1
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Obaseki E, Adebayo D, Bandyopadhyay S, Hariri H. Lipid droplets and fatty acid-induced lipotoxicity: in a nutshell. FEBS Lett 2024; 598:1207-1214. [PMID: 38281809 PMCID: PMC11126361 DOI: 10.1002/1873-3468.14808] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Revised: 12/02/2023] [Accepted: 01/04/2024] [Indexed: 01/30/2024]
Abstract
Lipid droplets (LDs) are fat storage organelles that are conserved from bacteria to humans. LDs are broken down to supply cells with fatty acids (FAs) that can be used as an energy source or membrane synthesis. An overload of FAs disrupts cellular functions and causes lipotoxicity. Thus, by acting as hubs for storing excess fat, LDs prevent lipotoxicity and preserve cellular homeostasis. LD synthesis and turnover have to be precisely regulated to maintain a balanced lipid distribution and allow for cellular adaptation during stress. Here, we discuss how prolonged exposure to excess lipids affects cellular functions, and the roles of LDs in buffering cellular stress focusing on lipotoxicity.
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Affiliation(s)
- Eseiwi Obaseki
- Department of Biological Sciences, Wayne State University, Detroit, MI, USA
| | - Daniel Adebayo
- Department of Biological Sciences, Wayne State University, Detroit, MI, USA
| | | | - Hanaa Hariri
- Department of Biological Sciences, Wayne State University, Detroit, MI, USA
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2
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Girik V, Feng S, Hariri H, Henne WM, Riezman H. Vacuole-Specific Lipid Release for Tracking Intracellular Lipid Metabolism and Transport in Saccharomyces cerevisiae. ACS Chem Biol 2022; 17:1485-1494. [PMID: 35667650 PMCID: PMC9207805 DOI: 10.1021/acschembio.2c00120] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Lipid metabolism is spatiotemporally regulated within cells, yet intervention into lipid functions at subcellular resolution remains difficult. Here, we report a method that enables site-specific release of sphingolipids and cholesterol inside the vacuole in Saccharomyces cerevisiae. Using this approach, we monitored real-time sphingolipid metabolic flux out of the vacuole by mass spectrometry and found that the endoplasmic reticulum-vacuole-tethering protein Mdm1 facilitated the metabolism of sphingoid bases into ceramides. In addition, we showed that cholesterol, once delivered into yeast using our method, could restore cell proliferation induced by ergosterol deprivation, overcoming the previously described sterol-uptake barrier under aerobic conditions. Together, these data define a new way to study intracellular lipid metabolism and transport from the vacuole in yeast.
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Affiliation(s)
- Vladimir Girik
- Department of Biochemistry, University of Geneva, Geneva 1205, Switzerland
| | - Suihan Feng
- Department of Biochemistry, University of Geneva, Geneva 1205, Switzerland.,National Centre of Competence in Research (NCCR) in Chemical Biology, University of Geneva, Geneva 1205, Switzerland
| | - Hanaa Hariri
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, Texas 75390-9039 United States
| | - W Mike Henne
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, Texas 75390-9039 United States
| | - Howard Riezman
- Department of Biochemistry, University of Geneva, Geneva 1205, Switzerland
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3
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Abstract
SNX-RGS proteins are molecular tethers localized to multiple interorganelle contact sites that exhibit roles in cellular metabolism. Here, we highlight recent findings on these proteins and discuss their emerging roles in metabolism, human disease, and lipid trafficking.
