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Subramanya AR, Boyd-Shiwarski CR. Molecular Crowding: Physiologic Sensing and Control. Annu Rev Physiol 2024; 86:429-452. [PMID: 37931170 DOI: 10.1146/annurev-physiol-042222-025920] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2023]
Abstract
The cytoplasm is densely packed with molecules that contribute to its nonideal behavior. Cytosolic crowding influences chemical reaction rates, intracellular water mobility, and macromolecular complex formation. Overcrowding is potentially catastrophic; to counteract this problem, cells have evolved acute and chronic homeostatic mechanisms that optimize cellular crowdedness. Here, we provide a physiology-focused overview of molecular crowding, highlighting contemporary advances in our understanding of its sensing and control. Long hypothesized as a form of crowding-induced microcompartmentation, phase separation allows cells to detect and respond to intracellular crowding through the action of biomolecular condensates, as indicated by recent studies. Growing evidence indicates that crowding is closely tied to cell size and fluid volume, homeostatic responses to physical compression and desiccation, tissue architecture, circadian rhythm, aging, transepithelial transport, and total body electrolyte and water balance. Thus, molecular crowding is a fundamental physiologic parameter that impacts diverse functions extending from molecule to organism.
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Affiliation(s)
- Arohan R Subramanya
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA; ,
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
- Pittsburgh Center for Kidney Research, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
- VA Pittsburgh Healthcare System, Pittsburgh, Pennsylvania, USA
| | - Cary R Boyd-Shiwarski
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA; ,
- Pittsburgh Center for Kidney Research, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
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2
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Boyd-Shiwarski CR, Shiwarski DJ, Griffiths SE, Beacham RT, Norrell L, Morrison DE, Wang J, Mann J, Tennant W, Anderson EN, Franks J, Calderon M, Connolly KA, Cheema MU, Weaver CJ, Nkashama LJ, Weckerly CC, Querry KE, Pandey UB, Donnelly CJ, Sun D, Rodan AR, Subramanya AR. WNK kinases sense molecular crowding and rescue cell volume via phase separation. Cell 2022; 185:4488-4506.e20. [PMID: 36318922 PMCID: PMC9699283 DOI: 10.1016/j.cell.2022.09.042] [Citation(s) in RCA: 54] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 07/23/2022] [Accepted: 09/29/2022] [Indexed: 11/24/2022]
Abstract
When challenged by hypertonicity, dehydrated cells must recover their volume to survive. This process requires the phosphorylation-dependent regulation of SLC12 cation chloride transporters by WNK kinases, but how these kinases are activated by cell shrinkage remains unknown. Within seconds of cell exposure to hypertonicity, WNK1 concentrates into membraneless condensates, initiating a phosphorylation-dependent signal that drives net ion influx via the SLC12 cotransporters to restore cell volume. WNK1 condensate formation is driven by its intrinsically disordered C terminus, whose evolutionarily conserved signatures are necessary for efficient phase separation and volume recovery. This disorder-encoded phase behavior occurs within physiological constraints and is activated in vivo by molecular crowding rather than changes in cell size. This allows kinase activity despite an inhibitory ionic milieu and permits cell volume recovery through condensate-mediated signal amplification. Thus, WNK kinases are physiological crowding sensors that phase separate to coordinate a cell volume rescue response.
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Affiliation(s)
- Cary R Boyd-Shiwarski
- Department of Medicine, Renal-Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Pittsburgh Center for Kidney Research, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Daniel J Shiwarski
- Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Shawn E Griffiths
- Department of Medicine, Renal-Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Rebecca T Beacham
- Department of Medicine, Renal-Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Logan Norrell
- Molecular Medicine Program, University of Utah, Salt Lake City, UT 84132, USA
| | - Daryl E Morrison
- Molecular Medicine Program, University of Utah, Salt Lake City, UT 84132, USA
| | - Jun Wang
- Department of Neurology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Jacob Mann
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - William Tennant
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Eric N Anderson
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Jonathan Franks
- Center for Biological Imaging, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Michael Calderon
- Center for Biological Imaging, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Kelly A Connolly
- Department of Medicine, Renal-Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Muhammad Umar Cheema
- Department of Medicine, Renal-Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Claire J Weaver
- Department of Medicine, Renal-Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Lubika J Nkashama
- Department of Medicine, Renal-Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Claire C Weckerly
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Katherine E Querry
- Department of Medicine, Renal-Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Udai Bhan Pandey
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Center for Protein Conformational Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Christopher J Donnelly
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Center for Protein Conformational Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Dandan Sun
- Department of Neurology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; VA Pittsburgh Healthcare System, Pittsburgh, PA 15240, USA
| | - Aylin R Rodan
- Department of Human Genetics, University of Utah, Salt Lake City, UT 84132, USA; Molecular Medicine Program, University of Utah, Salt Lake City, UT 84132, USA; Department of Internal Medicine, Division of Nephrology and Hypertension, University of Utah, Salt Lake City, UT 84132, USA; Medical Service, VA Salt Lake City Health Care System, Salt Lake City, UT 84148, USA
| | - Arohan R Subramanya
- Department of Medicine, Renal-Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Center for Protein Conformational Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; Pittsburgh Center for Kidney Research, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA; VA Pittsburgh Healthcare System, Pittsburgh, PA 15240, USA.
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3
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Lecinski S, Shepherd JW, Frame L, Hayton I, MacDonald C, Leake MC. Investigating molecular crowding during cell division and hyperosmotic stress in budding yeast with FRET. CURRENT TOPICS IN MEMBRANES 2021; 88:75-118. [PMID: 34862033 PMCID: PMC7612257 DOI: 10.1016/bs.ctm.2021.09.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Cell division, aging, and stress recovery triggers spatial reorganization of cellular components in the cytoplasm, including membrane bound organelles, with molecular changes in their compositions and structures. However, it is not clear how these events are coordinated and how they integrate with regulation of molecular crowding. We use the budding yeast Saccharomyces cerevisiae as a model system to study these questions using recent progress in optical fluorescence microscopy and crowding sensing probe technology. We used a Förster Resonance Energy Transfer (FRET) based sensor, illuminated by confocal microscopy for high throughput analyses and Slimfield microscopy for single-molecule resolution, to quantify molecular crowding. We determine crowding in response to cellular growth of both mother and daughter cells, in addition to osmotic stress, and reveal hot spots of crowding across the bud neck in the burgeoning daughter cell. This crowding might be rationalized by the packing of inherited material, like the vacuole, from mother cells. We discuss recent advances in understanding the role of crowding in cellular regulation and key current challenges and conclude by presenting our recent advances in optimizing FRET-based measurements of crowding while simultaneously imaging a third color, which can be used as a marker that labels organelle membranes. Our approaches can be combined with synchronized cell populations to increase experimental throughput and correlate molecular crowding information with different stages in the cell cycle.
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Affiliation(s)
- Sarah Lecinski
- Department of Physics, University of York, York, United Kingdom
| | - Jack W Shepherd
- Department of Physics, University of York, York, United Kingdom; Department of Biology, University of York, York, United Kingdom
| | - Lewis Frame
- School of Natural Sciences, University of York, York, United Kingdom
| | - Imogen Hayton
- Department of Biology, University of York, York, United Kingdom
| | - Chris MacDonald
- Department of Biology, University of York, York, United Kingdom
| | - Mark C Leake
- Department of Physics, University of York, York, United Kingdom; Department of Biology, University of York, York, United Kingdom.
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4
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Jalihal AP, Schmidt A, Gao G, Little SR, Pitchiaya S, Walter NG. Hyperosmotic phase separation: Condensates beyond inclusions, granules and organelles. J Biol Chem 2021; 296:100044. [PMID: 33168632 PMCID: PMC7948973 DOI: 10.1074/jbc.rev120.010899] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 11/06/2020] [Accepted: 11/09/2020] [Indexed: 01/09/2023] Open
Abstract
Biological liquid-liquid phase separation has gained considerable attention in recent years as a driving force for the assembly of subcellular compartments termed membraneless organelles. The field has made great strides in elucidating the molecular basis of biomolecular phase separation in various disease, stress response, and developmental contexts. Many important biological consequences of such "condensation" are now emerging from in vivo studies. Here we review recent work from our group and others showing that many proteins undergo rapid, reversible condensation in the cellular response to ubiquitous environmental fluctuations such as osmotic changes. We discuss molecular crowding as an important driver of condensation in these responses and suggest that a significant fraction of the proteome is poised to undergo phase separation under physiological conditions. In addition, we review methods currently emerging to visualize, quantify, and modulate the dynamics of intracellular condensates in live cells. Finally, we propose a metaphor for rapid phase separation based on cloud formation, reasoning that our familiar experiences with the readily reversible condensation of water droplets help understand the principle of phase separation. Overall, we provide an account of how biological phase separation supports the highly intertwined relationship between the composition and dynamic internal organization of cells, thus facilitating extremely rapid reorganization in response to internal and external fluctuations.
