrane and cytoplasm and sphingosine kinase 2 to the nucleus and cytoplasm but absent at the cell surface. Cigarette smoke extract exposure (24 h) led to a retraction of sphingosine kinase 1 from the plasma membrane and sphingosine kinase 1/2 clumping in the Golgi domain. Selective inhibition of sphingosine kinase 2 with 25 µM ABC294640 led to 36% inhibition of efferocytosis (P < 0.05); 10 µM sphingosine kinase inhibitor/5C (sphingosine kinase 1-selective inhibitor) induced a nonsignificant inhibition of efferocytosis, but its combination with ABC294640 led to 56% inhibition (P < 0.01 vs. control and < 0.05 vs. single inhibitors). Cigarette smoke-inhibited efferocytosis was significantly (P < 0.05) reversed to near-control levels in the presence of 10-100 nM exogenous sphingosine-1-phosphate or FTY720, and FTY720 reduced cigarette smoke-induced clumping of sphingosine kinase 1/2 in the Golgi domain. These data strongly support a role of sphingosine kinase 1/2 in efferocytosis and as novel therapeutic targets in chronic obstructive pulmonary disease.
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Affiliation(s)
- Hai B Tran
- Lung Research Unit, Hanson Institute and Department of Thoracic Medicine, Royal Adelaide Hospital, Adelaide, Australia;
| | - Jameel Barnawi
- Lung Research Unit, Hanson Institute and Department of Thoracic Medicine, Royal Adelaide Hospital, Adelaide, Australia; Department of Medicine, University of Adelaide, Australia; Department of Medical Laboratory Technology, University of Tabuk, Saudi Arabia
| | - Miranda Ween
- Lung Research Unit, Hanson Institute and Department of Thoracic Medicine, Royal Adelaide Hospital, Adelaide, Australia
| | - Rhys Hamon
- Lung Research Unit, Hanson Institute and Department of Thoracic Medicine, Royal Adelaide Hospital, Adelaide, Australia
| | - Eugene Roscioli
- Lung Research Unit, Hanson Institute and Department of Thoracic Medicine, Royal Adelaide Hospital, Adelaide, Australia
| | - Greg Hodge
- Lung Research Unit, Hanson Institute and Department of Thoracic Medicine, Royal Adelaide Hospital, Adelaide, Australia; Department of Medicine, University of Adelaide, Australia
| | - Paul N Reynolds
- Lung Research Unit, Hanson Institute and Department of Thoracic Medicine, Royal Adelaide Hospital, Adelaide, Australia; Department of Medicine, University of Adelaide, Australia
| | - Stuart M Pitson
- Department of Medicine, University of Adelaide, Australia; Centre for Cancer Biology, University of South Australia and SA Pathology, Adelaide, Australia; and
| | - Lorena T Davies
- Centre for Cancer Biology, University of South Australia and SA Pathology, Adelaide, Australia; and
| | - Rainer Haberberger
- Centre for Neuroscience Anatomy and Histology, Flinders University, Adelaide, Australia
| | - Sandra Hodge
- Lung Research Unit, Hanson Institute and Department of Thoracic Medicine, Royal Adelaide Hospital, Adelaide, Australia; Department of Medicine, University of Adelaide, Australia;
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79
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Methods for Testing Immunological Factors. DRUG DISCOVERY AND EVALUATION: PHARMACOLOGICAL ASSAYS 2016. [PMCID: PMC7122208 DOI: 10.1007/978-3-319-05392-9_45] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Hypersensitivity reactions can be elicited by various factors: either immunologically induced, i.e., allergic reactions to natural or synthetic compounds mediated by IgE, or non-immunologically induced, i.e., activation of mediator release from cells through direct contact, without the induction of, or the mediation through immune responses. Mediators responsible for hypersensitivity reactions are released from mast cells. An important preformed mediator of allergic reactions found in these cells is histamine. Specific allergens or the calcium ionophore 48/80 induce release of histamine from mast cells. The histamine concentration can be determined with the o-phthalaldehyde reaction.