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Affiliation(s)
- Hanaa Hariri
- Department of Biological Sciences, Wayne State University, Detroit, MI
| | - W. Mike Henne
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX
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4
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Paul B, Weeratunga S, Tillu VA, Hariri H, Henne WM, Collins BM. Structural Predictions of the SNX-RGS Proteins Suggest They Belong to a New Class of Lipid Transfer Proteins. Front Cell Dev Biol 2022; 10:826688. [PMID: 35223850 PMCID: PMC8864675 DOI: 10.3389/fcell.2022.826688] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 01/13/2022] [Indexed: 12/12/2022] Open
Abstract
Recent advances in protein structure prediction using machine learning such as AlphaFold2 and RosettaFold presage a revolution in structural biology. Genome-wide predictions of protein structures are providing unprecedented insights into their architecture and intradomain interactions, and applications have already progressed towards assessing protein complex formation. Here we present detailed analyses of the sorting nexin proteins that contain regulator of G-protein signalling domains (SNX-RGS proteins), providing a key example of the ability of AlphaFold2 to reveal novel structures with previously unsuspected biological functions. These large proteins are conserved in most eukaryotes and are known to associate with lipid droplets (LDs) and sites of LD-membrane contacts, with key roles in regulating lipid metabolism. They possess five domains, including an N-terminal transmembrane domain that anchors them to the endoplasmic reticulum, an RGS domain, a lipid interacting phox homology (PX) domain and two additional domains named the PXA and PXC domains of unknown structure and function. Here we report the crystal structure of the RGS domain of sorting nexin 25 (SNX25) and show that the AlphaFold2 prediction closely matches the experimental structure. Analysing the full-length SNX-RGS proteins across multiple homologues and species we find that the distant PXA and PXC domains in fact fold into a single unique structure that notably features a large and conserved hydrophobic pocket. The nature of this pocket strongly suggests a role in lipid or fatty acid binding, and we propose that these molecules represent a new class of conserved lipid transfer proteins.
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Affiliation(s)
- Blessy Paul
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, Australia
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Saroja Weeratunga
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, Australia
| | - Vikas A. Tillu
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, Australia
| | - Hanaa Hariri
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - W. Mike Henne
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Brett M. Collins
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, Australia
- *Correspondence: Brett M. Collins,
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5
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Renne MF, Hariri H. Lipid Droplet-Organelle Contact Sites as Hubs for Fatty Acid Metabolism, Trafficking, and Metabolic Channeling. Front Cell Dev Biol 2021; 9:726261. [PMID: 34595176 PMCID: PMC8477659 DOI: 10.3389/fcell.2021.726261] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Accepted: 08/12/2021] [Indexed: 01/21/2023] Open
Abstract
Cells prepare for fluctuations in nutrient availability by storing energy in the form of neutral lipids in organelles called Lipid Droplets (LDs). Upon starvation, fatty acids (FAs) released from LDs are trafficked to different cellular compartments to be utilized for membrane biogenesis or as a source of energy. Despite the biochemical pathways being known in detail, the spatio-temporal regulation of FA synthesis, storage, release, and breakdown is not completely understood. Recent studies suggest that FA trafficking and metabolism are facilitated by inter-organelle contact sites that form between LDs and other cellular compartments such as the Endoplasmic Reticulum (ER), mitochondria, peroxisomes, and lysosomes. LD-LD contact sites are also sites where FAs are transferred in a directional manner to support LD growth and expansion. As the storage site of neutral lipids, LDs play a central role in FA homeostasis. In this mini review, we highlight the role of LD contact sites with other organelles in FA trafficking, channeling, and metabolism and discuss the implications for these pathways on cellular lipid and energy homeostasis.
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Affiliation(s)
- Mike F. Renne
- Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom
| | - Hanaa Hariri
- Department of Biological Sciences, Wayne State University, Detroit, MI, United States
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6
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Kontakis MG, Diez-Escudero A, Hariri H, Andersson B, Järhult JD, Hailer NP. Antimicrobial and osteoconductive properties of two different types of titanium silver coating. Eur Cell Mater 2021; 41:694-706. [PMID: 34121171 DOI: 10.22203/ecm.v041a45] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
In prosthetic joint surgery, Ag coating of implant areas in direct contact with bone has been met with hesitation for fear of compromising osseointegration. The physicochemical, antibacterial and osteoconductive properties of three different Ti samples were studied: Ti6Al4V alloy that was grit-blasted (GB), Ti6Al4V alloy with an experimental Ti-Ag-nitride layer (SN) applied by physical vapour deposition (PVD) and commercially available PVD-coated Ti6Al4V alloy with a base Ag layer and a surface Ti-Ag-nitride layer (SSN, clinically known as PorAg®). Ag content on the surface of experimental SN and SSN discs was 27.7 %wt and 68.5 % wt, respectively. At 28 d, Ag release was 4 ppm from SN and 26.9 ppm from SSN substrates. Colonisation of discs by Staphylococcus aureus was the highest on GB [944 (± 91) × 10 4 CFU/mL], distinctly lower on experimental SN discs [414 (± 117) × 104 CFU/mL] and the lowest on SSN discs [307 (± 126) × 10 4 CFU/mL]. Primary human osteoblasts were abundant 28 d after seeding on GB discs but their adhesion and differentiation, measured by alkaline-phosphatase production, was suppressed by 73 % on SN and by 96 % on SSN discs, in comparison to GB discs. Thus, the PVD-applied Ag coatings differed considerably in their antibacterial effects and osteoconductivity. The experimental SN coating had similar antibacterial effects to the commercially available SSN coating while providing slightly improved osteoconductivity. Balancing the Ag content of Ti implants will be vital for future developments of implants designed for cementless fixation into bone.
