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Pavesic MW, Gale AN, Nickels TJ, Harrington AA, Bussey M, Cunningham KW. Calcineurin-dependent contributions to fitness in the opportunistic pathogen Candida glabrata. mSphere 2024; 9:e0055423. [PMID: 38171022 PMCID: PMC10826367 DOI: 10.1128/msphere.00554-23] [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] [Received: 09/22/2023] [Accepted: 11/19/2023] [Indexed: 01/05/2024] Open
Abstract
The protein phosphatase calcineurin is vital for the virulence of the opportunistic fungal pathogen Candida glabrata. The host-induced stresses that activate calcineurin signaling are unknown, as are the targets of calcineurin relevant to virulence. To potentially shed light on these processes, millions of transposon insertion mutants throughout the genome of C. glabrata were profiled en masse for fitness defects in the presence of FK506, a specific inhibitor of calcineurin. Eighty-seven specific gene deficiencies depended on calcineurin signaling for full viability in vitro both in wild-type and pdr1∆ null strains lacking pleiotropic drug resistance. Three genes involved in cell wall biosynthesis (FKS1, DCW1, FLC1) possess co-essential paralogs whose expression depended on calcineurin and Crz1 in response to micafungin, a clinical antifungal that interferes with cell wall biogenesis. Interestingly, 80% of the FK506-sensitive mutants were deficient in different aspects of vesicular trafficking, such as endocytosis, exocytosis, sorting, and biogenesis of secretory proteins in the endoplasmic reticulum (ER). In response to the experimental antifungal manogepix that blocks GPI-anchor biosynthesis in the ER, calcineurin signaling increased and strongly prevented cell death independent of Crz1, one of its major targets. Comparisons between manogepix, micafungin, and the ER-stressing tunicamycin reveal a correlation between the degree of calcineurin signaling and the degree of cell survival. These findings suggest that calcineurin plays major roles in mitigating stresses of vesicular trafficking. Such stresses may arise during host infection and in response to antifungal therapies.IMPORTANCECalcineurin plays critical roles in the virulence of most pathogenic fungi. This study sheds light on those roles in the opportunistic pathogen Candida glabrata using a genome-wide analysis in vitro. The findings could lead to antifungal developments that also avoid immunosuppression.
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Affiliation(s)
- Matthew W. Pavesic
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Andrew N. Gale
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Timothy J. Nickels
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, USA
| | | | - Maya Bussey
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Kyle W. Cunningham
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, USA
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2
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Nenadic A, Zaman MF, Johansen J, Volpiana MW, Beh CT. Increased Phospholipid Flux Bypasses Overlapping Essential Requirements for the Yeast Sac1p Phosphoinositide Phosphatase and ER-PM Membrane Contact Sites. J Biol Chem 2023; 299:105092. [PMID: 37507017 PMCID: PMC10470028 DOI: 10.1016/j.jbc.2023.105092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2022] [Revised: 07/13/2023] [Accepted: 07/17/2023] [Indexed: 07/30/2023] Open
Abstract
In budding yeast cells, much of the inner surface of the plasma membrane (PM) is covered with the endoplasmic reticulum (ER). This association is mediated by seven ER membrane proteins that confer cortical ER-PM association at membrane contact sites (MCSs). Several of these membrane "tether" proteins are known to physically interact with the phosphoinositide phosphatase Sac1p. However, it is unclear how or if these interactions are necessary for their interdependent functions. We find that SAC1 inactivation in cells lacking the homologous synaptojanin-like genes INP52 and INP53 results in a significant increase in cortical ER-PM MCSs. We show in sac1Δ, sac1tsinp52Δ inp53Δ, or Δ-super-tether (Δ-s-tether) cells lacking all seven ER-PM tethering genes that phospholipid biosynthesis is disrupted and phosphoinositide distribution is altered. Furthermore, SAC1 deletion in Δ-s-tether cells results in lethality, indicating a functional overlap between SAC1 and ER-PM tethering genes. Transcriptomic profiling indicates that SAC1 inactivation in either Δ-s-tether or inp52Δ inp53Δ cells induces an ER membrane stress response and elicits phosphoinositide-dependent changes in expression of autophagy genes. In addition, by isolating high-copy suppressors that rescue sac1Δ Δ-s-tether lethality, we find that key phospholipid biosynthesis genes bypass the overlapping function of SAC1 and ER-PM tethers and that overexpression of the phosphatidylserine/phosphatidylinositol-4-phosphate transfer protein Osh6 also provides limited suppression. Combined with lipidomic analysis and determinations of intracellular phospholipid distributions, these results suggest that Sac1p and ER phospholipid flux controls lipid distribution to drive Osh6p-dependent phosphatidylserine/phosphatidylinositol-4-phosphate counter-exchange at ER-PM MCSs.
