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Bresgen N, Kovacs M, Lahnsteiner A, Felder TK, Rinnerthaler M. The Janus-Faced Role of Lipid Droplets in Aging: Insights from the Cellular Perspective. Biomolecules 2023; 13:912. [PMID: 37371492 DOI: 10.3390/biom13060912] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Revised: 05/22/2023] [Accepted: 05/29/2023] [Indexed: 06/29/2023] Open
Abstract
It is widely accepted that nine hallmarks-including mitochondrial dysfunction, epigenetic alterations, and loss of proteostasis-exist that describe the cellular aging process. Adding to this, a well-described cell organelle in the metabolic context, namely, lipid droplets, also accumulates with increasing age, which can be regarded as a further aging-associated process. Independently of their essential role as fat stores, lipid droplets are also able to control cell integrity by mitigating lipotoxic and proteotoxic insults. As we will show in this review, numerous longevity interventions (such as mTOR inhibition) also lead to strong accumulation of lipid droplets in Saccharomyces cerevisiae, Caenorhabditis elegans, Drosophila melanogaster, and mammalian cells, just to name a few examples. In mammals, due to the variety of different cell types and tissues, the role of lipid droplets during the aging process is much more complex. Using selected diseases associated with aging, such as Alzheimer's disease, Parkinson's disease, type II diabetes, and cardiovascular disease, we show that lipid droplets are "Janus"-faced. In an early phase of the disease, lipid droplets mitigate the toxicity of lipid peroxidation and protein aggregates, but in a later phase of the disease, a strong accumulation of lipid droplets can cause problems for cells and tissues.
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Affiliation(s)
- Nikolaus Bresgen
- Department of Biosciences and Medical Biology, Paris-Lodron University Salzburg, 5020 Salzburg, Austria
| | - Melanie Kovacs
- Department of Biosciences and Medical Biology, Paris-Lodron University Salzburg, 5020 Salzburg, Austria
| | - Angelika Lahnsteiner
- Department of Biosciences and Medical Biology, Paris-Lodron University Salzburg, 5020 Salzburg, Austria
| | - Thomas Klaus Felder
- Department of Laboratory Medicine, Paracelsus Medical University, 5020 Salzburg, Austria
| | - Mark Rinnerthaler
- Department of Biosciences and Medical Biology, Paris-Lodron University Salzburg, 5020 Salzburg, Austria
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Rix J, Uckermann O, Kirsche K, Schackert G, Koch E, Kirsch M, Galli R. Correlation of biomechanics and cancer cell phenotype by combined Brillouin and Raman spectroscopy of U87-MG glioblastoma cells. JOURNAL OF THE ROYAL SOCIETY, INTERFACE 2022; 19:20220209. [PMID: 35857926 DOI: 10.1098/rsif.2022.0209] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The elucidation of biomechanics furthers our understanding of brain tumour biology. Brillouin spectroscopy is a new optical method that addresses viscoelastic properties down to subcellular resolution in a contact-free manner. Moreover, it can be combined with Raman spectroscopy to obtain co-localized biochemical information. Here, we applied co-registered Brillouin and Raman spectroscopy to U87-MG human glioblastoma cells in vitro. Using two-dimensional and three-dimensional cultures, we related biomechanical properties to local biochemical composition at the subcellular level, as well as the cell phenotype. Brillouin and Raman mapping of adherent cells showed that the nucleus and nucleoli are stiffer than the perinuclear region and the cytoplasm. The biomechanics of the cell cytoplasm is affected by culturing conditions, i.e. cells grown as spheroids are stiffer than adherent cells. Inside the spheroids, the presence of lipid droplets as assessed by Raman spectroscopy revealed higher Brillouin shifts that are not related to a local increase in stiffness, but are due to a higher refractive index combined with a lower mass density. This highlights the importance of locally defined biochemical reference data for a correct interpretation of the Brillouin shift of cells and tissues in future studies investigating the biomechanics of brain tumour models by Brillouin spectroscopy.