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7
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Abstract
The intimate relationships between cell fate and metabolism have long been recognized, but a mechanistic understanding of how metabolic pathways are dynamically regulated during development and disease, how they interact with signalling pathways, and how they affect differential gene expression is only emerging now. We summarize the key findings and the major themes that emerged from the virtual Keystone Symposium 'Metabolic Decisions in Development and Disease' held in March 2021.
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Affiliation(s)
- Lluc Mosteiro
- Department of Discovery Oncology, Genentech, South San Francisco, CA 94080, USA
| | - Hanaa Hariri
- Department of Biological Sciences, Wayne State University, Detroit, MI 48202, USA
| | - Jelle van den Ameele
- Department of Clinical Neurosciences and MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, UK
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8
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Rogers S, Hariri H, Wood NE, Speer NO, Henne WM. Glucose restriction drives spatial reorganization of mevalonate metabolism. eLife 2021; 10:62591. [PMID: 33825684 PMCID: PMC8057812 DOI: 10.7554/elife.62591] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2020] [Accepted: 04/06/2021] [Indexed: 01/01/2023] Open
Abstract
Eukaryotes compartmentalize metabolic pathways into sub-cellular domains, but the role of inter-organelle contacts in organizing metabolic reactions remains poorly understood. Here, we show that in response to acute glucose restriction (AGR) yeast undergo metabolic remodeling of their mevalonate pathway that is spatially coordinated at nucleus-vacuole junctions (NVJs). The NVJ serves as a metabolic platform by selectively retaining HMG-CoA Reductases (HMGCRs), driving mevalonate pathway flux in an Upc2-dependent manner. Both spatial retention of HMGCRs and increased mevalonate pathway flux during AGR is dependent on NVJ tether Nvj1. Furthermore, we demonstrate that HMGCRs associate into high-molecular-weight assemblies during AGR in an Nvj1-dependent manner. Loss of Nvj1-mediated HMGCR partitioning can be bypassed by artificially multimerizing HMGCRs, indicating NVJ compartmentalization enhances mevalonate pathway flux by promoting the association of HMGCRs in high molecular weight assemblies. Loss of HMGCR compartmentalization perturbs yeast growth following glucose starvation, indicating it promotes adaptive metabolic remodeling. Collectively, we propose a non-canonical mechanism regulating mevalonate metabolism via the spatial compartmentalization of rate-limiting HMGCR enzymes at an inter-organelle contact site.
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Affiliation(s)
- Sean Rogers
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, United States
| | - Hanaa Hariri
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Biological Sciences, Wayne State University, Detroit, United States
| | - N Ezgi Wood
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, United States
| | - Natalie Ortiz Speer
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, United States
| | - W Mike Henne
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, United States
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9
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Henne M, Goodman JM, Hariri H. Spatial compartmentalization of lipid droplet biogenesis. Biochim Biophys Acta Mol Cell Biol Lipids 2020; 1865:158499. [PMID: 31352131 PMCID: PMC7050823 DOI: 10.1016/j.bbalip.2019.07.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Revised: 07/08/2019] [Accepted: 07/09/2019] [Indexed: 12/18/2022]
Abstract
Lipid droplets (LDs) are ubiquitous organelles that store metabolic energy in the form of neutral lipids (typically triacylglycerols and steryl esters). Beyond being inert energy storage compartments, LDs are dynamic organelles that participate in numerous essential metabolic functions. Cells generate LDs de novo from distinct sub-regions at the endoplasmic reticulum (ER), but what determines sites of LD formation remains a key unanswered question. Here, we review the factors that determine LD formation at the ER, and discuss how they work together to spatially and temporally coordinate LD biogenesis. These factors include lipid synthesis enzymes, assembly proteins, and membrane structural requirements. LDs also make contact with other organelles, and these inter-organelle contacts contribute to defining sites of LD production. Finally, we highlight emerging non-canonical roles for LDs in maintaining cellular homeostasis during stress.