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Affiliation(s)
- Aleksa Nenadic
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Mohammad F Zaman
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Jesper Johansen
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Matthew W Volpiana
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Christopher T Beh
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada; Centre for Cell Biology, Development, and Disease, Simon Fraser University, Burnaby, British Columbia, Canada.
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3
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Chawla S, Ahmadpour D, Schneider KL, Kumar N, Fischbach A, Molin M, Nystrom T. Calcineurin stimulation by Cnb1p overproduction mitigates protein aggregation and α-synuclein toxicity in a yeast model of synucleinopathy. Cell Commun Signal 2023; 21:220. [PMID: 37620860 PMCID: PMC10464345 DOI: 10.1186/s12964-023-01242-w] [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] [Received: 05/06/2023] [Accepted: 07/22/2023] [Indexed: 08/26/2023] Open
Abstract
The calcium-responsive phosphatase, calcineurin, senses changes in Ca2+ concentrations in a calmodulin-dependent manner. Here we report that under non-stress conditions, inactivation of calcineurin signaling or deleting the calcineurin-dependent transcription factor CRZ1 triggered the formation of chaperone Hsp100p (Hsp104p)-associated protein aggregates in Saccharomyces cerevisiae. Furthermore, calcineurin inactivation aggravated α-Synuclein-related cytotoxicity. Conversely, elevated production of the calcineurin activator, Cnb1p, suppressed protein aggregation and cytotoxicity associated with the familial Parkinson's disease-related mutant α-Synuclein A53T in a partly CRZ1-dependent manner. Activation of calcineurin boosted normal localization of both wild type and mutant α-synuclein to the plasma membrane, an intervention previously shown to mitigate α-synuclein toxicity in Parkinson's disease models. The findings demonstrate that calcineurin signaling, and Ca2+ influx to the vacuole, limit protein quality control in non-stressed cells and may have implications for elucidating to which extent aberrant calcineurin signaling contributes to the progression of Parkinson's disease(s) and other synucleinopathies. Video Abstract.
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Affiliation(s)
- Srishti Chawla
- Institute for Biomedicine, Sahlgrenska Academy, Centre for Ageing and Health - AgeCap, University of Gothenburg, Gothenburg, 405 30, Sweden.
- Department of Life Sciences, Chalmers University of Technology, Gothenburg, Sweden.
| | - Doryaneh Ahmadpour
- Center for Bionics and Pain Research, Sahlgrenska University Hospital, Mölndal, 431 30, Sweden
| | - Kara L Schneider
- Institute for Biomedicine, Sahlgrenska Academy, Centre for Ageing and Health - AgeCap, University of Gothenburg, Gothenburg, 405 30, Sweden
| | - Navinder Kumar
- Institute for Biomedicine, Sahlgrenska Academy, Centre for Ageing and Health - AgeCap, University of Gothenburg, Gothenburg, 405 30, Sweden
| | - Arthur Fischbach
- Max Planck Institute for Biology of Ageing, Cologne, 50931, Germany
| | - Mikael Molin
- Department of Life Sciences, Chalmers University of Technology, Gothenburg, Sweden
| | - Thomas Nystrom
- Institute for Biomedicine, Sahlgrenska Academy, Centre for Ageing and Health - AgeCap, University of Gothenburg, Gothenburg, 405 30, Sweden.