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Affiliation(s)
- Ameya P Jalihal
- Single Molecule Analysis Group and Center for RNA Biomedicine, Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA; Cell and Molecular Biology Graduate Program, University of Michigan, Ann Arbor, Michigan, USA
| | - Andreas Schmidt
- Single Molecule Analysis Group and Center for RNA Biomedicine, Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA
| | - Guoming Gao
- Single Molecule Analysis Group and Center for RNA Biomedicine, Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA; Biophysics Graduate Program, University of Michigan, Ann Arbor, Michigan, USA
| | - Saffron R Little
- Single Molecule Analysis Group and Center for RNA Biomedicine, Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA; Program in Chemical Biology, University of Michigan, Ann Arbor, Michigan, USA
| | - Sethuramasundaram Pitchiaya
- Michigan Center for Translational Pathology, University of Michigan Medical School, Ann Arbor, Michigan, USA; Department of Pathology, University of Michigan, Ann Arbor, Michigan, USA
| | - Nils G Walter
- Single Molecule Analysis Group and Center for RNA Biomedicine, Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA.
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5
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Rana PS, Kurokawa M, Model MA. Evidence for macromolecular crowding as a direct apoptotic stimulus. J Cell Sci 2020; 133:jcs243931. [PMID: 32393677 PMCID: PMC7240305 DOI: 10.1242/jcs.243931] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Accepted: 03/13/2020] [Indexed: 12/13/2022] Open
Abstract
Potassium loss and persistent shrinkage have both been implicated in apoptosis but their relationship and respective roles remain controversial. We approached this problem by clamping intracellular sodium and potassium in HeLa or MDCK cells using a combination of ionophores. Although ionophore treatment caused significant cell swelling, the initial volume could be restored and further reduced by application of sucrose. The swollen cells treated with ionophores remained viable for at least 8 h without any signs of apoptosis. Application of sucrose and the resulting shrinkage caused volume-dependent intrinsic apoptosis with all its classical features: inversion of phosphatidylserine, caspase activation and Bcl-2-dependent release of cytochrome c from mitochondria. In other experiments, apoptosis was induced by addition of the protein kinase inhibitor staurosporine at various degrees of swelling. Our results show that: (1) persistent shrinkage can cause apoptosis regardless of intracellular sodium or potassium composition or of the state of actin cytoskeleton; (2) strong potassium dependence of caspase activation is only observed in swollen cells with a reduced density of cytosolic proteins. We conclude that macromolecular crowding can be an important factor in determining the transition of cells to apoptosis.
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Affiliation(s)
- Priyanka S Rana
- Department of Biological Sciences, Kent State University, Kent, OH 44242, USA
| | - Manabu Kurokawa
- Department of Biological Sciences, Kent State University, Kent, OH 44242, USA
| | - Michael A Model
- Department of Biological Sciences, Kent State University, Kent, OH 44242, USA
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6
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Norris OC, Schermerhorn T. The mean cell volume difference (dMCV) reflects serum hypertonicity in diabetic dogs. PLoS One 2019; 14:e0219864. [PMID: 31335875 PMCID: PMC6650031 DOI: 10.1371/journal.pone.0219864] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Accepted: 07/02/2019] [Indexed: 12/29/2022] Open
Abstract
Serum hypertonicity may develop during diabetes mellitus due to hyperglycemia and other biochemical changes. Hypertonicity may produce detrimental cellular and systemic effects and has been identified as a serum marker for some clinical disorders. In non-diabetic dogs, the mean cell volume difference, a novel erythrocyte measure, is increased by serum hypertonicity. However, it is not known whether hyperglycemic hypertonicity produces a similar change. The hypothesis that the mean cell volume difference could detect serum hypertonicity in diabetes was investigated in a group of thirty-two dogs with naturally-occurring diabetes mellitus that were prospectively recruited over a 1-year period from the outpatient population of a veterinary teaching hospital. The effect of hyperglycemia on the mean cell volume difference and the ability of the mean cell volume difference to predict serum hypertonicity were examined. Serum hyperosmolality and hypertonicity due to hyperglycemia was present in 91% and 94% of dogs, respectively. Hyperglycemia was the principal cause identified for serum hypertonicity and hyperosmolality. Using a cut-off value of ≥ 3 μm3 for the mean cell volume difference, serum hypertonicity ≥ 320 mmol/kg was identified with 79% sensitivity and 61% specificity. The dMCV correlated with changes in serum glucose, tonicity, and measured osmolality. Dogs with a mean cell volume difference ≥ 3 μm3 were at risk for serum tonicity ≥ 320 mmol/kg (risk ratio = 2.2) and serum glucose ≥ 13.9 mmol/L (risk ratio = 2.3). In conclusion, the mean cell volume difference is a useful surrogate marker for detecting serum hypertonicity in diabetic dogs and elevated mean cell volume difference is associated with increased risks for clinically relevant serum hypertonicity and hyperglycemia.
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Affiliation(s)
- Olga C. Norris
- Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas, United States of America
| | - Thomas Schermerhorn
- Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas, United States of America
- * E-mail:
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7
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8
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Kulikova-Borovikova D, Lisi S, Dauss E, Alamae T, Buzzini P, Hallsworth JE, Rapoport A. Activity of the α-glucoside transporter Agt1 in Saccharomyces cerevisiae cells during dehydration-rehydration events. Fungal Biol 2018; 122:613-620. [PMID: 29801806 DOI: 10.1016/j.funbio.2018.03.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Revised: 03/14/2018] [Accepted: 03/16/2018] [Indexed: 11/26/2022]
Abstract
Microbial cells can enter a state of anhydrobiosis under desiccating conditions. One of the main determinants of viability during dehydration-rehydration cycles is structural integrity of the plasma membrane. Whereas much is known about phase transitions of the lipid bilayer, there is a paucity of information on changes in activity of plasma membrane proteins during dehydration-rehydration events. We selected the α-glucoside transporter Agt1 to gain insights into stress mechanisms/responses and ecophysiology during anhydrobiosis. As intracellular water content of S. cerevisiae strain 14 (a strain with moderate tolerance to dehydration-rehydration) was reduced to 1.5 g water/g dry weight, the activity of the Agt1 transporter decreased by 10-15 %. This indicates that functionality of this trans-membrane and relatively hydrophobic protein depends on water. Notably, however, levels of cell viability were retained. Prior incubation in the stress protectant xylitol increased stability of the plasma membrane but not Agt1. Studies were carried out using a comparator yeast which was highly resistant to dehydration-rehydration (S. cerevisiae strain 77). By contrast to S. cerevisiae strain 14, there was no significant reduction of Agt1 activity in S. cerevisiae strain 77 cells. These findings have implications for the ecophysiology of S. cerevisiae strains in natural and industrial systems.
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Affiliation(s)
- Diana Kulikova-Borovikova
- Laboratory of Cell Biology, Institute of Microbiology and Biotechnology, University of Latvia, Jelgavas Str., 1-537, LV-1004, Riga, Latvia
| | - Silvia Lisi
- Department of Agricultural, Food and Environmental Science & Industrial Yeasts Collection DBVPG, University of Perugia, Borgo XX Giugno 74, I-06121, Perugia, Italy
| | - Edgars Dauss
- Laboratory of Cell Biology, Institute of Microbiology and Biotechnology, University of Latvia, Jelgavas Str., 1-537, LV-1004, Riga, Latvia
| | - Tiina Alamae
- Department of Genetics, Institute of Molecular and Cell Biology, University of Tartu, Riia 23, 51010, Tartu, Estonia
| | - Pietro Buzzini
- Department of Agricultural, Food and Environmental Science & Industrial Yeasts Collection DBVPG, University of Perugia, Borgo XX Giugno 74, I-06121, Perugia, Italy
| | - John E Hallsworth
- Institute for Global Food Security, School of Biological Sciences, MBC, Queen's University Belfast, Belfast, BT9 7BL, Northern Ireland, UK
| | - Alexander Rapoport
- Laboratory of Cell Biology, Institute of Microbiology and Biotechnology, University of Latvia, Jelgavas Str., 1-537, LV-1004, Riga, Latvia.
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El-Chami C, Haslam IS, Steward MC, O'Neill CA. Organic osmolytes preserve the function of the developing tight junction in ultraviolet B-irradiated rat epidermal keratinocytes. Sci Rep 2018; 8:5167. [PMID: 29581434 PMCID: PMC5979960 DOI: 10.1038/s41598-018-22533-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Accepted: 02/08/2018] [Indexed: 01/04/2023] Open
Abstract
Epidermal barrier function is provided by the highly keratinised stratum corneum and also by tight junctions (TJs) in the granular layer of skin. The development of the TJ barrier significantly deteriorates in response to ultraviolet B radiation (UVB). Following exposure to UVB, keratinocytes accumulate organic osmolytes, which are known to preserve cell volume during water stress. Since TJs are intimately associated with control of water homeostasis in skin, we hypothesised that there may be a direct influence of osmolytes on TJ development. Exposure of rat epidermal keratinocytes (REKs) to a single dose of UVB reduced the function of developing TJs. This was concomitant with dislocalisation of claudin-1 and claudin-4 from the keratinocyte plasma membrane, phosphorylation of occludin and elevation of reactive oxygen species (ROS). In the presence of organic osmolytes, these effects were negated but were independent of the effects of these molecules on cell volume, elevation of ROS or the gene expression of TJ proteins. These data suggest that organic osmolytes affect TJs via post-translational mechanism(s) possibly involving protection of the native conformation of TJ proteins.