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Affiliation(s)
- Mike Henne
- Department of Cell Biology and Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, United States of America
| | - Joel M Goodman
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX, United States of America
| | - Hanaa Hariri
- Department of Cell Biology and Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, United States of America.
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10
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Ugrankar R, Bowerman J, Hariri H, Chandra M, Chen K, Bossanyi MF, Datta S, Rogers S, Eckert KM, Vale G, Victoria A, Fresquez J, McDonald JG, Jean S, Collins BM, Henne WM. Drosophila Snazarus Regulates a Lipid Droplet Population at Plasma Membrane-Droplet Contacts in Adipocytes. Dev Cell 2019; 50:557-572.e5. [PMID: 31422916 PMCID: PMC7446143 DOI: 10.1016/j.devcel.2019.07.021] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Revised: 04/22/2019] [Accepted: 07/17/2019] [Indexed: 01/22/2023]
Abstract
Adipocytes store nutrients as lipid droplets (LDs), but how they organize their LD stores to balance lipid uptake, storage, and mobilization remains poorly understood. Here, using Drosophila fat body (FB) adipocytes, we characterize spatially distinct LD populations that are maintained by different lipid pools. We identify peripheral LDs (pLDs) that make close contact with the plasma membrane (PM) and are maintained by lipophorin-dependent lipid trafficking. pLDs are distinct from larger cytoplasmic medial LDs (mLDs), which are maintained by FASN1-dependent de novo lipogenesis. We find that sorting nexin CG1514 or Snazarus (Snz) associates with pLDs and regulates LD homeostasis at ER-PM contact sites. Loss of SNZ perturbs pLD organization, whereas Snz over-expression drives LD expansion, triacylglyceride production, starvation resistance, and lifespan extension through a DESAT1-dependent pathway. We propose that Drosophila adipocytes maintain spatially distinct LD populations and identify Snz as a regulator of LD organization and inter-organelle crosstalk.
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Affiliation(s)
- Rupali Ugrankar
- Department of Cell Biology, UT Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, TX 75390, USA
| | - Jade Bowerman
- Department of Cell Biology, UT Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, TX 75390, USA
| | - Hanaa Hariri
- Department of Cell Biology, UT Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, TX 75390, USA
| | - Mintu Chandra
- Institute for Molecular Bioscience, the University of Queensland, St. Lucia, QLD 4072, Australia
| | - Kevin Chen
- Institute for Molecular Bioscience, the University of Queensland, St. Lucia, QLD 4072, Australia
| | - Marie-France Bossanyi
- Department of Anatomy and Cell Biology, University of Sherbrooke, 2500 Boulevard de l'Universite, Sherbrooke, QC J1K 2R1, Canada
| | - Sanchari Datta
- Department of Cell Biology, UT Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, TX 75390, USA
| | - Sean Rogers
- Department of Cell Biology, UT Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, TX 75390, USA
| | - Kaitlyn M Eckert
- Center for Human Nutrition, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Gonçalo Vale
- Center for Human Nutrition, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Alexia Victoria
- Department of Cell Biology, UT Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, TX 75390, USA
| | | | - Jeffrey G McDonald
- Center for Human Nutrition, UT Southwestern Medical Center, Dallas, TX 75390, USA; Department of Molecular Genetics, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Steve Jean
- Department of Anatomy and Cell Biology, University of Sherbrooke, 2500 Boulevard de l'Universite, Sherbrooke, QC J1K 2R1, Canada
| | - Brett M Collins
- Institute for Molecular Bioscience, the University of Queensland, St. Lucia, QLD 4072, Australia
| | - W Mike Henne
- Department of Cell Biology, UT Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, TX 75390, USA.