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Affiliation(s)
- Jan Rix
- Clinical Sensoring and Monitoring, Department of Anesthesiology and Intensive Care Medicine, Faculty of Medicine Carl Gustav Carus, TU Dresden, Fetscherstrasse 74, D-01307 Dresden, Germany
| | - Ortrud Uckermann
- Neurosurgery, Faculty of Medicine Carl Gustav Carus, TU Dresden, Fetscherstrasse 74, D-01307 Dresden, Germany.,Division of Medical Biology, Department of Psychiatry, Faculty of Medicine and University Hospital Carl Gustav Carus, TU Dresden, Fetscherstrasse 74, D-01307 Dresden, Germany
| | - Katrin Kirsche
- Neurosurgery, Faculty of Medicine Carl Gustav Carus, TU Dresden, Fetscherstrasse 74, D-01307 Dresden, Germany
| | - Gabriele Schackert
- Neurosurgery, Faculty of Medicine Carl Gustav Carus, TU Dresden, Fetscherstrasse 74, D-01307 Dresden, Germany
| | - Edmund Koch
- Clinical Sensoring and Monitoring, Department of Anesthesiology and Intensive Care Medicine, Faculty of Medicine Carl Gustav Carus, TU Dresden, Fetscherstrasse 74, D-01307 Dresden, Germany
| | - Matthias Kirsch
- Neurosurgery, Faculty of Medicine Carl Gustav Carus, TU Dresden, Fetscherstrasse 74, D-01307 Dresden, Germany.,Klinik für Neurochirurgie, Asklepios Kliniken Schildautal, Karl-Herold-Strasse 1, D-38723 Seesen, Germany.,National Center for Tumor Diseases (NCT), Partner Site Dresden, Fetscherstrasse 74, D-01307 Dresden, Germany
| | - Roberta Galli
- Department of Medical Physics and Biomedical Engineering, Faculty of Medicine Carl Gustav Carus, TU Dresden, Fetscherstrasse 74, D-01307 Dresden, Germany
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Welte MA, Gould AP. Lipid droplet functions beyond energy storage. Biochim Biophys Acta Mol Cell Biol Lipids 2017; 1862:1260-1272. [PMID: 28735096 PMCID: PMC5595650 DOI: 10.1016/j.bbalip.2017.07.006] [Citation(s) in RCA: 337] [Impact Index Per Article: 48.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Revised: 07/17/2017] [Accepted: 07/17/2017] [Indexed: 02/07/2023]
Abstract
Lipid droplets are cytoplasmic organelles that store neutral lipids and are critically important for energy metabolism. Their function in energy storage is firmly established and increasingly well characterized. However, emerging evidence indicates that lipid droplets also play important and diverse roles in the cellular handling of lipids and proteins that may not be directly related to energy homeostasis. Lipid handling roles of droplets include the storage of hydrophobic vitamin and signaling precursors, and the management of endoplasmic reticulum and oxidative stress. Roles of lipid droplets in protein handling encompass functions in the maturation, storage, and turnover of cellular and viral polypeptides. Other potential roles of lipid droplets may be connected with their intracellular motility and, in some cases, their nuclear localization. This diversity highlights that lipid droplets are very adaptable organelles, performing different functions in different biological contexts. This article is part of a Special Issue entitled: Recent Advances in Lipid Droplet Biology edited by Rosalind Coleman and Matthijs Hesselink.
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Affiliation(s)
- Michael A Welte
- Department of Biology, University of Rochester, Rochester, NY, United States.
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Extending calibration-free force measurements to optically-trapped rod-shaped samples. Sci Rep 2017; 7:42960. [PMID: 28220855 PMCID: PMC5318951 DOI: 10.1038/srep42960] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Accepted: 01/17/2017] [Indexed: 12/14/2022] Open
Abstract
Optical trapping has become an optimal choice for biological research at the microscale due to its non-invasive performance and accessibility for quantitative studies, especially on the forces involved in biological processes. However, reliable force measurements depend on the calibration of the optical traps, which is different for each experiment and hence requires high control of the local variables, especially of the trapped object geometry. Many biological samples have an elongated, rod-like shape, such as chromosomes, intracellular organelles (e.g., peroxisomes), membrane tubules, certain microalgae, and a wide variety of bacteria and parasites. This type of samples often requires several optical traps to stabilize and orient them in the correct spatial direction, making it more difficult to determine the total force applied. Here, we manipulate glass microcylinders with holographic optical tweezers and show the accurate measurement of drag forces by calibration-free direct detection of beam momentum. The agreement between our results and slender-body hydrodynamic theoretical calculations indicates potential for this force-sensing method in studying protracted, rod-shaped specimens.
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Nanoscopic imaging of thick heterogeneous soft-matter structures in aqueous solution. Nat Commun 2016; 7:12729. [PMID: 27596919 PMCID: PMC5025867 DOI: 10.1038/ncomms12729] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Accepted: 07/27/2016] [Indexed: 01/28/2023] Open
Abstract
Precise nanometre-scale imaging of soft structures at room temperature poses a major challenge to any type of microscopy because fast thermal fluctuations lead to significant motion blur if the position of the structure is measured with insufficient bandwidth. Moreover, precise localization is also affected by optical heterogeneities, which lead to deformations in the imaged local geometry, the severity depending on the sample and its thickness. Here we introduce quantitative thermal noise imaging, a three-dimensional scanning probe technique, as a method for imaging soft, optically heterogeneous and porous matter with submicroscopic spatial resolution in aqueous solution. By imaging both individual microtubules and collagen fibrils in a network, we demonstrate that structures can be localized with a precision of ∼10 nm and that their local dynamics can be quantified with 50 kHz bandwidth and subnanometre amplitudes. Furthermore, we show how image distortions caused by optically dense structures can be corrected for. Integration time limits the capacity of super-resolution microscopy to study dynamics. Here, Bartsch et al. use the 3D scanning of a nanoparticle held in an optical trap, and its thermal noise motion within the trap, to image the local dynamics of soft-matter structures with a 50 kHz bandwidth.