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4
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Cells under pressure: how yeast cells respond to mechanical forces. Trends Microbiol 2022; 30:495-510. [PMID: 35000797 DOI: 10.1016/j.tim.2021.11.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Revised: 10/31/2021] [Accepted: 11/08/2021] [Indexed: 11/23/2022]
Abstract
In their natural habitats, unicellular fungal microbes are exposed to a myriad of mechanical cues such as shear forces from fluid flow, osmotic changes, and contact forces arising from microbial expansion in confined niches. While the rigidity of the cell wall is critical to withstand such external forces and balance high internal turgor pressure, it poses mechanical challenges during physiological processes such as cell growth, division, and mating that require cell wall remodeling. Thus, even organisms as simple as yeast have evolved complex signaling networks to sense and respond to intrinsic and extrinsic mechanical forces. In this review, we summarize the type and origin of mechanical forces experienced by unicellular yeast and discuss how these forces reorganize cell polarity and how pathogenic fungi exploit polarized assemblies to track weak spots in host tissues for successful penetration. We then describe mechanisms of force-sensing by conserved sets of mechanosensors. Finally, we elaborate downstream mechanotransduction mechanisms that orchestrate appropriate cellular responses, leading to improved mechanical fitness.
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5
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Li TN, Chen YJ, Lu TY, Wang YT, Lin HC, Yao CK. A positive feedback loop between Flower and PI(4,5)P 2 at periactive zones controls bulk endocytosis in Drosophila. eLife 2020; 9:60125. [PMID: 33300871 PMCID: PMC7748424 DOI: 10.7554/elife.60125] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Accepted: 12/09/2020] [Indexed: 01/01/2023] Open
Abstract
Synaptic vesicle (SV) endocytosis is coupled to exocytosis to maintain SV pool size and thus neurotransmitter release. Intense stimulation induces activity-dependent bulk endocytosis (ADBE) to recapture large quantities of SV constituents in large endosomes from which SVs reform. How these consecutive processes are spatiotemporally coordinated remains unknown. Here, we show that Flower Ca2+ channel-dependent phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) compartmentalization governs control of these processes in Drosophila. Strong stimuli trigger PI(4,5)P2 microdomain formation at periactive zones. Upon exocytosis, Flower translocates from SVs to periactive zones, where it increases PI(4,5)P2 levels via Ca2+ influxes. Remarkably, PI(4,5)P2 directly enhances Flower channel activity, thereby establishing a positive feedback loop for PI(4,5)P2 microdomain compartmentalization. PI(4,5)P2 microdomains drive ADBE and SV reformation from bulk endosomes. PI(4,5)P2 further retrieves Flower to bulk endosomes, terminating endocytosis. We propose that the interplay between Flower and PI(4,5)P2 is the crucial spatiotemporal cue that couples exocytosis to ADBE and subsequent SV reformation.
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Affiliation(s)
- Tsai-Ning Li
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Yu-Jung Chen
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Ting-Yi Lu
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - You-Tung Wang
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Hsin-Chieh Lin
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Chi-Kuang Yao
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan.,Neuroscience Program of Academia Sinica, Academia Sinica, Taipei, Taiwan.,Institute of Biochemical Sciences, College of Life Science, National Taiwan University, Taipei, Taiwan
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6
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López-Hernández T, Haucke V, Maritzen T. Endocytosis in the adaptation to cellular stress. Cell Stress 2020; 4:230-247. [PMID: 33024932 PMCID: PMC7520666 DOI: 10.15698/cst2020.10.232] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 07/24/2020] [Accepted: 07/29/2020] [Indexed: 12/11/2022] Open
Abstract
Cellular life is challenged by a multitude of stress conditions, triggered for example by alterations in osmolarity, oxygen or nutrient supply. Hence, cells have developed sophisticated stress responses to cope with these challenges. Some of these stress programs such as the heat shock response are understood in great detail, while other aspects remain largely elusive including potential stress-dependent adaptations of the plasma membrane proteome. The plasma membrane is not only the first point of encounter for many types of environmental stress, but given the diversity of receptor proteins and their associated molecules also represents the site at which many cellular signal cascades originate. Since these signaling pathways affect virtually all aspects of cellular life, changes in the plasma membrane proteome appear ideally suited to contribute to the cellular adaptation to stress. The most rapid means to alter the cell surface proteome in response to stress is by alterations in endocytosis. Changes in the overall endocytic flux or in the endocytic regulation of select proteins conceivably can help to counteract adverse environmental conditions. In this review we summarize recent data regarding stress-induced changes in endocytosis and discuss how these changes might contribute to the cellular adaptation to stress in different systems. Future studies will be needed to uncover the underlying mechanisms in detail and to arrive at a coherent picture.