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11
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Hariri H, Speer N, Bowerman J, Rogers S, Fu G, Reetz E, Datta S, Feathers JR, Ugrankar R, Nicastro D, Henne WM. Mdm1 maintains endoplasmic reticulum homeostasis by spatially regulating lipid droplet biogenesis. J Cell Biol 2019; 218:1319-1334. [PMID: 30808705 PMCID: PMC6446837 DOI: 10.1083/jcb.201808119] [Citation(s) in RCA: 78] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Revised: 01/10/2019] [Accepted: 01/22/2019] [Indexed: 12/13/2022] Open
Abstract
Excess fatty acids are toxic to cells but can be sequestered as triacylglycerides in lipid droplets. Hariri et al. show that the tethering protein Mdm1 spatially regulates this process at the junction between the endoplasmic reticulum and the yeast vacuole. These findings suggest that Mdm1 can drive spatially defined lipid droplet production to maintain cell homeostasis and protect against lipotoxicity. Lipid droplets (LDs) serve as cytoplasmic reservoirs for energy-rich fatty acids (FAs) stored in the form of triacylglycerides (TAGs). During nutrient stress, yeast LDs cluster adjacent to the vacuole/lysosome, but how this LD accumulation is coordinated remains poorly understood. The ER protein Mdm1 is a molecular tether that plays a role in clustering LDs during nutrient depletion, but its mechanism of function remains unknown. Here, we show that Mdm1 associates with LDs through its hydrophobic N-terminal region, which is sufficient to demarcate sites for LD budding. Mdm1 binds FAs via its Phox-associated domain and coenriches with fatty acyl–coenzyme A ligase Faa1 at LD bud sites. Consistent with this, loss of MDM1 perturbs free FA activation and Dga1-dependent synthesis of TAGs, elevating the cellular FA level, which perturbs ER morphology and sensitizes yeast to FA-induced lipotoxicity. We propose that Mdm1 coordinates FA activation adjacent to the vacuole to promote LD production in response to stress, thus maintaining ER homeostasis.
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Affiliation(s)
- Hanaa Hariri
- Department of Cell Biology and Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX
| | - Natalie Speer
- Department of Cell Biology and Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX
| | - Jade Bowerman
- Department of Cell Biology and Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX
| | - Sean Rogers
- Department of Cell Biology and Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX
| | - Gang Fu
- Department of Cell Biology and Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX
| | - Evan Reetz
- Department of Cell Biology and Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX
| | - Sanchari Datta
- Department of Cell Biology and Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX
| | - J Ryan Feathers
- Department of Cell Biology and Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX
| | - Rupali Ugrankar
- Department of Cell Biology and Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX
| | - Daniela Nicastro
- Department of Cell Biology and Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX
| | - W Mike Henne
- Department of Cell Biology and Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX
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12
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Bryant D, Liu Y, Datta S, Hariri H, Seda M, Anderson G, Peskett E, Demetriou C, Sousa S, Jenkins D, Clayton P, Bitner-Glindzicz M, Moore GE, Henne WM, Stanier P. SNX14 mutations affect endoplasmic reticulum-associated neutral lipid metabolism in autosomal recessive spinocerebellar ataxia 20. Hum Mol Genet 2019; 27:1927-1940. [PMID: 29635513 DOI: 10.1093/hmg/ddy101] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Accepted: 03/15/2018] [Indexed: 12/12/2022] Open
Abstract
Mutations in SNX14 cause the autosomal recessive cerebellar ataxia 20 (SCAR20). Mutations generally result in loss of protein although several coding region deletions have also been reported. Patient-derived fibroblasts show disrupted autophagy, but the precise function of SNX14 is unknown. The yeast homolog, Mdm1, functions in endoplasmic reticulum (ER)-lysosome/vacuole inter-organelle tethering, but functional conservation in mammals is still required. Here, we show that loss of SNX14 alters but does not block autophagic flux. In addition, we find that SNX14 is an ER-associated protein that functions in neutral lipid homeostasis and inter-organelle crosstalk. SNX14 requires its N-terminal transmembrane helices for ER localization, while the Phox homology (PX) domain is dispensable for subcellular localization. Both SNX14-mutant fibroblasts and SNX14KO HEK293 cells accumulate aberrant cytoplasmic vacuoles, suggesting defects in endolysosomal homeostasis. However, ER-late endosome/lysosome contact sites are maintained in SNX14KO cells, indicating that it is not a prerequisite for ER-endolysosomal tethering. Further investigation of SNX14- deficiency indicates general defects in neutral lipid metabolism. SNX14KO cells display distinct perinuclear accumulation of filipin in LAMP1-positive lysosomal structures indicating cholesterol accumulation. Consistent with this, SNX14KO cells display a slight but detectable decrease in cholesterol ester levels, which is exacerbated with U18666A. Finally, SNX14 associates with ER-derived lipid droplets (LD) following oleate treatment, indicating a role in ER-LD crosstalk. We therefore identify an important role for SNX14 in neutral lipid homeostasis between the ER, lysosomes and LDs that may provide an early intervention target to alleviate the clinical symptoms of SCAR20.