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Load-induced enhancement of Dynein force production by LIS1-NudE in vivo and in vitro. Nat Commun 2016; 7:12259. [PMID: 27489054 PMCID: PMC4976208 DOI: 10.1038/ncomms12259] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Accepted: 06/15/2016] [Indexed: 01/01/2023] Open
Abstract
Most sub-cellular cargos are transported along microtubules by kinesin and dynein molecular motors, but how transport is regulated is not well understood. It is unknown whether local control is possible, for example, by changes in specific cargo-associated motor behaviour to react to impediments. Here we discover that microtubule-associated lipid droplets (LDs) in COS1 cells respond to an optical trap with a remarkable enhancement in sustained force production. This effect is observed only for microtubule minus-end-moving LDs. It is specifically blocked by RNAi for the cytoplasmic dynein regulators LIS1 and NudE/L (Nde1/Ndel1), but not for the dynactin p150Glued subunit. It can be completely replicated using cell-free preparations of purified LDs, where duration of LD force production is more than doubled. These results identify a novel, intrinsic, cargo-associated mechanism for dynein-mediated force adaptation, which should markedly improve the ability of motor-driven cargoes to overcome subcellular obstacles. Transport of large cargo through the cytoplasm can encounter physical impediments which should be overcome. Here the authors show that lipid droplets constrained by an optical trap respond with an increase in dynein-mediated force that is dependent on dynein regulators LIS1 and NudE/L, but not on p150glued.
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Welte MA. As the fat flies: The dynamic lipid droplets of Drosophila embryos. Biochim Biophys Acta Mol Cell Biol Lipids 2015; 1851:1156-85. [PMID: 25882628 DOI: 10.1016/j.bbalip.2015.04.002] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Revised: 03/31/2015] [Accepted: 04/06/2015] [Indexed: 01/09/2023]
Abstract
Research into lipid droplets is rapidly expanding, and new cellular and organismal roles for these lipid-storage organelles are continually being discovered. The early Drosophila embryo is particularly well suited for addressing certain questions in lipid-droplet biology and combines technical advantages with unique biological phenomena. This review summarizes key features of this experimental system and the techniques available to study it, in order to make it accessible to researchers outside this field. It then describes the two topics most heavily studied in this system, lipid-droplet motility and protein sequestration on droplets, discusses what is known about the molecular players involved, points to open questions, and compares the results from Drosophila embryo studies to what it is known about lipid droplets in other systems.
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Affiliation(s)
- Michael A Welte
- Department of Biology University of Rochester, RC Box 270211, 317 Hutchison Hall, Rochester, NY 14627, USA.
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Barak P, Rai A, Dubey AK, Rai P, Mallik R. Reconstitution of microtubule-dependent organelle transport. Methods Enzymol 2014; 540:231-48. [PMID: 24630110 DOI: 10.1016/b978-0-12-397924-7.00013-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Microtubule (MT)-based motor proteins transport many cellular factors to their functionally relevant locations within cells, and defects in transport are linked to human disease. Understanding the mechanism and regulation of this transport process in living cells is difficult because of the complex in vivo environment and limited means to manipulate the system. On the other hand, in vitro motility assays using purified motors attached to beads does not recapitulate the full complexity of cargo transport in vivo. Assaying motility of organelles in cell extracts is therefore attractive, as natural cargoes are being examined, but in an environment that is more amenable to manipulation. Here, we describe the purification and in vitro MT-based motility of phagosomes from Dictyostelium and lipid droplets from rat liver. These assays have the potential to address diverse questions related to endosome/phagosome maturation, fatty acid regulation, and could also serve as a starting point for reconstituting the motility of other types of organelles.
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Affiliation(s)
- Pradeep Barak
- Department of Biological Sciences, Tata Institute of Fundamental Research, Colaba, Mumbai, Maharashtra, India
| | - Ashim Rai
- Department of Biological Sciences, Tata Institute of Fundamental Research, Colaba, Mumbai, Maharashtra, India
| | - Alok Kumar Dubey
- Department of Biological Sciences, Tata Institute of Fundamental Research, Colaba, Mumbai, Maharashtra, India
| | - Priyanka Rai
- Department of Biological Sciences, Tata Institute of Fundamental Research, Colaba, Mumbai, Maharashtra, India
| | - Roop Mallik
- Department of Biological Sciences, Tata Institute of Fundamental Research, Colaba, Mumbai, Maharashtra, India.
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