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Affiliation(s)
- Cécile El-Chami
- School of Biological Sciences, Division of Musculoskeletal & Dermatological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Oxford Road, Manchester, M13 9PT, United Kingdom
| | - Iain S Haslam
- School of Biological Sciences, Division of Musculoskeletal & Dermatological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Oxford Road, Manchester, M13 9PT, United Kingdom.,School of Medical Sciences, Division of Diabetes, Endocrinology and Gastroenterology, Faculty of Biology, Medicine and Health, University of Manchester, Oxford Road, Manchester, M13 9PT, United Kingdom.,Department of Biological Sciences, School of Applied Sciences, University of Huddersfield, Queensgate, Huddersfield, HD1 3DH, United Kingdom
| | - Martin C Steward
- School of Medical Sciences, Division of Diabetes, Endocrinology and Gastroenterology, Faculty of Biology, Medicine and Health, University of Manchester, Oxford Road, Manchester, M13 9PT, United Kingdom
| | - Catherine A O'Neill
- School of Biological Sciences, Division of Musculoskeletal & Dermatological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Oxford Road, Manchester, M13 9PT, United Kingdom.
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10
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An Aversive Response to Osmotic Upshift in Caenorhabditis elegans. eNeuro 2017; 4:eN-NWR-0282-16. [PMID: 28451641 PMCID: PMC5399755 DOI: 10.1523/eneuro.0282-16.2017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Revised: 03/16/2017] [Accepted: 03/20/2017] [Indexed: 12/12/2022] Open
Abstract
Environmental osmolarity presents a common type of sensory stimulus to animals. While behavioral responses to osmotic changes are important for maintaining a stable intracellular osmolarity, the underlying mechanisms are not fully understood. In the natural habitat of Caenorhabditis elegans, changes in environmental osmolarity are commonplace. It is known that the nematode acutely avoids shocks of extremely high osmolarity. Here, we show that C. elegans also generates gradually increased aversion of mild upshifts in environmental osmolarity. Different from an acute avoidance of osmotic shocks that depends on the function of a transient receptor potential vanilloid channel, the slow aversion to osmotic upshifts requires the cGMP-gated sensory channel subunit TAX-2. TAX-2 acts in several sensory neurons that are exposed to body fluid to generate the aversive response through a motor network that underlies navigation. Osmotic upshifts activate the body cavity sensory neuron URX, which is known to induce aversion upon activation. Together, our results characterize the molecular and cellular mechanisms underlying a novel sensorimotor response to osmotic stimuli and reveal that C. elegans engages different behaviors and the underlying mechanisms to regulate responses to extracellular osmolarity.
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11
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Osaka T. Hypothermia induced by inhibition of fatty acid metabolism in anesthetized rats: contributions of the forebrain and vagal afferents. Can J Physiol Pharmacol 2017; 95:652-660. [PMID: 28177663 DOI: 10.1139/cjpp-2016-0195] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
2-Mercaptoacetate (MA) is an antimetabolic drug that inhibits the utilization of fatty acids as an energy source. The intravenous injection of MA (1.2 mmol·kg-1) elicited an increase in tail skin temperature and a decrease in body core temperature in urethane-chloralose-anesthetized, neuromuscularly blocked, artificially ventilated rats, although administration of the same amount of NaCl did not. The respiratory exchange ratio was significantly higher after administration of MA than that after the saline treatment. On the other hand, heat production was increased by either the MA- or NaCl-injection, suggesting a nonspecific effect caused by the hyperosmolality of the solutions. These results indicate that the MA-induced hypothermia was caused by an increase in heat loss but not by a decrease in heat production. The amplitudes of heat loss responses to MA in rats fasted overnight were significantly smaller than those in fed ones, suggesting a mechanism for suppression of heat loss in the fasted state. Rats pretreated with vagotomy, capsaicin-induced desensitization of sensory nerve fibers or decerebration did not exhibit the MA-induced hypothermic responses. It is possible that the MA-induced heat loss and hypothermia were mediated by the vagal afferents and required the forebrain for the full expression of the responses.
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Affiliation(s)
- Toshimasa Osaka
- Department of Nutritional Science, National Institute of Health and Nutrition, 1-23-1 Toyama, Shinjuku 162-8636, Japan.,Department of Nutritional Science, National Institute of Health and Nutrition, 1-23-1 Toyama, Shinjuku 162-8636, Japan
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12
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Sévin DC, Stählin JN, Pollak GR, Kuehne A, Sauer U. Global Metabolic Responses to Salt Stress in Fifteen Species. PLoS One 2016; 11:e0148888. [PMID: 26848578 PMCID: PMC4743995 DOI: 10.1371/journal.pone.0148888] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 01/25/2016] [Indexed: 11/18/2022] Open
Abstract
Cells constantly adapt to unpredictably changing extracellular solute concentrations. A cornerstone of the cellular osmotic stress response is the metabolic supply of energy and building blocks to mount appropriate defenses. Yet, the extent to which osmotic stress impinges on the metabolic network remains largely unknown. Moreover, it is mostly unclear which, if any, of the metabolic responses to osmotic stress are conserved among diverse organisms or confined to particular groups of species. Here we investigate the global metabolic responses of twelve bacteria, two yeasts and two human cell lines exposed to sustained hyperosmotic salt stress by measuring semiquantitative levels of hundreds of cellular metabolites using nontargeted metabolomics. Beyond the accumulation of osmoprotectants, we observed significant changes of numerous metabolites in all species. Global metabolic responses were predominantly species-specific, yet individual metabolites were characteristically affected depending on species’ taxonomy, natural habitat, envelope structure or salt tolerance. Exploiting the breadth of our dataset, the correlation of individual metabolite response magnitudes across all species implicated lower glycolysis, tricarboxylic acid cycle, branched-chain amino acid metabolism and heme biosynthesis to be generally important for salt tolerance. Thus, our findings place the global metabolic salt stress response into a phylogenetic context and provide insights into the cellular phenotype associated with salt tolerance.
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Affiliation(s)
- Daniel C. Sévin
- Institute of Molecular Systems Biology, ETH Zürich, Zurich, Switzerland
- PhD Program on Systems Biology, Life Science Zurich, Zurich, Switzerland
- * E-mail: (US); (DCS)
| | | | - Georg R. Pollak
- Institute of Molecular Systems Biology, ETH Zürich, Zurich, Switzerland
| | - Andreas Kuehne
- Institute of Molecular Systems Biology, ETH Zürich, Zurich, Switzerland
- PhD Program on Systems Biology, Life Science Zurich, Zurich, Switzerland
| | - Uwe Sauer
- Institute of Molecular Systems Biology, ETH Zürich, Zurich, Switzerland
- * E-mail: (US); (DCS)
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13
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Reinhart JM, Yancey MR, Pohlman LM, Schermerhorn T. Evaluation of mean corpuscular volume difference as a marker for serum hypertonicity during water deprivation in dogs. Am J Vet Res 2015; 76:170-3. [PMID: 25629915 DOI: 10.2460/ajvr.76.2.170] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To evaluate mean corpuscular volume difference (dMCV) as a marker for hypertonicity induced by water deprivation in dogs. ANIMALS 5 healthy Greyhounds maintained in a research colony. PROCEDURES Water was withheld for 24 hours. Blood and urine samples were collected before (time 0) and every 6 hours during water deprivation. Serum and urine osmolality were measured on the basis of freezing point depression, and dMCV was calculated from routine hematologic variables. RESULTS Serum and urine osmolality significantly increased and body weight decreased over time in healthy Greyhounds during water deprivation, although most dogs developed only a slight increase in serum osmolality. The dMCV also increased over time, but the value at 24 hours did not differ significantly from the value at time 0. However, a significant correlation was found between serum osmolality and dMCV. A dMCV ≥ 5 fL yielded 100% specificity for predicting hypertonicity when hypertonicity was defined as serum osmolality ≥ 310 mOsM. CONCLUSIONS AND CLINICAL RELEVANCE dMCV may be a useful marker for detection of mild hypertonicity in dogs and may have clinical and research applications for use in screening canine populations for hypertonicity.
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Affiliation(s)
- Jennifer M Reinhart
- Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506
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Reinhart JM, Yancey MR, Girard-Denton JD, Schermerhorn T. Determination of tonicity effects of ketoacids and lactate by use of two canine red blood cell assays. Am J Vet Res 2015; 76:77-83. [PMID: 25535664 DOI: 10.2460/ajvr.76.1.77] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To determine the tonicity effects of β-hydroxybutyrate, acetoacetate, and lactate in canine RBCs. SAMPLE RBCs from approximately 40 dogs. PROCEDURES 2 in vitro methods were used to conduct 4 experiments. The modified osmotic fragility assay was used to measure the ability of ketoacid salts added to serial sucrose dilutions to protect RBCs from osmotic hemolysis. In a second assay, a handheld cell counting device was used to measure changes in RBC diameter to assess the tonicity effect of solutions of ketoacid and lactate salts. RESULTS For the modified osmotic fragility assay, all ketoacid salts had an osmoprotective effect, but the effect was determined to be completely attributable to the tonicity effect of added cations (sodium and lithium) and not the ketoacid moieties. However, both the sodium and lithium lactate salts provided osmoprotection attributable to both the cation and lactate anion. For the second assay, RBC diameter was significantly increased with the addition of urea (an ineffective osmole) but did not change with the addition of glucose (an effective osmole), which established the behaviors of ineffective and effective osmoles in this assay. The RBC diameter was significantly increased over that of control samples by the addition of sodium β-hydroxybutyrate, lithium acetoacetate, and lithium lactate but was decreased by the addition of sodium lactate. CONCLUSIONS AND CLINICAL RELEVANCE For both assays, β-hydroxybutyrate and acetoacetate acted as ineffective osmoles, whereas lactate acted as an effective osmole in 3 of 4 experiments.