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Affiliation(s)
- Tania López-Hernández
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany
| | - Volker Haucke
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany
- Freie Universität Berlin, Faculty of Biology, Chemistry, Pharmacy, 14195 Berlin, Germany
| | - Tanja Maritzen
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany
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7
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Martínez-Montañés F, Casanovas A, Sprenger RR, Topolska M, Marshall DL, Moreno-Torres M, Poad BL, Blanksby SJ, Hermansson M, Jensen ON, Ejsing CS. Phosphoproteomic Analysis across the Yeast Life Cycle Reveals Control of Fatty Acyl Chain Length by Phosphorylation of the Fatty Acid Synthase Complex. Cell Rep 2020; 32:108024. [DOI: 10.1016/j.celrep.2020.108024] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Revised: 05/11/2020] [Accepted: 07/21/2020] [Indexed: 12/12/2022] Open
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8
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Wigington CP, Roy J, Damle NP, Yadav VK, Blikstad C, Resch E, Wong CJ, Mackay DR, Wang JT, Krystkowiak I, Bradburn DA, Tsekitsidou E, Hong SH, Kaderali MA, Xu SL, Stearns T, Gingras AC, Ullman KS, Ivarsson Y, Davey NE, Cyert MS. Systematic Discovery of Short Linear Motifs Decodes Calcineurin Phosphatase Signaling. Mol Cell 2020; 79:342-358.e12. [PMID: 32645368 DOI: 10.1016/j.molcel.2020.06.029] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Revised: 03/24/2020] [Accepted: 05/26/2020] [Indexed: 12/17/2022]
Abstract
Short linear motifs (SLiMs) drive dynamic protein-protein interactions essential for signaling, but sequence degeneracy and low binding affinities make them difficult to identify. We harnessed unbiased systematic approaches for SLiM discovery to elucidate the regulatory network of calcineurin (CN)/PP2B, the Ca2+-activated phosphatase that recognizes LxVP and PxIxIT motifs. In vitro proteome-wide detection of CN-binding peptides, in vivo SLiM-dependent proximity labeling, and in silico modeling of motif determinants uncovered unanticipated CN interactors, including NOTCH1, which we establish as a CN substrate. Unexpectedly, CN shows SLiM-dependent proximity to centrosomal and nuclear pore complex (NPC) proteins-structures where Ca2+ signaling is largely uncharacterized. CN dephosphorylates human and yeast NPC proteins and promotes accumulation of a nuclear transport reporter, suggesting conserved NPC regulation by CN. The CN network assembled here provides a resource to investigate Ca2+ and CN signaling and demonstrates synergy between experimental and computational methods, establishing a blueprint for examining SLiM-based networks.