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Affiliation(s)
- Dale Bryant
- Genetics and Genomic Medicine, UCL Great Ormond Street Institute of Child Health, London WC1N 1EH, UK
| | - Yang Liu
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Sanchari Datta
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Hanaa Hariri
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Marian Seda
- Genetics and Genomic Medicine, UCL Great Ormond Street Institute of Child Health, London WC1N 1EH, UK
| | - Glenn Anderson
- Histopathology Department, Great Ormond Street Hospital, London WC1N 3JH, UK
| | - Emma Peskett
- Genetics and Genomic Medicine, UCL Great Ormond Street Institute of Child Health, London WC1N 1EH, UK
| | - Charalambos Demetriou
- Genetics and Genomic Medicine, UCL Great Ormond Street Institute of Child Health, London WC1N 1EH, UK
| | - Sergio Sousa
- Serviço de Genética Medica, Hospital Pediatrico, Centro Hospitalar e Universitário de Coimbra, 3000-602 Coimbra, Portugal
| | - Dagan Jenkins
- Genetics and Genomic Medicine, UCL Great Ormond Street Institute of Child Health, London WC1N 1EH, UK
| | - Peter Clayton
- Genetics and Genomic Medicine, UCL Great Ormond Street Institute of Child Health, London WC1N 1EH, UK
| | - Maria Bitner-Glindzicz
- Genetics and Genomic Medicine, UCL Great Ormond Street Institute of Child Health, London WC1N 1EH, UK
| | - Gudrun E Moore
- Genetics and Genomic Medicine, UCL Great Ormond Street Institute of Child Health, London WC1N 1EH, UK
| | - W Mike Henne
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Philip Stanier
- Genetics and Genomic Medicine, UCL Great Ormond Street Institute of Child Health, London WC1N 1EH, UK
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13
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Datta S, Liu Y, Hariri H, Bowerman J, Henne WM. Cerebellar ataxia disease-associated Snx14 promotes lipid droplet growth at ER-droplet contacts. J Cell Biol 2019; 218:1335-1351. [PMID: 30765438 PMCID: PMC6446855 DOI: 10.1083/jcb.201808133] [Citation(s) in RCA: 76] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Revised: 12/29/2018] [Accepted: 01/28/2019] [Indexed: 01/22/2023] Open
Abstract
Lipid droplets (LDs) are nutrient reservoirs used by cells to maintain homeostasis. Nascent droplets form on the endoplasmic reticulum (ER) and grow following an influx of exogenous fatty acids (FAs). The budding of LDs requires extensive ER-LD crosstalk, but how this is regulated remains poorly understood. Here, we show that sorting nexin protein Snx14, an ER-resident protein associated with the cerebellar ataxia SCAR20, localizes to ER-LD contacts following FA treatment, where it promotes LD maturation. Using proximity-based APEX technology and topological dissection, we show that Snx14 accumulates specifically at ER-LD contacts independently of Seipin, where it remains ER-anchored and binds LDs in trans. SNX14KO cells exhibit perturbed LD morphology, whereas Snx14 overexpression promotes LD biogenesis and extends ER-LD contacts. Multi-time point imaging reveals that Snx14 is recruited to ER microdomains containing the fatty acyl-CoA ligase ACSL3, where nascent LDs bud. We propose that Snx14 is a novel marker for ER-LD contacts and regulates FA-stimulated LD growth.