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Affiliation(s)
- Jennifer M Reinhart
- Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506
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Villarreal FD, Kültz D. Direct Ionic Regulation of the Activity of Myo-Inositol Biosynthesis Enzymes in Mozambique Tilapia. PLoS One 2015; 10:e0123212. [PMID: 26066044 PMCID: PMC4466255 DOI: 10.1371/journal.pone.0123212] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Accepted: 02/28/2015] [Indexed: 11/27/2022] Open
Abstract
Myo-inositol (Ins) is a major compatible osmolyte in many cells, including those of Mozambique tilapia (Oreochromis mossambicus). Ins biosynthesis is highly up-regulated in tilapia and other euryhaline fish exposed to hyperosmotic stress. In this study, enzymatic regulation of two enzymes of Ins biosynthesis, Ins phosphate synthase (MIPS) and inositol monophosphatase (IMPase), by direct ionic effects is analyzed. Specific MIPS and IMPase isoforms from Mozambique tilapia (MIPS-160 and IMPase 1) were selected based on experimental, phylogenetic, and structural evidence supporting their role for Ins biosynthesis during hyperosmotic stress. Recombinant tilapia IMPase 1 and MIPS-160 activity was assayed in vitro at ionic conditions that mimic changes in the intracellular milieu during hyperosmotic stress. The in vitro activities of MIPS-160 and IMPase 1 are highest at alkaline pH of 8.8. IMPase 1 catalytic efficiency is strongly increased during hyperosmolality (particularly for the substrate D-Ins-3-phosphate, Ins-3P), mainly as a result of [Na+] elevation. Furthermore, the substrate-specificity of IMPase 1 towards D-Ins-1-phosphate (Ins-1P) is lower than towards Ins-3P. Because MIPS catalysis results in Ins-3P this results represents additional evidence for IMPase 1 being the isoform that mediates Ins biosynthesis in tilapia. Our data collectively demonstrate that the Ins biosynthesis enzymes are activated under ionic conditions that cells are exposed to during hypertonicity, resulting in Ins accumulation, which, in turn, results in restoration of intracellular ion homeostasis. We propose that the unique and direct ionic regulation of the activities of Ins biosynthesis enzymes represents an efficient biochemical feedback loop for regulation of intracellular physiological ion homeostasis during hyperosmotic stress.
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Affiliation(s)
- Fernando D. Villarreal
- EcoPhysiological Proteomics Laboratory, Department of Animal Science, University of California Davis, One Shields Avenue, Davis, California 95616, United States of America
| | - Dietmar Kültz
- EcoPhysiological Proteomics Laboratory, Department of Animal Science, University of California Davis, One Shields Avenue, Davis, California 95616, United States of America
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Ionic imbalance, in addition to molecular crowding, abates cytoskeletal dynamics and vesicle motility during hypertonic stress. Proc Natl Acad Sci U S A 2015; 112:E3104-13. [PMID: 26045497 DOI: 10.1073/pnas.1421290112] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Cell volume homeostasis is vital for the maintenance of optimal protein density and cellular function. Numerous mammalian cell types are routinely exposed to acute hypertonic challenge and shrink. Molecular crowding modifies biochemical reaction rates and decreases macromolecule diffusion. Cell volume is restored rapidly by ion influx but at the expense of elevated intracellular sodium and chloride levels that persist long after challenge. Although recent studies have highlighted the role of molecular crowding on the effects of hypertonicity, the effects of ionic imbalance on cellular trafficking dynamics in living cells are largely unexplored. By tracking distinct fluorescently labeled endosome/vesicle populations by live-cell imaging, we show that vesicle motility is reduced dramatically in a variety of cell types at the onset of hypertonic challenge. Live-cell imaging of actin and tubulin revealed similar arrested microfilament motility upon challenge. Vesicle motility recovered long after cell volume, a process that required functional regulatory volume increase and was accelerated by a return of extracellular osmolality to isosmotic levels. This delay suggests that, although volume-induced molecular crowding contributes to trafficking defects, it alone cannot explain the observed effects. Using fluorescent indicators and FRET-based probes, we found that intracellular ATP abundance and mitochondrial potential were reduced by hypertonicity and recovered after longer periods of time. Similar to the effects of osmotic challenge, isovolumetric elevation of intracellular chloride concentration by ionophores transiently decreased ATP production by mitochondria and abated microfilament and vesicle motility. These data illustrate how perturbed ionic balance, in addition to molecular crowding, affects membrane trafficking.
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Holzinger U, Brunner R, Losert H, Fuhrmann V, Herkner H, Madl C, Sterz F, Schneeweiß B. Resting energy expenditure and substrate oxidation rates correlate to temperature and outcome after cardiac arrest - a prospective observational cohort study. Crit Care 2015; 19:128. [PMID: 25888299 PMCID: PMC4404232 DOI: 10.1186/s13054-015-0856-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Accepted: 03/04/2015] [Indexed: 01/24/2023] Open
Abstract
INTRODUCTION Targeted temperature management improves outcome after cardiopulmonary resuscitation. Reduction of resting energy expenditure might be one mode of action. The aim of this study was to correlate resting energy expenditure and substrate oxidation rates with targeted temperature management at 33°C and outcome in patients after cardiac arrest. METHODS This prospective, observational cohort study was performed at the department of emergency medicine and a medical intensive care unit of a university hospital. Patients after successful cardiopulmonary resuscitation undergoing targeted temperature management at 33°C for 24 hours with subsequent rewarming to 36°C and standardized sedation, analgesic and paralytic medication were included. Indirect calorimetry was performed five times within 48 h after cardiac arrest. Measurements were correlated to outcome with repeated measures ANOVA, linear and logistic regression analysis. RESULTS In 25 patients resting energy expenditure decreased 20 (18 to 27) % at 33°C compared to 36°C without differences between outcome groups (favourable vs. unfavourable: 25 (21 to 26) vs. 21 (16 to 26); P = 0.5). In contrast to protein oxidation rate (favourable vs. unfavourable: 35 (11 to 68) g/day vs. 39 (7 to 75) g/day, P = 0.8) patients with favourable outcome had a significantly higher fat oxidation rate (139 (104 to 171) g/day vs. 117 (70 to 139) g/day, P <0.05) and a significantly lower glucose oxidation rate (30 (-34 to 88) g/day vs. 77 (19 to 138) g/day; P < 0.05) as compared to patients with unfavourable neurological outcome. CONCLUSIONS Targeted temperature management at 33°C after cardiac arrest reduces resting energy expenditure by 20% compared to 36°C. Glucose and fat oxidation rates differ significantly between patients with favourable and unfavourable neurological outcome. TRIAL REGISTRATION Clinicaltrials.gov NCT00500825. Registered 11 July 2007.
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Affiliation(s)
- Ulrike Holzinger
- Department of Medicine III, Division of Gastroenterology and Hepatology, ICU 13H1, Medical University of Vienna, Waehringer Guertel 18-20, Vienna, 1090, Austria.
| | - Richard Brunner
- Department of Medicine III, Division of Gastroenterology and Hepatology, ICU 13H1, Medical University of Vienna, Waehringer Guertel 18-20, Vienna, 1090, Austria.
| | - Heidrun Losert
- Department of Emergency Medicine, Medical University of Vienna, Waehringer Guertel 18-20, Vienna, 1090, Austria.
| | - Valentin Fuhrmann
- Department of Intensive Care, University Medical Center Hamburg-Eppendorf, Martinistraße 52, Hamburg, 20246, Germany.
| | - Harald Herkner
- Department of Emergency Medicine, Medical University of Vienna, Waehringer Guertel 18-20, Vienna, 1090, Austria.
| | - Christian Madl
- Department of Medicine III, Division of Gastroenterology and Hepatology, ICU 13H1, Medical University of Vienna, Waehringer Guertel 18-20, Vienna, 1090, Austria.
| | - Fritz Sterz
- Department of Emergency Medicine, Medical University of Vienna, Waehringer Guertel 18-20, Vienna, 1090, Austria.
| | - Bruno Schneeweiß
- Department of Medicine III, Division of Gastroenterology and Hepatology, ICU 13H1, Medical University of Vienna, Waehringer Guertel 18-20, Vienna, 1090, Austria.
