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Khandwala CB, Sarkar P, Schmidt HB, Ma M, Kinnebrew M, Pusapati GV, Patel BB, Tillo D, Lebensohn AM, Rohatgi R. Direct ionic stress sensing and mitigation by the transcription factor NFAT5. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.23.559074. [PMID: 37886503 PMCID: PMC10602047 DOI: 10.1101/2023.09.23.559074] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/28/2023]
Abstract
Homeostatic control of intracellular ionic strength is essential for protein, organelle and genome function, yet mechanisms that sense and enable adaptation to ionic stress remain poorly understood in animals. We find that the transcription factor NFAT5 directly senses solution ionic strength using a C-terminal intrinsically disordered region. Both in intact cells and in a purified system, NFAT5 forms dynamic, reversible biomolecular condensates in response to increasing ionic strength. This self-associative property, conserved from insects to mammals, allows NFAT5 to accumulate in the nucleus and activate genes that restore cellular ion content. Mutations that reduce condensation or those that promote aggregation both reduce NFAT5 activity, highlighting the importance of optimally tuned associative interactions. Remarkably, human NFAT5 alone is sufficient to reconstitute a mammalian transcriptional response to ionic or hypertonic stress in yeast. Thus NFAT5 is both the sensor and effector of a cell-autonomous ionic stress response pathway in animal cells.
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Affiliation(s)
- Chandni B. Khandwala
- Departments of Biochemistry and Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Parijat Sarkar
- Departments of Biochemistry and Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - H. Broder Schmidt
- Departments of Biochemistry and Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Mengxiao Ma
- Departments of Biochemistry and Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Maia Kinnebrew
- Departments of Biochemistry and Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Ganesh V. Pusapati
- Departments of Biochemistry and Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Bhaven B. Patel
- Departments of Biochemistry and Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Desiree Tillo
- Center for Cancer Research Genomics Core, National Cancer Institute, National Institutes of Health, NIH, Building 37, RM 2056B, Bethesda, MD, 20892, USA
| | - Andres M. Lebensohn
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, NIH, Building 37, RM 2056B, Bethesda, MD, 20892, USA
| | - Rajat Rohatgi
- Departments of Biochemistry and Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
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Orlov SN, Shiyan A, Boudreault F, Ponomarchuk O, Grygorczyk R. Search for Upstream Cell Volume Sensors: The Role of Plasma Membrane and Cytoplasmic Hydrogel. CURRENT TOPICS IN MEMBRANES 2018; 81:53-82. [PMID: 30243440 DOI: 10.1016/bs.ctm.2018.07.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
The plasma membrane plays a prominent role in the regulation of cell volume by mediating selective transport of extra- and intracellular osmolytes. Recent studies show that upstream sensors of cell volume changes are mainly located within the cytoplasm that displays properties of a hydrogel and not in the plasma membrane. Cell volume changes occurring in anisosmotic medium as well as in isosmotic environment affect properties of cytoplasmic hydrogel that, in turn, trigger rapid regulatory volume increase and decrease (RVI and RVD). The downstream signaling pathways include reorganization of 2D cytoskeleton and altered composition of polyphosphoinositides located on the inner surface of the plasma membrane. In addition to its action on physico-chemical properties of cytoplasmic hydrogel, cell volume changes in anisosmotic conditions affect the ionic strength of the cytoplasm and the [Na+]i/[K+]i ratio. Elevated intracellular ionic strength evoked by long term exposure of cells to hypertonic environment resulted in the activation of TonEBP and augmented expression of genes controlling intracellular organic osmolyte levels. The role of Na+i/K+i -sensitive, Ca2+i -mediated and Ca2+i-independent mechanisms of excitation-transcription coupling in cell volume-adjustment remains unknown.