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80
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Abstract
Maintenance of cellular homeostasis requires tight and coordinated control of numerous metabolic pathways, which are governed by interconnected networks of signaling pathways and energy-sensing regulators. Autophagy, a lysosomal degradation pathway by which the cell self-digests its own components, has over the past decade been recognized as an essential part of metabolism. Autophagy not only rids the cell of excessive or damaged organelles, misfolded proteins, and invading microorganisms, it also provides nutrients to maintain crucial cellular functions. Besides serving as essential structural moieties of biomembranes, lipids including sphingolipids are increasingly being recognized as central regulators of a number of important cellular processes, including autophagy. In the present review we describe how sphingolipids, with special emphasis on ceramides and sphingosine-1-phosphate, can act as physiological regulators of autophagy in relation to cellular and organismal growth, survival, and aging.
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Affiliation(s)
- Eva Bang Harvald
- Villum Center for Bioanalytical Sciences, Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark
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Mouse Sphingosine Kinase 1a Is Negatively Regulated through Conventional PKC-Dependent Phosphorylation at S373 Residue. PLoS One 2015; 10:e0143695. [PMID: 26642194 PMCID: PMC4671553 DOI: 10.1371/journal.pone.0143695] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2015] [Accepted: 11/08/2015] [Indexed: 02/02/2023] Open
Abstract
Sphingosine kinase is a lipid kinase that converts sphingosine into sphingosine-1-phosphate, an important signaling molecule with intracellular and extracellular functions. Although diverse extracellular stimuli influence cellular sphingosine kinase activity, the molecular mechanisms underlying its regulation remain to be clarified. In this study, we investigated the phosphorylation-dependent regulation of mouse sphingosine kinase (mSK) isoforms 1 and 2. mSK1a was robustly phosphorylated in response to extracellular stimuli such as phorbol ester, whereas mSK2 exhibited a high basal level of phosphorylation in quiescent cells regardless of agonist stimulation. Interestingly, phorbol ester-induced phosphorylation of mSK1a correlated with suppression of its activity. Chemical inhibition of conventional PKCs (cPKCs) abolished mSK1a phosphorylation, while overexpression of PKCα, a cPKC isoform, potentiated the phosphorylation, in response to phorbol ester. Furthermore, an in vitro kinase assay showed that PKCα directly phosphorylated mSK1a. In addition, phosphopeptide mapping analysis determined that the S373 residue of mSK1a was the only site phosphorylated by cPKC. Interestingly, alanine substitution of S373 made mSK1a refractory to the inhibitory effect of phorbol esters, whereas glutamate substitution of the same residue resulted in a significant reduction in mSK1a activity, suggesting the significant role of this phosphorylation event. Taken together, we propose that mSK1a is negatively regulated through cPKC-dependent phosphorylation at S373 residue.