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Dupont S, Rapoport A, Gervais P, Beney L. Survival kit of Saccharomyces cerevisiae for anhydrobiosis. Appl Microbiol Biotechnol 2014; 98:8821-34. [DOI: 10.1007/s00253-014-6028-5] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Revised: 08/08/2014] [Accepted: 08/10/2014] [Indexed: 01/08/2023]
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The effect of Arg on the structure perturbation and chaperone activity of α-crystallin in the presence of the crowding agent, dextran. Appl Biochem Biotechnol 2014; 174:739-50. [PMID: 25091326 DOI: 10.1007/s12010-014-1092-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Accepted: 07/21/2014] [Indexed: 10/24/2022]
Abstract
α-Crystallin is a protein that is expressed at high levels in all vertebrate eye lenses. It has a molecular weight of 20 kDa and is composed of two subunits: αA and αB. α-Crystallin is a member of the small heat shock protein (sHsps) family that has been shown to prevent protein aggregation. Small molecules are organic compounds that have low molecular weight (<800 Da). Arginin (Arg) is a small molecule and has been shown to prevent protein aggregation through interaction with partially folded intermediates. In this study, the effect of Arg on the chaperone activity of α-crystallin in the presence of dextran, as a crowding agent, against ordered and disordered aggregation of different target proteins (α-lactalbumin, ovotransferrin, and catalase) has been investigated. The experiments were done using visible absorption spectroscopy, ThT-binding assay, fluorescence spectroscopy, and CD spectroscopy. The results showed that in amorphous aggregation and amyloid fibril formation, both in the presence and absence of dextran, Arg had a positive effect on the chaperone action of α-crystallin. However, in the presence of dextran, the effect of Arg on the chaperone ability of α-crystallin was less than in its absence. Thus, our result suggests that crowding interior media decreases the positive effect of Arg on the chaperone ability of α-crystallin. This is a very important issue, since we are trying to find a mechanism to protect living cells against the toxic effect of protein aggregation.
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Sacchi R, Gardell AM, Chang N, Kültz D. Osmotic regulation and tissue localization of themyo-inositol biosynthesis pathway in tilapia (Oreochromis mossambicus) larvae. ACTA ACUST UNITED AC 2014; 321:457-66. [DOI: 10.1002/jez.1878] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Revised: 05/16/2014] [Accepted: 06/05/2014] [Indexed: 12/23/2022]
Affiliation(s)
- Romina Sacchi
- EcoPhysiological Proteomics Laboratory; Department of Animal Science; University of California; Davis; Davis California
| | - Alison M. Gardell
- EcoPhysiological Proteomics Laboratory; Department of Animal Science; University of California; Davis; Davis California
| | - Nicole Chang
- EcoPhysiological Proteomics Laboratory; Department of Animal Science; University of California; Davis; Davis California
| | - Dietmar Kültz
- EcoPhysiological Proteomics Laboratory; Department of Animal Science; University of California; Davis; Davis California
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In vitro increase of mean corpuscular volume difference (dMCV) as a marker for serum hypertonicity in dogs. Res Vet Sci 2014; 96:442-6. [PMID: 24656345 DOI: 10.1016/j.rvsc.2014.03.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Revised: 01/19/2014] [Accepted: 03/01/2014] [Indexed: 11/21/2022]
Abstract
Spurious increase in erythrocyte mean corpuscular volume (MCV) on automated cell analyzers is a well-characterized lab error in hypertonic patients. A difference between automated and manual MCV (dMCV) greater than 2 fl has been shown to predict hypertonicity in humans. The purpose of this study was to investigate dMCV as a marker for serum hypertonicity in dogs and to examine the relationship between dMCV and three methods of estimating serum tonicity: measured (OsMM), calculated (OsMC), and calculated effective (OsMCE) osmolalities. OsMC, OsMCE, and dMCV were calculated from routine blood values and OsMM was directly measured in 121 dogs. The dMCV of hypertonic dogs was significantly larger than that of normotonic dogs for all three osmolality methods. dMCV predicted hypertonicity as estimated by OsMM better than it predicted hypertonicity as estimated by OsMC and OsMCE. A cutoff of 2.96 fl yielded the best sensitivity (76%) and specificity (71%) for hypertonicity estimated by OsMM.
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Long-term osmotic regulation of amino acid transport systems in mammalian cells. Amino Acids 2013; 11:135-51. [PMID: 24178684 DOI: 10.1007/bf00813857] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/1995] [Accepted: 01/10/1996] [Indexed: 01/05/2023]
Abstract
Mammalian cells accumulate organic osmolytes, either to adapt to permanent osmotic changes or to mediate cell volume increase in cell cycle progression. Amino acids may serve as osmolytes in a great variety of cells. System A, a transport system for neutral amino acids, is induced after hypertonic shock by a mechanism which requires protein synthesis and gene transcription. Indirect evidence supports the view that system A activity increases due to the interaction of pre-existing A carriers with putative activating proteins. The intracellular accumulation of most neutral amino acids after hypertonic shock depends, exclusively, on the increase in system A activity. Long-term activation of system A is dependent on the integrity of cytoskeletal structures, but in a different way depending on whether cells are polarized or not.
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Suppression of Gene Expression by G-Quadruplexes in Open Reading Frames Depends on G-Quadruplex Stability. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201300058] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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Endoh T, Kawasaki Y, Sugimoto N. Suppression of gene expression by G-quadruplexes in open reading frames depends on G-quadruplex stability. Angew Chem Int Ed Engl 2013; 52:5522-6. [PMID: 23589400 DOI: 10.1002/anie.201300058] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2013] [Revised: 03/04/2013] [Indexed: 12/29/2022]
Affiliation(s)
- Tamaki Endoh
- Frontier Institute for Biomolecular Engineering Research, Konan University, 7-1-20 Minatojima-minamimachi, Kobe 650-0047, Japan
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Abstract
Organisms exposed to altered salinity must be able to perceive osmolality change because metabolism has evolved to function optimally at specific intracellular ionic strength and composition. Such osmosensing comprises a complex physiological process involving many elements at organismal and cellular levels of organization. Input from numerous osmosensors is integrated to encode magnitude, direction, and ionic basis of osmolality change. This combinatorial nature of osmosensing is discussed with emphasis on fishes.
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Affiliation(s)
- Dietmar Kültz
- Department of Animal Science, Physiological Genomics Group, University of California, Davis, Davis, California
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Buffer-dependent regulation of aquaporin-1 expression and function in human peritoneal mesothelial cells. Pediatr Nephrol 2012; 27:1165-77. [PMID: 22382466 DOI: 10.1007/s00467-012-2120-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2011] [Revised: 01/17/2012] [Accepted: 01/18/2012] [Indexed: 01/08/2023]
Abstract
BACKGROUND Biocompatible peritoneal dialysis fluids (PDF) are buffered with lactate and/or bicarbonate. We hypothesized that the reduced toxicity of the biocompatible solutions might unmask specific effects of the buffer type on mesothelial cell functions. METHODS Human peritoneal mesothelial cells (HPMC) were incubated with bicarbonate (B-)PDF or lactate-buffered (L-)PDF followed by messenger RNA (mRNA) and protein analysis. Gene silencing was achieved using small interfering RNA (siRNA), functional studies using Transwell culture systems, and monolayer wound-healing assays. RESULTS Incubation with B-PDF increased HPMC migration in the Transwell and monolayer wound-healing assay to 245 ± 99 and 137 ± 11% compared with L-PDF. Gene silencing showed this effect to be entirely dependent on the expression of aquaporin-1 (AQP-1) and independent of AQP-3. Exposure of HPMC to B-PDF increased AQP-1 mRNA and protein abundance to 209 ± 80 and 197 ± 60% of medium control; the effect was pH dependent. L-PDF reduced AQP-1 mRNA. Addition of bicarbonate to L-PDF increased AQP-1 abundance by threefold; mRNA half-life remained unchanged. Immunocytochemistry confirmed opposite changes of AQP-1 cell-membrane abundance with B-PDF and L-PDF. CONCLUSIONS Peritoneal mesothelial AQP-1 abundance and migration capacity is regulated by pH and buffer agents used in PD solutions. In vivo studies are required to delineate the impact with respect to long-term peritoneal membrane integrity and function.
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Pracharova J, Zerzankova L, Stepankova J, Novakova O, Farrer NJ, Sadler PJ, Brabec V, Kasparkova J. Interactions of DNA with a new platinum(IV) azide dipyridine complex activated by UVA and visible light: relationship to toxicity in tumor cells. Chem Res Toxicol 2012; 25:1099-111. [PMID: 22420335 DOI: 10.1021/tx300057y] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The Pt(IV) diazido complex trans,trans,trans-[Pt(N(3))(2)(OH)(2)(pyridine)(2)] (1) is unreactive in the dark but is cytotoxic when photoactivated by UVA and visible light. We have shown that 1 when photoactivated accumulates in tumor cells and binds strongly to nuclear DNA under conditions in which it is toxic to tumor cells. The nature of the DNA adducts, including conformational alterations, induced by photoactivated 1 are distinctly different from those produced in DNA by conventional cisplatin or transplatin. In addition, the observation that major DNA adducts of photoactivated 1 are able to efficiently stall RNA polymerase II more efficiently than cisplatin suggests that transcription inhibition may contribute to the cytotoxicity levels observed for photoactivated 1. Hence, DNA adducts of 1 could trigger a number of downstream cellular effects different from those triggered in cancer cells by DNA adducts of cisplatin. This might lead to the therapeutic effects that could radically improve chemotherapy by platinum complexes. The findings of the present work help to explain the different cytotoxic effects of photoactivated 1 and conventional cisplatin and thereby provide new insights into mechanisms associated with the antitumor effects of platinum complexes photoactivated by UVA and visible light.