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Affiliation(s)
- Sergei N Orlov
- Faculty of Biology, M.V. Lomonosov Moscow State University, Moscow, Russia; Siberian State Medical University, Tomsk, Russia; National Research Tomsk State University, Tomsk, Russia
| | - Aleksandra Shiyan
- Faculty of Biology, M.V. Lomonosov Moscow State University, Moscow, Russia
| | - Francis Boudreault
- Centre de recherche, Centre hospitalier de l'Université de Montréal (CRCHUM), Montreal, QC, Canada
| | - Olga Ponomarchuk
- Faculty of Biology, M.V. Lomonosov Moscow State University, Moscow, Russia; Centre de recherche, Centre hospitalier de l'Université de Montréal (CRCHUM), Montreal, QC, Canada
| | - Ryszard Grygorczyk
- Centre de recherche, Centre hospitalier de l'Université de Montréal (CRCHUM), Montreal, QC, Canada; Department of Medicine, Faculty of Medicine, University of Montreal, Montreal, QC, Canada
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Zhang Q, Bhattacharya S, Pi J, Clewell RA, Carmichael PL, Andersen ME. Adaptive Posttranslational Control in Cellular Stress Response Pathways and Its Relationship to Toxicity Testing and Safety Assessment. Toxicol Sci 2016; 147:302-16. [PMID: 26408567 DOI: 10.1093/toxsci/kfv130] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Although transcriptional induction of stress genes constitutes a major cellular defense program against a variety of stressors, posttranslational control directly regulating the activities of preexisting stress proteins provides a faster-acting alternative response. We propose that posttranslational control is a general adaptive mechanism operating in many stress pathways. Here with the aid of computational models, we first show that posttranslational control fulfills two roles: (1) handling small, transient stresses quickly and (2) stabilizing the negative feedback transcriptional network. We then review the posttranslational control pathways for major stress responses-oxidative stress, metal stress, hyperosmotic stress, DNA damage, heat shock, and hypoxia. Posttranslational regulation of stress protein activities occurs by reversible covalent modifications, allosteric or non-allosteric enzymatic regulations, and physically induced protein structural changes. Acting in feedback or feedforward networks, posttranslational control may establish a threshold level of cellular stress. Sub-threshold stresses are handled adequately by posttranslational control without invoking gene transcription. With supra-threshold stress levels, cellular homeostasis cannot be maintained and transcriptional induction of stress genes and other gene programs, eg, those regulating cell metabolism, proliferation, and apoptosis, takes place. The loss of homeostasis with consequent changes in cellular function may lead to adverse cellular outcomes. Overall, posttranslational and transcriptional control pathways constitute a stratified cellular defense system, handling stresses coherently across time and intensity. As cell-based assays become a focus for chemical testing anchored on toxicity pathways, examination of proteomic and metabolomic changes as a result of posttranslational control occurring in the absence of transcriptomic alterations deserves more attention.
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Affiliation(s)
- Qiang Zhang
- *Institute for Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, North Carolina 27709; School of Public Health, China Medical University, Shenyang, China; and Unilever, Safety and Environmental Assurance Centre, Colworth Science Park, Sharnbrook, Bedfordshire, UK
| | - Sudin Bhattacharya
- *Institute for Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, North Carolina 27709; School of Public Health, China Medical University, Shenyang, China; and Unilever, Safety and Environmental Assurance Centre, Colworth Science Park, Sharnbrook, Bedfordshire, UK
| | - Jingbo Pi
- *Institute for Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, North Carolina 27709; School of Public Health, China Medical University, Shenyang, China; and Unilever, Safety and Environmental Assurance Centre, Colworth Science Park, Sharnbrook, Bedfordshire, UK
| | - Rebecca A Clewell
- *Institute for Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, North Carolina 27709; School of Public Health, China Medical University, Shenyang, China; and Unilever, Safety and Environmental Assurance Centre, Colworth Science Park, Sharnbrook, Bedfordshire, UK
| | - Paul L Carmichael
- *Institute for Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, North Carolina 27709; School of Public Health, China Medical University, Shenyang, China; and Unilever, Safety and Environmental Assurance Centre, Colworth Science Park, Sharnbrook, Bedfordshire, UK
| | - Melvin E Andersen
- *Institute for Chemical Safety Sciences, The Hamner Institutes for Health Sciences, Research Triangle Park, North Carolina 27709; School of Public Health, China Medical University, Shenyang, China; and Unilever, Safety and Environmental Assurance Centre, Colworth Science Park, Sharnbrook, Bedfordshire, UK
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Bounedjah O, Hamon L, Savarin P, Desforges B, Curmi PA, Pastré D. Macromolecular crowding regulates assembly of mRNA stress granules after osmotic stress: new role for compatible osmolytes. J Biol Chem 2011; 287:2446-58. [PMID: 22147700 DOI: 10.1074/jbc.m111.292748] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The massive uptake of compatible osmolytes such as betaine, taurine, and myo-inositol is a protective response shared by all eukaryotes exposed to hypertonic stress. Their accumulation results mostly from the expression of specific transporters triggered by the transcriptional factor NFAT5/TonEBP. This allows the recovery of the cell volume without increasing intracellular ionic strength. In this study we consider the assembly and dissociation of mRNA stress granules (SGs) in hypertonic-stressed cells and the role of compatible osmolytes. In agreement with in vitro results obtained on isolated mRNAs, both macromolecular crowding and a high ionic strength favor the assembly of SGs in normal rat kidney epithelial cells. However, after hours of constant hypertonicity, the slow accumulation in the cytoplasm of compatible osmolytes via specific transporters both reduces macromolecular crowding and ionic strength, thus leading to the progressive dissociation of SGs. In line with this, when cells are exposed to hypertonicity to accumulate a large amount of compatible osmolytes, the formation of SGs is severely impaired, and cells increase their chances of survival to another hypertonic episode. Altogether, these results indicate that the impact of compatible osmolytes on the mRNA-associated machineries and especially that associated with SGs may play an important role in cell resistance and adaption to hyperosmolarity in many tissues like kidney and liver.