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82
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Sphingosine Kinase Regulates Microtubule Dynamics and Organelle Positioning Necessary for Proper G1/S Cell Cycle Transition in Trypanosoma brucei. mBio 2015; 6:e01291-15. [PMID: 26443455 PMCID: PMC4611037 DOI: 10.1128/mbio.01291-15] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
UNLABELLED Sphingolipids are important constituents of cell membranes and also serve as mediators of cell signaling and cell recognition. Sphingolipid metabolites such as sphingosine-1-phosphate and ceramide regulate signaling cascades involved in cell proliferation and differentiation, autophagy, inflammation, and apoptosis. Little is known about how sphingolipids and their metabolites function in single-celled eukaryotes. In the present study, we investigated the role of sphingosine kinase (SPHK) in the biology of the protozoan parasite Trypanosoma brucei, the agent of African sleeping sickness. T. brucei SPHK (TbSPHK) is constitutively but differentially expressed during the life cycle of T. brucei. Depletion of TbSPHK in procyclic-form T. brucei causes impaired growth and attenuation in the G1/S phase of the cell cycle. TbSPHK-depleted cells also develop organelle positioning defects and an accumulation of tyrosinated α-tubulin at the elongated posterior end of the cell, known as the "nozzle" phenotype, caused by other molecular perturbations in this organism. Our studies indicate that TbSPHK is involved in G1-to-S cell cycle progression, organelle positioning, and maintenance of cell morphology. Cytotoxicity assays using TbSPHK inhibitors revealed a favorable therapeutic index between T. brucei and human cells, suggesting TbSPHK to be a novel drug target. IMPORTANCE Trypanosoma brucei is a single-celled parasite that is transmitted between humans and other animals by the tsetse fly. T. brucei is endemic in sub-Saharan Africa, where over 70 million people and countless livestock are at risk of developing T. brucei infection, called African sleeping sickness, resulting in economic losses of ~$35 million from the loss of cattle alone. New drugs for this infection are sorely needed and scientists are trying to identify essential enzymes in the parasite that can be targets for new therapies. One possible enzyme target is sphingosine kinase, an enzyme involved in the synthesis of lipids important for cell surface integrity and regulation of cell functions. In this study, we found that sphingosine kinase is essential for normal growth and structure of the parasite, raising the possibility that it could be a good target for new chemotherapy for sleeping sickness.
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83
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Fröhlich F, Petit C, Kory N, Christiano R, Hannibal-Bach HK, Graham M, Liu X, Ejsing CS, Farese RV, Walther TC. The GARP complex is required for cellular sphingolipid homeostasis. eLife 2015; 4. [PMID: 26357016 PMCID: PMC4600884 DOI: 10.7554/elife.08712] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Accepted: 09/09/2015] [Indexed: 12/11/2022] Open
Abstract
Sphingolipids are abundant membrane components and important signaling molecules in eukaryotic cells. Their levels and localization are tightly regulated. However, the mechanisms underlying this regulation remain largely unknown. In this study, we identify the Golgi-associated retrograde protein (GARP) complex, which functions in endosome-to-Golgi retrograde vesicular transport, as a critical player in sphingolipid homeostasis. GARP deficiency leads to accumulation of sphingolipid synthesis intermediates, changes in sterol distribution, and lysosomal dysfunction. A GARP complex mutation analogous to a VPS53 allele causing progressive cerebello-cerebral atrophy type 2 (PCCA2) in humans exhibits similar, albeit weaker, phenotypes in yeast, providing mechanistic insights into disease pathogenesis. Inhibition of the first step of de novo sphingolipid synthesis is sufficient to mitigate many of the phenotypes of GARP-deficient yeast or mammalian cells. Together, these data show that GARP is essential for cellular sphingolipid homeostasis and suggest a therapeutic strategy for the treatment of PCCA2. DOI:http://dx.doi.org/10.7554/eLife.08712.001 Every cell is enveloped by a membrane that forms a barrier between the cell and its environment. This membrane contains fat molecules called ‘sphingolipids’, which help to maintain the structure of the membrane and enable it to work correctly. These molecules are also used as signals to send information around the interior of the cell and are required for the cell to grow and divide normally. The levels of sphingolipids in the membrane have to be tightly controlled because any imbalance can cause stress to the cell and can lead to serious diseases. Sphingolipids are made inside the cell and are then sent to a compartment called the Golgi before being delivered to the membrane. To regulate the amount of sphingolipids in the membrane, these molecules are routinely returned to the interior of the cell in small structures called endosomes. From here, they can either be broken down or recycled back to the membrane