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Affiliation(s)
- Jitka Pracharova
- Department of Biophysics, Faculty of Science, Palacky University, 17. Listopadu 12, Olomouc, Czech Republic
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Durazo SA, Kompella UB. Functionalized nanosystems for targeted mitochondrial delivery. Mitochondrion 2011; 12:190-201. [PMID: 22138492 DOI: 10.1016/j.mito.2011.11.001] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2011] [Revised: 11/04/2011] [Accepted: 11/11/2011] [Indexed: 12/19/2022]
Abstract
Mitochondrial dysfunction including oxidative stress and DNA mutations underlies the pathology of various diseases including Alzheimer's disease and diabetes, necessitating the development of mitochondria targeted therapeutic agents. Nanotechnology offers unique tools and materials to target therapeutic agents to mitochondria. As discussed in this paper, a variety of functionalized nanosystems including polymeric and metallic nanoparticles as well as liposomes are more effective than plain drug and non-functionalized nanosystems in delivering therapeutic agents to mitochondria. Although the field is in its infancy, studies to date suggest the superior therapeutic activity of functionalized nanosystems for treating mitochondrial defects.
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Affiliation(s)
- Shelley A Durazo
- Nanomedicine and Drug Delivery Laboratory, Department of Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
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Spitzer J. From water and ions to crowded biomacromolecules: in vivo structuring of a prokaryotic cell. Microbiol Mol Biol Rev 2011; 75:491-506, second page of table of contents. [PMID: 21885682 PMCID: PMC3165543 DOI: 10.1128/mmbr.00010-11] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The interactions and processes which structure prokaryotic cytoplasm (water, ions, metabolites, and biomacromolecules) and ensure the fidelity of the cell cycle are reviewed from a physicochemical perspective. Recent spectroscopic and biological evidence shows that water has no active structuring role in the cytoplasm, an unnecessary notion still entertained in the literature; water acts only as a normal solvent and biochemical reactant. Subcellular structuring arises from localizations and interactions of biomacromolecules and from the growth and modifications of their surfaces by catalytic reactions. Biomacromolecular crowding is a fundamental physicochemical characteristic of cells in vivo. Though some biochemical and physiological effects of crowding (excluded volume effect) have been documented, crowding assays with polyglycols, dextrans, etc., do not properly mimic the compositional variety of biomacromolecules in vivo. In vitro crowding assays are now being designed with proteins, which better reflect biomacromolecular environments in vivo, allowing for hydrophobic bonding and screened electrostatic interactions. I elaborate further the concept of complex vectorial biochemistry, where crowded biomacromolecules structure the cytosol into electrolyte pathways and nanopools that electrochemically "wire" the cell. Noncovalent attractions between biomacromolecules transiently supercrowd biomacromolecules into vectorial, semiconducting multiplexes with a high (35 to 95%)-volume fraction of biomacromolecules; consequently, reservoirs of less crowded cytosol appear in order to maintain the experimental average crowding of ∼25% volume fraction. This nonuniform crowding model allows for fast diffusion of biomacromolecules in the uncrowded cytosolic reservoirs, while the supercrowded vectorial multiplexes conserve the remarkable repeatability of the cell cycle by preventing confusing cross talk of concurrent biochemical reactions.
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Affiliation(s)
- Jan Spitzer
- Mallard Creek Polymers, Inc., 14700 Mallard Creek Road, Charlotte, NC 28262, USA.
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Lane AN. The stability of intramolecular DNA G-quadruplexes compared with other macromolecules. Biochimie 2011; 94:277-86. [PMID: 21854828 DOI: 10.1016/j.biochi.2011.08.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2011] [Accepted: 08/04/2011] [Indexed: 11/19/2022]
Abstract
DNA quadruplexes are often conceived as very stable structures. However, most of the free energy of stabilization derives from specific ion binding via inner sphere coordination of the GO6 of the guanine residues comprising the basic quartet. When compared with other nucleic acid structures such as DNA or RNA duplexes and hairpins, or proteins of the same number of atoms, metal-coordinated intramolecular quadruplexes are found to be of comparable or lower thermodynamic stability under similar solution conditions. Furthermore, intramolecular quadruplexes are actually less stable kinetically, than DNA duplexes or hairpins of the same size. Although the literature is incomplete, it is clear that polyelectrolyte ion effects, the influence of solvation and steric crowding on stability are qualitatively different between intramolecular quadruplexes and DNA duplexes. For example, decreasing water activity destabilizes DNA duplexes, whereas quadruplexes are stabilized. The variety of folded conformations accessible to a single sequence further implies strong sensitivity of the conformational ensemble to the solution conditions, compared with DNA duplexes or small single domain proteins. These considerations may have relevance to the conditions prevailing inside cell nuclei and therefore the structures that potentially might form in vivo.
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Affiliation(s)
- Andrew N Lane
- JG Brown Cancer Center, University of Louisville, 505 S. Hancock St., Louisville, KY 40202, USA.
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Krämer R. Bacterial stimulus perception and signal transduction: response to osmotic stress. CHEM REC 2010; 10:217-29. [PMID: 20607761 DOI: 10.1002/tcr.201000005] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
When exposed to osmotic stress from the environment, bacteria act to maintain cell turgor and hydration by responding both on the level of gene transcription and protein activity. Upon a sudden decrease in external osmolality, internal solutes are released by the action of membrane embedded mechanosensitive channels. In response to an osmotic upshift, the concentration of osmolytes in the cytoplasm is increased both by de novo synthesis and by active uptake. In order to coordinate these processes of osmoregulation, cells are equipped with systems and mechanisms of sensing physical stimuli correlated to changes in the external osmolality (osmosensing), with pathways to transduce these stimuli into useful signals which can be processed in the cell (signal transduction), and mechanisms of regulating proper responses in the cell to recover from the environmental stress and to maintain all necessary physiological functions (osmoregulation). These processes will be described by a number of representative examples, mainly of osmoreactive transport systems with a focus on available data of their molecular mechanism.
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Affiliation(s)
- Reinhard Krämer
- Institute of Biochemistry, University of Cologne, Zülpicher Str. 47, 50674 Cologne, Germany.
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Neurofibromatosis type 1 (NF1) and pheochromocytoma: prevalence, clinical and cardiovascular aspects. Arch Dermatol Res 2010; 303:317-25. [DOI: 10.1007/s00403-010-1090-z] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2010] [Revised: 10/08/2010] [Accepted: 10/13/2010] [Indexed: 11/24/2022]
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Abstract
IMPORTANCE OF THE FIELD Recently-discovered tonicity-dependence of human CYP3A expression in vitro may be a novel mechanism of CYP3A regulation in the intestinal epithelia, which exists in a dynamic osmotic environment influenced by food intake. AREAS COVERED IN THIS REVIEW A combination of focused and comprehensive literature searches to identify any relevant reports using Medline (from 1950 to 7 November 2009) through the OVID system. WHAT THE READER WILL GAIN An update on current knowledge on osmotic environment in the gastrointestinal (GI) tract and its impact on intestinal CYP3A expression and function with special emphasis on the tonicity-sensitive transcription factor nuclear factor of activated T cells 5 (NFAT5). TAKE HOME MESSAGE In vitro hypertonicity of ambient osmotic environment in cultured human cells increases expression of CYP3A through transcriptional enhancement by osmosensitive NFAT5. Although post-prandial osmolality in the GI lumen in vivo is substantially increased, NFAT5 activation has not been reported. Similarly, high-salt diet increases intestinal CYP3A function in humans, but it is not known whether these changes are mediated directly by NFAT5.
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Affiliation(s)
- Andrew I Chuang
- Department of Pharmacology, University of Toronto, Ontario, Canada
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Zerzankova L, Suchankova T, Vrana O, Farrell NP, Brabec V, Kasparkova J. Conformation and recognition of DNA modified by a new antitumor dinuclear PtII complex resistant to decomposition by sulfur nucleophiles. Biochem Pharmacol 2009; 79:112-21. [PMID: 19682435 DOI: 10.1016/j.bcp.2009.08.009] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2009] [Revised: 08/02/2009] [Accepted: 08/05/2009] [Indexed: 11/17/2022]
Abstract
Reported herein is a detailed biochemical and molecular biophysics study of the molecular mechanism of action of antitumor dinuclear Pt(II) complex [{PtCl(DACH)}(2)-mu-Y](4+) [DACH=1,2-diaminocyclohexane, Y=H(2)N(CH(2))(6)NH(2)(CH(2))(2)NH(2)(CH(2))(6)NH(2)] (complex 1). This new, long-chain bifunctional dinuclear Pt(II) complex is resistant to metabolic decomposition by sulfur-containing nucleophiles. The results show that DNA adducts of 1 can largely escape repair and yet inhibit very effectively transcription so that they should persist longer than those of conventional cisplatin. Hence, they could trigger a number of downstream cellular effects different from those triggered in cancer cells by DNA adducts of cisplatin. This might lead to the therapeutic effects that could radically improve chemotherapy by platinum complexes. In addition, the findings of the present work make new insights into mechanisms associated with antitumor effects of dinuclear/trinuclear Pt(II) complexes possible.