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Affiliation(s)
- Ouissame Bounedjah
- Laboratoire Structure-Activité des Biomolécules Normales et Pathologiques, INSERM U829 and Université Evry-Val d'Essonne, Evry 91025, France
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Pedersen SF, Kapus A, Hoffmann EK. Osmosensory mechanisms in cellular and systemic volume regulation. J Am Soc Nephrol 2011; 22:1587-97. [PMID: 21852585 DOI: 10.1681/asn.2010121284] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Perturbations of cellular and systemic osmolarity severely challenge the function of all organisms and are consequently regulated very tightly. Here we outline current evidence on how cells sense volume perturbations, with particular focus on mechanisms relevant to the kidneys and to extracellular osmolarity and whole body volume homeostasis. There are a variety of molecular signals that respond to perturbations in cell volume and osmosensors or volume sensors responding to these signals. The early signals of volume perturbation include integrins, the cytoskeleton, receptor tyrosine kinases, and transient receptor potential channels. We also present current evidence on the localization and function of central and peripheral systemic osmosensors and conclude with a brief look at the still limited evidence on pathophysiological conditions associated with deranged sensing of cell volume.
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Affiliation(s)
- Stine Falsig Pedersen
- Department of Biology, University of Copenhagen, Universitetsparken 13, DK-2100, Copenhagen, Denmark.
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Hoffmann EK, Lambert IH, Pedersen SF. Physiology of cell volume regulation in vertebrates. Physiol Rev 2009; 89:193-277. [PMID: 19126758 DOI: 10.1152/physrev.00037.2007] [Citation(s) in RCA: 1023] [Impact Index Per Article: 68.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The ability to control cell volume is pivotal for cell function. Cell volume perturbation elicits a wide array of signaling events, leading to protective (e.g., cytoskeletal rearrangement) and adaptive (e.g., altered expression of osmolyte transporters and heat shock proteins) measures and, in most cases, activation of volume regulatory osmolyte transport. After acute swelling, cell volume is regulated by the process of regulatory volume decrease (RVD), which involves the activation of KCl cotransport and of channels mediating K(+), Cl(-), and taurine efflux. Conversely, after acute shrinkage, cell volume is regulated by the process of regulatory volume increase (RVI), which is mediated primarily by Na(+)/H(+) exchange, Na(+)-K(+)-2Cl(-) cotransport, and Na(+) channels. Here, we review in detail the current knowledge regarding the molecular identity of these transport pathways and their regulation by, e.g., membrane deformation, ionic strength, Ca(2+), protein kinases and phosphatases, cytoskeletal elements, GTP binding proteins, lipid mediators, and reactive oxygen species, upon changes in cell volume. We also discuss the nature of the upstream elements in volume sensing in vertebrate organisms. Importantly, cell volume impacts on a wide array of physiological processes, including transepithelial transport; cell migration, proliferation, and death; and changes in cell volume function as specific signals regulating these processes. A discussion of this issue concludes the review.
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Affiliation(s)
- Else K Hoffmann
- Department of Biology, University of Copenhagen, Copenhagen, Denmark.
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