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Affiliation(s)
| | - Jagoree Roy
- Department of Biology, Stanford University, Stanford, CA, USA
| | - Nikhil P Damle
- Department of Biology, Stanford University, Stanford, CA, USA
| | - Vikash K Yadav
- Department of Chemistry - BMC, Uppsala University, Uppsala, Sweden
| | - Cecilia Blikstad
- Department of Chemistry - BMC, Uppsala University, Uppsala, Sweden
| | - Eduard Resch
- Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Branch for Translational Medicine and Pharmacology TMP, Theodor-Stern-Kai 7, 60596 Frankfurt am Main, Germany
| | - Cassandra J Wong
- Lunenfeld-Tanenbaum Research Institute at Mount Sinai Hospital, University of Toronto, Toronto, ON, Canada
| | - Douglas R Mackay
- Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah, Salt Lake City, UT, USA
| | - Jennifer T Wang
- Department of Biology, Stanford University, Stanford, CA, USA
| | - Izabella Krystkowiak
- Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland
| | | | | | - Su Hyun Hong
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA, USA
| | - Malika Amyn Kaderali
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA, USA
| | - Shou-Ling Xu
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA, USA
| | - Tim Stearns
- Department of Biology, Stanford University, Stanford, CA, USA
| | - Anne-Claude Gingras
- Lunenfeld-Tanenbaum Research Institute at Mount Sinai Hospital, University of Toronto, Toronto, ON, Canada; Department of Molecular Genetics, University of Toronto, Toronto, M5S 3H7 ON, Canada
| | - Katharine S Ullman
- Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah, Salt Lake City, UT, USA
| | - Ylva Ivarsson
- Department of Chemistry - BMC, Uppsala University, Uppsala, Sweden
| | - Norman E Davey
- Division of Cancer Biology, The Institute of Cancer Research, 237 Fullham Road, London SW3 6JB, UK
| | - Martha S Cyert
- Department of Biology, Stanford University, Stanford, CA, USA.
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9
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Roy J, Cyert MS. Identifying New Substrates and Functions for an Old Enzyme: Calcineurin. Cold Spring Harb Perspect Biol 2020; 12:a035436. [PMID: 31308145 PMCID: PMC7050593 DOI: 10.1101/cshperspect.a035436] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Biological processes are dynamically regulated by signaling networks composed of protein kinases and phosphatases. Calcineurin, or PP3, is a conserved phosphoserine/phosphothreonine-specific protein phosphatase and member of the PPP family of phosphatases. Calcineurin is unique, however, in its activation by Ca2+ and calmodulin. This ubiquitously expressed phosphatase controls Ca2+-dependent processes in all human tissues, but is best known for driving the adaptive immune response by dephosphorylating the nuclear factor of the activated T-cells (NFAT) family of transcription factors. Therefore, calcineurin inhibitors, FK506 (tacrolimus), and cyclosporin A serve as immunosuppressants. We describe some of the adverse effects associated with calcineurin inhibitors that result from inhibition of calcineurin in nonimmune tissues, illustrating the many functions of this enzyme that have yet to be elucidated. In fact, calcineurin has essential roles beyond the immune system, from yeast to humans, but since its discovery more than 30 years ago, only a small number of direct calcineurin substrates have been shown (∼75 proteins). This is because of limitations in current methods for identification of phosphatase substrates. Here we discuss recent insights into mechanisms of calcineurin activation and substrate recognition that have been critical in the development of novel approaches for identifying its targets systematically. Rather than comprehensively reviewing known functions of calcineurin, we highlight new approaches to substrate identification for this critical regulator that may reveal molecular mechanisms underlying toxicities caused by calcineurin inhibitor-based immunosuppression.