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Affiliation(s)
- Lenka Zerzankova
- Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i., Kralovopolska 135, CZ-61265 Brno, Czech Republic
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Huang L, Dong L, Chen Y, Qi H, Xiao D. Effects of Sinusoidal Magnetic Field Observed on Cell Proliferation, Ion Concentration, and Osmolarity in Two Human Cancer Cell Lines. Electromagn Biol Med 2009; 25:113-26. [PMID: 16771300 DOI: 10.1080/15368370600719067] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Low frequency magnetic fields have previously been shown to affect cell functions. In this article, the effects of 20 mT, 50 Hz sinusoidal magnetic field on cell proliferation, ion concentration, and osmolarity in two human cancer cell lines (HL-60 and SK-Hep-1) were investigated. Inhibition of cell growth was observed. On the other hand, the exposure also increased the Na+, K+ ion concentration and osmolarity in cell supernatant compared to the control group. To our knowledge, this is the first study on cancer cells where magnetic fields affect osmolarity in cell supernatant. In addition, a model of cells exposed to the oscillating magnetic field is described as well as the characteristics of ions in and out of cells. The experimental data appears to be consistent with the theoretical analysis. The results are also discussed in terms of the relationships among cell growth, ion concentration, and osmolarity. Magnetic field inhibitions of cell growth in vitro may relate to changes in cell ion concentration and osmolarity.
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Affiliation(s)
- Lingzhen Huang
- Department of Electrical Engineering, Shanghai Jiaotong University, Shanghai, China
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Unni US, Ramakrishnan G, Raj T, Kishore RP, Thomas T, Vaz M, Kurpad AV. Muscle mass and functional correlates of insulin sensitivity in lean young Indian men. Eur J Clin Nutr 2009; 63:1206-12. [DOI: 10.1038/ejcn.2009.32] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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Foster C, Amado EM, Souza MM, Freire CA. Do osmoregulators have lower capacity of muscle water regulation than osmoconformers? A study on decapod crustaceans. ACTA ACUST UNITED AC 2009; 313:80-94. [DOI: 10.1002/jez.575] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Espelt MV, Alleva K, Amodeo G, Krumschnabel G, Rossi RC, Schwarzbaum PJ. Volumetric response of vertebrate hepatocytes challenged by osmotic gradients: a theoretical approach. Comp Biochem Physiol B Biochem Mol Biol 2008; 150:103-11. [PMID: 18329306 DOI: 10.1016/j.cbpb.2008.02.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2007] [Revised: 02/01/2008] [Accepted: 02/02/2008] [Indexed: 10/22/2022]
Abstract
In this study we use a theoretical approach to study the volumetric response of goldfish hepatocytes challenged by osmotic gradients and compared it with that of hepatocytes from another teleost (the trout) and a mammal (the rat). Particular focus was given to the multiple non-linear interactions of transport systems enabling hypotonically challenged cells to trigger a compensatory response known as volume regulatory decrease or RVD. For this purpose we employed a mathematical model which describes the rates of change of the intracellular concentrations of main diffusible ions, of the cell volume, and of the membrane potential. The model was fitted to experimental data on the kinetics of volume change of hepatocytes challenged by anisotonic media. In trout and rat hepatocytes, experimental results had shown that hypotonic cell swelling was followed by RVD, whereas goldfish cells swelled with no concomitant RVD (M.V. Espelt et al., 2003, J. Exp. Biol. 206, 513-522). A comparison between data predicted by the model and that obtained experimentally suggests that in trout and rat hepatocytes hypotonicity activates a sensor element and this, in turn, activates an otherwise silent efflux of KCl - whose kinetics could be successfully predicted - thereby leading to volume down-regulation. In contrast, with regard to the absence of RVD in goldfish hepatocytes the model proposed suggests that either a sensor element triggering RVD is absent or that the effector mechanism (the loss of KCl) remains inactive under the conditions employed. In line with this, we recently found that extracellular nucleotides may be required to induce RVD in these cells, indicating that our model could indeed lead to useful predictions.
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Affiliation(s)
- M V Espelt
- Instituto de Química y Fisicoquímica Biológicas (Facultad de Farmacia y Bioquímica), Universidad de Buenos Aires, C1113AAD Buenos Aires, Argentina
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Chopra S, Dooling RM, Horner CG, Howell EE. A balancing act between net uptake of water during dihydrofolate binding and net release of water upon NADPH binding in R67 dihydrofolate reductase. J Biol Chem 2007; 283:4690-8. [PMID: 18086667 DOI: 10.1074/jbc.m709443200] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
R67 dihydrofolate reductase (DHFR) catalyzes the reduction of dihydrofolate (DHF) to tetrahydrofolate using NADPH as a cofactor. This enzyme is a homotetramer possessing 222 symmetry, and a single active site pore traverses the length of the protein. A promiscuous binding surface can accommodate either DHF or NADPH, thus two nonproductive complexes can form (2NADPH or 2DHF) as well as a productive complex (NADPH.DHF). The role of water in binding was monitored using a number of different osmolytes. From isothermal titration calorimetry (ITC) studies, binding of NADPH is accompanied by the net release of 38 water molecules. In contrast, from both steady state kinetics and ITC studies, binding of DHF is accompanied by the net uptake of water. Although different osmolytes have similar effects on NADPH binding, variable results are observed when DHF binding is probed. Sensitivity to water activity can also be probed by an in vivo selection using the antibacterial drug, trimethoprim, where the water content of the media is decreased by increasing concentrations of sorbitol. The ability of wild type and mutant clones of R67 DHFR to allow host Escherichia coli to grow in the presence of trimethoprim plus added sorbitol parallels the catalytic efficiency of the DHFR clones, indicating water content strongly correlates with the in vivo function of R67 DHFR.
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Affiliation(s)
- Shaileja Chopra
- Department of Biochemistry, Cellular, and Molecular Biology, University of Tennessee, Knoxville, Tennessee 37996-0840, USA
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Chebotareva NA. Effect of molecular crowding on the enzymes of glycogenolysis. BIOCHEMISTRY (MOSCOW) 2007; 72:1478-90. [DOI: 10.1134/s0006297907130056] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Abstract
Cells in the renal inner medulla are normally exposed to extraordinarily high levels of NaCl and urea. The osmotic stress causes numerous perturbations because of the hypertonic effect of high NaCl and the direct denaturation of cellular macromolecules by high urea. High NaCl and urea elevate reactive oxygen species, cause cytoskeletal rearrangement, inhibit DNA replication and transcription, inhibit translation, depolarize mitochondria, and damage DNA and proteins. Nevertheless, cells can accommodate by changes that include accumulation of organic osmolytes and increased expression of heat shock proteins. Failure to accommodate results in cell death by apoptosis. Although the adapted cells survive and function, many of the original perturbations persist, and even contribute to signaling the adaptive responses. This review addresses both the perturbing effects of high NaCl and urea and the adaptive responses. We speculate on the sensors of osmolality and document the multiple pathways that signal activation of the transcription factor TonEBP/OREBP, which directs many aspects of adaptation. The facts that numerous cellular functions are altered by hyperosmolality and remain so, even after adaptation, indicate that both the effects of hyperosmolality and adaptation to it involve profound alterations of the state of the cells.
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Hoffman JF. Further musings on some red blood cell problems for perspicacious physiologists. Blood Cells Mol Dis 2007; 39:56-62. [PMID: 17434767 DOI: 10.1016/j.bcmd.2007.03.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2007] [Accepted: 03/06/2007] [Indexed: 11/20/2022]
Affiliation(s)
- Joseph F Hoffman
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520-8026, USA.
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Simonin H, Beney L, Gervais P. Cell death induced by mild physical perturbations could be related to transient plasma membrane modifications. J Membr Biol 2007; 216:37-47. [PMID: 17568970 DOI: 10.1007/s00232-007-9027-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2006] [Revised: 02/15/2007] [Accepted: 04/19/2007] [Indexed: 11/30/2022]
Abstract
An understanding of membrane destabilization induced by osmotic treatments is important to better control cell survival during biotechnological processes. The effects on the membranes of the yeast Saccharomyces cerevisiae of perturbations similar in intensity (same amount of energy) but differing in the source type (heat, compression and osmotic gradient) were investigated. The anisotropy of the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene was measured before and after each treatment to assess the reversibility of the membrane changes related to each treatment. Except for heat shock at 75 degrees C, changes in membrane fluidity were reversible after the return to initial conditions, showing that two kinds of physical stress can be distinguished regarding the reversibility of membrane changes: high and mild energy stresses. With the application of osmotic gradients, anisotropy was assessed during treatment with five osmotic pressure levels from 30.7 to 95.4 MPa with two different yeast strains and related to the rate of cell death caused by each stress. The exposure of cells to increasing osmotic pressures involved a progressive lowering of membrane anisotropy during lethal perturbations. Osmotic stresses associated with reversible fluidity changes of increasing intensity in the membrane led to proportional death rates and time-dependent cell death of increasing rapidity during the application of the stress. Finally, a hypothesis relating the extent of membrane structural changes to the kinetic of cell death is proposed.