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Affiliation(s)
- Sanchari Datta
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Yang Liu
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Hanaa Hariri
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Jade Bowerman
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX
| | - W Mike Henne
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX
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Abstract
Lipid droplets (LDs) serve as specialized cytoplasmic organelles that harbor energy-rich lipids for long-term storage and may be mobilized as nutrient sources during extended starvation. How cells coordinate LD biogenesis and utilization in response to fluctuations in nutrient availability remains poorly understood. Here, we discuss our recent work revealing how yeast spatially organize LD budding at organelle contacts formed between the endoplasmic reticulum and yeast vacuole/lysosome (sites known as nucleus-vacuole junctions [NVJs]). During times of imminent nutrient exhaustion, we observe blooms of stress-induced LDs surrounding the NVJ and find that this LD clustering is regulated by NVJ-resident protein Mdm1. We also discuss several emerging studies revealing specific proteins that demarcate a subpopulation of NVJ-associated LDs. Collectively, these studies reveal a previously unappreciated role for the spatial compartmentalization of LDs at organelle contacts and highlight an important role for interorganellar cross talk in LD dynamics under times of nutritional stress.
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Affiliation(s)
- W Mike Henne
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Hanaa Hariri
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX, USA
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Hariri H, Rogers S, Ugrankar R, Liu YL, Feathers JR, Henne WM. Lipid droplet biogenesis is spatially coordinated at ER-vacuole contacts under nutritional stress. EMBO Rep 2017; 19:57-72. [PMID: 29146766 DOI: 10.15252/embr.201744815] [Citation(s) in RCA: 113] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Revised: 10/12/2017] [Accepted: 10/23/2017] [Indexed: 12/20/2022] Open
Abstract
Eukaryotic cells store lipids in cytosolic organelles known as lipid droplets (LDs). Lipid droplet bud from the endoplasmic reticulum (ER), and may be harvested by the vacuole for energy during prolonged periods of starvation. How cells spatially coordinate LD production is poorly understood. Here, we demonstrate that yeast ER-vacuole contact sites (NVJs) physically expand in response to metabolic stress, and serve as sites for LD production. NVJ tether Mdm1 demarcates sites of LD budding, and interacts with fatty acyl-CoA synthases at the NVJ periphery. Artificially expanding the NVJ through over-expressing Mdm1 is sufficient to drive NVJ-associated LD production, whereas ablating the NVJ induces defects in fatty acid-to-triglyceride production. Collectively, our data suggest a tight metabolic link between nutritional stress and LD biogenesis that is spatially coordinated at ER-vacuole contact sites.
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Affiliation(s)
- Hanaa Hariri
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Sean Rogers
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Rupali Ugrankar
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Yang Lydia Liu
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX, USA
| | - J Ryan Feathers
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX, USA
| | - W Mike Henne
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX, USA
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16
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Hariri H, Ugrankar R, Liu Y, Henne WM. Inter-organelle ER-endolysosomal contact sites in metabolism and disease across evolution. Commun Integr Biol 2016; 9:e1156278. [PMID: 27489577 PMCID: PMC4951168 DOI: 10.1080/19420889.2016.1156278] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Accepted: 02/13/2016] [Indexed: 12/29/2022] Open
Abstract
Since their initial observation, contact sites formed between different organelles have transitioned from ignored curiosities to recognized centers for the exchange of metabolites and lipids. Contact formed between the ER and endomembrane system (eg. the plasma membrane, endosomes, and lysosomes) is of particular biomedical interest, as it governs aspects of lipid metabolism, organelle identity, and cell signaling. Here, we review the field of ER-endolysosomal communication from the perspective of three model systems: budding yeast, the fruit fly D. melanogaster, and mammals. From this broad perspective, inter-organelle communication displays a consistent role in metabolic regulation that was differentially tuned during the development of complex metazoan life. We also examine the current state of understanding of lipid exchange between organelles, and discuss molecular mechanisms by which this occurs.