via the Golgi. A group of proteins known as the Golgi-associated retrograde protein complex (or GARP) is involved in the movement of endosomes from the membrane to the Golgi. People that have a mutation in the gene that encodes GARP suffer from a severe neurodegenerative disease known as ‘progressive cerebello-cerebral atrophy type 2’ (PCCA2) in which brain cells die prematurely. Researchers have assumed that the most important role of GARP is to sort proteins, and that the missorting of proteins leads to PCCA2. Here, Frohlich et al. used a combination of genetic analysis and biochemical techniques to study GARP in yeast cells. The experiments show that GARP is critical for sphingolipid recycling, and that a lack of GARP leads to more sphingolipids being degraded, which results in a build-up of toxic molecules. Frohlich et al. generated yeast cells that have the same mutations in the gene that encodes GARP as those in human patients with PCCA2. These cells grew much slower than normal yeast and were less able to transport sphingolipids from the endosome to the Golgi. Like the yeast cells, human cells in which the gene that encodes GARP was less active also accumulated toxic molecules. Together, these findings suggest that a build-up of toxic fat molecules may be responsible for the symptoms observed in PCCA2 patients. A future challenge is to find out whether this also applies to patients with Alzheimer's disease and other conditions that also affect endosomes. DOI:http://dx.doi.org/10.7554/eLife.08712.002
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Affiliation(s)
- Florian Fröhlich
- Department of Genetics and Complex Diseases, Harvard T.H. Chan School of Public Health, Boston, United States.,Department of Cell Biology, Harvard Medical School, Boston, United States
| | - Constance Petit
- Department of Genetics and Complex Diseases, Harvard T.H. Chan School of Public Health, Boston, United States.,Department of Cell Biology, Harvard Medical School, Boston, United States
| | - Nora Kory
- Department of Genetics and Complex Diseases, Harvard T.H. Chan School of Public Health, Boston, United States.,Department of Cell Biology, Harvard Medical School, Boston, United States
| | - Romain Christiano
- Department of Genetics and Complex Diseases, Harvard T.H. Chan School of Public Health, Boston, United States.,Department of Cell Biology, Harvard Medical School, Boston, United States
| | - Hans-Kristian Hannibal-Bach
- Department of Biochemistry and Molecular Biology, VILLUM Center for Bioanalytical Sciences, University of Southern Denmark, Odense, Denmark
| | - Morven Graham
- Center for Cellular and Molecular Imaging, Yale School of Medicine, New Haven, United States
| | - Xinran Liu
- Center for Cellular and Molecular Imaging, Yale School of Medicine, New Haven, United States.,Department of Cell Biology, Yale School of Medicine, New Haven, United States
| | - Christer S Ejsing
- Department of Biochemistry and Molecular Biology, VILLUM Center for Bioanalytical Sciences, University of Southern Denmark, Odense, Denmark
| | - Robert V Farese
- Department of Genetics and Complex Diseases, Harvard T.H. Chan School of Public Health, Boston, United States.,Department of Cell Biology, Harvard Medical School, Boston, United States.,Broad Institute, Cambridge, United States
| | - Tobias C Walther
- Department of Genetics and Complex Diseases, Harvard T.H. Chan School of Public Health, Boston, United States.,Department of Cell Biology, Harvard Medical School, Boston, United States.,Broad Institute, Cambridge, United States.,Howard Hughes Medical Institute, Harvard T.H. Chan School of Public Health, Boston, United States
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84
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Proia RL, Hla T. Emerging biology of sphingosine-1-phosphate: its role in pathogenesis and therapy. J Clin Invest 2015; 125:1379-87. [PMID: 25831442 DOI: 10.1172/jci76369] [Citation(s) in RCA: 388] [Impact Index Per Article: 43.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Membrane sphingolipids are metabolized to sphingosine-1-phosphate (S1P), a bioactive lipid mediator that regulates many processes in vertebrate development, physiology, and pathology. Once exported out of cells by cell-specific transporters, chaperone-bound S1P is spatially compartmentalized in the circulatory system. Extracellular S1P interacts with five GPCRs that are widely expressed and transduce intracellular signals to regulate cellular behavior, such as migration, adhesion, survival, and proliferation. While many organ systems are affected, S1P signaling is essential for vascular development, neurogenesis, and lymphocyte trafficking. Recently, a pharmacological S1P receptor antagonist has won approval to control autoimmune neuroinflammation in multiple sclerosis. The availability of pharmacological tools as well as mouse genetic models has revealed several physiological actions of S1P and begun to shed light on its pathological roles. The unique mode of signaling of this lysophospholipid mediator is providing novel opportunities for therapeutic intervention, with possibilities to target not only GPCRs but also transporters, metabolic enzymes, and chaperones.