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Affiliation(s)
- Hélène Simonin
- Laboratoire de Génie des Procédés Alimentaires et Biotechnologiques ENSBANA (Ecole Nationale Supérieure de Biologie Appliquée à la Nutrition et l'Alimentation), 1 Esplanade Erasme, 21000 Dijon, France
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Energetics of the protein-DNA-water interaction. BMC STRUCTURAL BIOLOGY 2007; 7:4. [PMID: 17214883 PMCID: PMC1781455 DOI: 10.1186/1472-6807-7-4] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/14/2006] [Accepted: 01/10/2007] [Indexed: 11/30/2022]
Abstract
Background To understand the energetics of the interaction between protein and DNA we analyzed 39 crystallographically characterized complexes with the HINT (Hydropathic INTeractions) computational model. HINT is an empirical free energy force field based on solvent partitioning of small molecules between water and 1-octanol. Our previous studies on protein-ligand complexes demonstrated that free energy predictions were significantly improved by taking into account the energetic contribution of water molecules that form at least one hydrogen bond with each interacting species. Results An initial correlation between the calculated HINT scores and the experimentally determined binding free energies in the protein-DNA system exhibited a relatively poor r2 of 0.21 and standard error of ± 1.71 kcal mol-1. However, the inclusion of 261 waters that bridge protein and DNA improved the HINT score-free energy correlation to an r2 of 0.56 and standard error of ± 1.28 kcal mol-1. Analysis of the water role and energy contributions indicate that 46% of the bridging waters act as linkers between amino acids and nucleotide bases at the protein-DNA interface, while the remaining 54% are largely involved in screening unfavorable electrostatic contacts. Conclusion This study quantifies the key energetic role of bridging waters in protein-DNA associations. In addition, the relevant role of hydrophobic interactions and entropy in driving protein-DNA association is indicated by analyses of interaction character showing that, together, the favorable polar and unfavorable polar/hydrophobic-polar interactions (i.e., desolvation) mostly cancel.
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Konopka MC, Shkel IA, Cayley S, Record MT, Weisshaar JC. Crowding and confinement effects on protein diffusion in vivo. J Bacteriol 2006; 188:6115-23. [PMID: 16923878 PMCID: PMC1595386 DOI: 10.1128/jb.01982-05] [Citation(s) in RCA: 153] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The first in vivo measurements of a protein diffusion coefficient versus cytoplasmic biopolymer volume fraction are presented. Fluorescence recovery after photobleaching yields the effective diffusion coefficient on a 1-mum-length scale of green fluorescent protein within the cytoplasm of Escherichia coli grown in rich medium. Resuspension into hyperosmotic buffer lacking K+ and nutrients extracts cytoplasmic water, systematically increasing mean biopolymer volume fraction, <phi>, and thus the severity of possible crowding, binding, and confinement effects. For resuspension in isosmotic buffer (osmotic upshift, or Delta, of 0), the mean diffusion coefficient, <D>, in cytoplasm (6.1 +/- 2.4 microm2 s(-1)) is only 0.07 of the in vitro value (87 microm2 s(-1)); the relative dispersion among cells, sigmaD/<D> (standard deviation, sigma(D), relative to the mean), is 0.39. Both <D> and sigmaD/<D> remain remarkably constant over the range of Delta values of 0 to 0.28 osmolal. For a Delta value of > or =0.28 osmolal, formation of visible plasmolysis spaces (VPSs) coincides with the onset of a rapid decrease in <D> by a factor of 380 over the range of Delta values of 0.28 to 0.70 osmolal and a substantial increase in sigmaD/<D>. Individual values of D vary by a factor of 9 x 10(4) but correlate well with f(VPS), the fractional change in cytoplasmic volume on VPS formation. The analysis reveals two levels of dispersion in D among cells: moderate dispersion at low Delta values for cells lacking a VPS, perhaps related to variation in phi or biopolymer organization during the cell cycle, and stronger dispersion at high Delta values related to variation in f(VPS). Crowding effects alone cannot explain the data, nor do these data alone distinguish crowding from possible binding or confinement effects within a cytoplasmic meshwork.
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Affiliation(s)
- Michael C Konopka
- Department of Chemistry, University of Wisconsin-Madison, Madison, 1101 University Avenue, WI 53706, USA
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Acerenza L, Graña M. On the origins of a crowded cytoplasm. J Mol Evol 2006; 63:583-90. [PMID: 17009126 DOI: 10.1007/s00239-006-0018-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2006] [Accepted: 06/26/2006] [Indexed: 10/24/2022]
Abstract
Contemporary cells show a highly crowded macromolecular content, the processes which originated this state being largely unknown. We propose that a driving force leading to the crowded cellular state could be the increase in growth rate produced by an enhanced cytoplasmic protein concentration. Briefly, in a diluted scenario, an increase in protein concentration has two opposing effects on growth rate. The favorable effect is the increase in the activity per unit volume of the component proteins and the disadvantageous effect is the concomitant increase in the protein mass per unit volume which has to be produced. In this work we show that the first effect is quantitatively more important, resulting in an overall increase in growth rate. This result was obtained with a model of E. coli and using nonmechanistic physiological arguments. The proposed driving force operates even at low protein concentrations, where the nonspecific interactions of macromolecular crowding are not significant, and could be as ancient as the first protocells. Experimental measurement of this cytoplasmic protein concentration effect in present organisms is hindered by the prevailing nonspecific interactions, product of long-term evolution. However, chemical/biochemical systems, built up to mimic properties of living cells, could be an adequate tool to test this effect.
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Affiliation(s)
- Luis Acerenza
- Systems Biology Laboratory, Faculty of Sciences, University of Republic, Montevideo, Uruguay.
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Wheeler JM, Thomas JH. Identification of a novel gene family involved in osmotic stress response in Caenorhabditis elegans. Genetics 2006; 174:1327-36. [PMID: 16980399 PMCID: PMC1667073 DOI: 10.1534/genetics.106.059089] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Organisms exposed to the damaging effects of high osmolarity accumulate solutes to increase cytoplasmic osmolarity. Yeast accumulates glycerol in response to osmotic stress, activated primarily by MAP kinase Hog1 signaling. A pathway regulated by protein kinase C (PKC1) also responds to changes in osmolarity and cell wall integrity. C. elegans accumulates glycerol when exposed to high osmolarity, but the molecular pathways responsible for this are not well understood. We report the identification of two genes, osm-7 and osm-11, which are related members of a novel gene family. Mutations in either gene lead to high internal levels of glycerol and cause an osmotic resistance phenotype (Osr). These mutants also have an altered defecation rhythm (Dec). Mutations in cuticle collagen genes dpy-2, dpy-7, and dpy-10 cause a similar Osr Dec phenotype. osm-7 is expressed in the hypodermis and may be secreted. We hypothesize that osm-7 and osm-11 interact with the cuticle, and disruption of the cuticle causes activation of signaling pathways that increase glycerol production. The phenotypes of osm-7 are not suppressed by mutations in MAP kinase or PKC pathways, suggesting that C. elegans uses signaling pathways different from yeast to mount a response to osmotic stress.
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Affiliation(s)
- Jeanna M Wheeler
- Department of Genome Sciences, University of Washington, Seattle, Washington 98195, USA
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Svedruzić ZM, Spivey HO. Interaction between mammalian glyceraldehyde-3-phosphate dehydrogenase and L-lactate dehydrogenase from heart and muscle. Proteins 2006; 63:501-11. [PMID: 16444750 DOI: 10.1002/prot.20862] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The exceptionally high protein concentration in living cells can favor functional protein-protein interactions that can be difficult to detect with purified proteins. In this study we describe specific interactions between mammalian D-glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and L-lactate dehydrogenase (LDH) isozymes from heart and muscle. We use poly(ethylene-glycol) (PEG)-induced coprecipitation and native agarose electrophoresis as two independent methods uniquely suited to mimic some of the conditions that can favor protein-protein interaction in living cells. We found that GAPDH interacts with heart or muscle isozymes of LDH with approximately one-to-one stoichiometry. The interaction is specific; GAPDH shows interaction with two LDH isozymes that have very different net charge and solubility in PEG solution, while no interaction is observed with GAPDH from other species, other NAD(H) dehydrogenases, or other proteins that have very similar net charge and molecular mass. Analytical ultracentrifugation showed that the LDH and GAPDH complex is insoluble in PEG solution. The interaction is abolished by saturation with NADH, but not by saturation with NAD(+) in correlation with GAPDH solubility in PEG solution. The crystal structures show that GAPDH and LDH isozymes share complementary size, shape, and electric potential surrounding the active sites. The presented results suggest that GAPDH and LDH have a functional interaction that can affect NAD(+)/NADH metabolism and glycolysis in living cells.
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Affiliation(s)
- Zeljko M Svedruzić
- Department of Biochemistry and Molecular Biology, 246 B Noble Research Center, Oklahoma State University, Stillwater, Oklahoma 74078, USA.
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