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Affiliation(s)
- Hanaa Hariri
- Department of Cell Biology, UT Southwestern Medical Center , Dallas, TX, USA
| | - Rupali Ugrankar
- Department of Cell Biology, UT Southwestern Medical Center , Dallas, TX, USA
| | - Yang Liu
- Department of Cell Biology, UT Southwestern Medical Center , Dallas, TX, USA
| | - W Mike Henne
- Department of Cell Biology, UT Southwestern Medical Center , Dallas, TX, USA
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Lowry TW, Hariri H, Prommapan P, Kusi-Appiah A, Vafai N, Bienkiewicz EA, Van Winkle DH, Stagg SM, Lenhert S. Quantification of Protein-Induced Membrane Remodeling Kinetics In Vitro with Lipid Multilayer Gratings. Small 2016; 12:506-15. [PMID: 26649649 PMCID: PMC4843995 DOI: 10.1002/smll.201502398] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Revised: 10/28/2015] [Indexed: 05/08/2023]
Abstract
The dynamic self-organization of lipids in biological systems is a highly regulated process that enables the compartmentalization of living systems at micro- and nanoscopic scales. Consequently, quantitative methods for assaying the kinetics of supramolecular remodeling such as vesicle formation from planar lipid bilayers or multilayers are needed to understand cellular self-organization. Here, a new nanotechnology-based method for quantitative measurements of lipid-protein interactions is presented and its suitability for quantifying the membrane binding, inflation, and budding activity of the membrane-remodeling protein Sar1 is demonstrated. Lipid multilayer gratings are printed onto surfaces using nanointaglio and exposed to Sar1, resulting in the inflation of lipid multilayers into unilamellar structures, which can be observed in a label-free manner by monitoring the diffracted light. Local variations in lipid multilayer volume on the surface is used to vary substrate availability in a microarray format. A quantitative model is developed that allows quantification of binding affinity (K D ) and kinetics (kon and koff ). Importantly, this assay is uniquely capable of quantifying membrane remodeling. Upon Sar1-induced inflation of single bilayers from surface supported multilayers, the semicylindrical grating lines are observed to remodel into semispherical buds when a critical radius of curvature is reached.
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Affiliation(s)
- Troy W. Lowry
- Department of Physics, Florida State University, Tallahassee, FL 32306-4350, USA
| | - Hanaa Hariri
- Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306-4380, USA
| | - Plengchart Prommapan
- Department of Physics, Florida State University, Tallahassee, FL 32306-4350, USA
| | - Aubrey Kusi-Appiah
- Department of Biological Science, Florida State University, Tallahassee, FL 32306-4370, USA
| | - Nicholas Vafai
- Department of Biological Science, Florida State University, Tallahassee, FL 32306-4370, USA
| | - Ewa A. Bienkiewicz
- Department of Biomedical Science, College of Medicine, Florida State University, Tallahassee, FL 32306-4300, USA
| | - David H. Van Winkle
- Department of Physics, Florida State University, Tallahassee, FL 32306-4350, USA
| | - Scott M. Stagg
- Institute of Molecular Biophysics and Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306-4380, USA
| | - Steven Lenhert
- Department of Biological Science and Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306-4370, USA
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19
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Hariri H, Farhat T, Khalaf R, Fahed A, Al-Haddad C, Arabi M, Bitar F, Nemer G. P569A novel role for NFATC1 in patients with both congenital heart disease and glaucoma. Cardiovasc Res 2014. [DOI: 10.1093/cvr/cvu098.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Kassab K, Hariri H, Fahed A, El-Rassi I, Bitar F, Nemer G. P329GATA5: a key player in congenital heart diseases. Cardiovasc Res 2014. [DOI: 10.1093/cvr/cvu091.16] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Noble AJ, Zhang Q, O'Donnell J, Hariri H, Bhattacharya N, Marshall AG, Stagg SM. A pseudoatomic model of the COPII cage obtained from cryo-electron microscopy and mass spectrometry. Nat Struct Mol Biol 2013; 20:167-73. [PMID: 23262493 PMCID: PMC3565055 DOI: 10.1038/nsmb.2467] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2012] [Accepted: 11/09/2012] [Indexed: 12/23/2022]
Abstract
COPII vesicles transport proteins from the endoplasmic reticulum to the Golgi apparatus. Previous COPII-cage cryo-EM structures lacked the resolution necessary to determine the residues of Sec13 and Sec31 that mediate assembly and flexibility of the COPII cage. Here we present a 12-Å structure of the human COPII cage, where the tertiary structure of Sec13 and Sec31 is clearly identifiable. We employ this structure and a homology model of the Sec13-Sec31 complex to create a reliable pseudoatomic model of the COPII cage. We combined this model with hydrogen/deuterium-exchange MS analysis to characterize four distinct contact regions at the vertices of the COPII cage. Furthermore, we found that the two-fold symmetry of the Sec31 dimeric region in Sec13-Sec31 is broken upon cage formation and that the resulting hinge is essential to form the proper edge geometry in COPII cages.
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Affiliation(s)
- Alex J Noble
- Department of Physics, Florida State University, Tallahassee, Florida, USA
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