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85
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Tu-Sekine B, Goldschmidt H, Raben DM. Diacylglycerol, phosphatidic acid, and their metabolic enzymes in synaptic vesicle recycling. Adv Biol Regul 2014; 57:147-52. [PMID: 25446883 DOI: 10.1016/j.jbior.2014.09.010] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Revised: 09/03/2014] [Accepted: 09/03/2014] [Indexed: 01/10/2023]
Abstract
The synaptic vesicle (SV) cycle includes exocytosis of vesicles loaded with a neurotransmitter such as glutamate, coordinated recovery of SVs by endocytosis, refilling of vesicles, and subsequent release of the refilled vesicles from the presynaptic bouton. SV exocytosis is tightly linked with endocytosis, and variations in the number of vesicles, and/or defects in the refilling of SVs, will affect the amount of neurotransmitter available for release (Sudhof, 2004). There is increasing interest in the roles synaptic vesicle lipids and lipid metabolizing enzymes play in this recycling. Initial emphasis was placed on the role of polyphosphoinositides in SV cycling as outlined in a number of reviews (Lim and Wenk, 2009; Martin, 2012; Puchkov and Haucke, 2013; Rohrbough and Broadie, 2005). Other lipids are now recognized to also play critical roles. For example, PLD1 (Humeau et al., 2001; Rohrbough and Broadie, 2005) and some DGKs (Miller et al., 1999; Nurrish et al., 1999) play roles in neurotransmission which is consistent with the critical roles for phosphatidic acid (PtdOH) and diacylglycerol (DAG) in the regulation of SV exo/endocytosis (Cremona et al., 1999; Exton, 1994; Huttner and Schmidt, 2000; Lim and Wenk, 2009; Puchkov and Haucke, 2013; Rohrbough and Broadie, 2005). PLD generates phosphatidic acid by catalyzing the hydrolysis of phosphatidylcholine (PtdCho) and in some systems this PtdOH is de-phosphorylated to generate DAG. In contrast, DGK catalyzes the phosphorylation of DAG thereby converting it into PtdOH. While both enzymes are poised to regulate the levels of DAG and PtdOH, therefore, they both lead to the generation of PtdOH and could have opposite effects on DAG levels. This is particularly important for SV cycling as PtdOH and DAG are both needed for evoked exocytosis (Lim and Wenk, 2009; Puchkov and Haucke, 2013; Rohrbough and Broadie, 2005). Two lipids and their involved metabolic enzymes, two sphingolipids have also been implicated in exocytosis: sphingosine (Camoletto et al., 2009; Chan et al., 2012; Chan and Sieburth, 2012; Darios et al., 2009; Kanno et al., 2010; Rohrbough et al., 2004) and sphingosine-1-phosphate (Chan, Hu, 2012; Chan and Sieburth, 2012; Kanno et al., 2010). Finally a number of reports have focused on the somewhat less well studies roles of sphingolipids and cholesterol in SV cycling. In this report, we review the recent understanding of the roles PLDs, DGKs, and DAG lipases, as well as sphingolipids and cholesterol play in synaptic vesicle cycling.
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Affiliation(s)
- Becky Tu-Sekine
- The Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Hana Goldschmidt
- The Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Daniel M Raben
- The Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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