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Affiliation(s)
- Jagoree Roy
- Department of Biology, Stanford University, Stanford, California 94305-5020
| | - Martha S Cyert
- Department of Biology, Stanford University, Stanford, California 94305-5020
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10
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Compensatory Internalization of Pma1 in V-ATPase Mutants in Saccharomyces cerevisiae Requires Calcium- and Glucose-Sensitive Phosphatases. Genetics 2017; 208:655-672. [PMID: 29254995 PMCID: PMC5788529 DOI: 10.1534/genetics.117.300594] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Accepted: 12/09/2017] [Indexed: 11/23/2022] Open
Abstract
Loss of V-ATPase activity in organelles triggers compensatory endocytic downregulation of the plasma membrane proton pump Pma1. Here, Velivela and Kane... Loss of V-ATPase activity in organelles, whether through V-ATPase inhibition or V-ATPase (vma) mutations, triggers a compensatory downregulation of the essential plasma membrane proton pump Pma1 in Saccharomyces cerevisiae. We have previously determined that the α-arrestin Rim8 and ubiquitin ligase Rsp5 are essential for Pma1 ubiquination and endocytosis in response to loss of V-ATPase activity. Here, we show that Pma1 endocytosis in V-ATPase mutants does not require Rim101 pathway components upstream and downstream of Rim8, indicating that Rim8 is acting independently in Pma1 internalization. We find that two phosphatases, the calcium-responsive phosphatase calcineurin and the glucose-sensitive phosphatase Glc7 (PP1), and one of the Glc7 regulatory subunits Reg1, exhibit negative synthetic genetic interactions with vma mutants, and demonstrate that both phosphatases are essential for ubiquitination and endocytic downregulation of Pma1 in these mutants. Although both acute and chronic loss of V-ATPase activity trigger the internalization of ∼50% of surface Pma1, a comparable reduction in Pma1 expression in a pma1-007 mutant neither compensates for loss of V-ATPase activity nor stops further Pma1 endocytosis. The results indicate that the cell surface level of Pma1 is not directly sensed and that internalized Pma1 may play a role in compensating for loss of V-ATPase-dependent acidification. Taken together, these results provide new insights into cross talk between two major proton pumps central to cellular pH control.
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11
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Protein kinase C and calcineurin cooperatively mediate cell survival under compressive mechanical stress. Proc Natl Acad Sci U S A 2017; 114:13471-13476. [PMID: 29196524 DOI: 10.1073/pnas.1709079114] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Cells experience compressive stress while growing in limited space or migrating through narrow constrictions. To survive such stress, cells reprogram their intracellular organization to acquire appropriate mechanical properties. However, the mechanosensors and downstream signaling networks mediating these changes remain largely unknown. Here, we have established a microfluidic platform to specifically trigger compressive stress, and to quantitatively monitor single-cell responses of budding yeast in situ. We found that yeast senses compressive stress via the cell surface protein Mid2 and the calcium channel proteins Mid1 and Cch1, which then activate the Pkc1/Mpk1 MAP kinase pathway and calcium signaling, respectively. Genetic analysis revealed that these pathways work in parallel to mediate cell survival. Mid2 contains a short intracellular tail and a serine-threonine-rich extracellular domain with spring-like properties, and both domains are required for mechanosignaling. Mid2-dependent spatial activation of the Pkc1/Mpk1 pathway depolarizes the actin cytoskeleton in budding or shmooing cells, thereby antagonizing polarized growth to protect cells under compressive stress conditions. Together, these results identify a conserved signaling network responding to compressive mechanical stress, which, in higher eukaryotes, may ensure cell survival in confined environments.
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12
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Ly N, Cyert MS. Calcineurin, the Ca 2+-dependent phosphatase, regulates Rga2, a Cdc42 GTPase-activating protein, to modulate pheromone signaling. Mol Biol Cell 2017; 28:576-586. [PMID: 28077617 PMCID: PMC5328617 DOI: 10.1091/mbc.e16-06-0432] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Revised: 01/04/2017] [Accepted: 01/04/2017] [Indexed: 11/11/2022] Open
Abstract
Calcineurin, the conserved Ca2+/calmodulin-activated phosphatase, is required for viability during prolonged exposure to pheromone and acts through multiple substrates to down-regulate yeast pheromone signaling. Calcineurin regulates Dig2 and Rod1/Art4 to inhibit mating-induced gene expression and activate receptor internalization, respectively. Recent systematic approaches identified Rga2, a GTPase-activating protein (GAP) for the Cdc42 Rho-type GTPase, as a calcineurin substrate. Here we establish a physiological context for this regulation and show that calcineurin dephosphorylates and positively regulates Rga2 during pheromone signaling. Mating factor activates the Fus3/MAPK kinase, whose substrates induce gene expression, cell cycle arrest, and formation of the mating projection. Our studies demonstrate that Fus3 also phosphorylates Rga2 at inhibitory S/TP sites, which are targeted by Cdks during the cell cycle, and that calcineurin opposes Fus3 to activate Rga2 and decrease Cdc42 signaling. Yeast expressing an Rga2 mutant that is defective for regulation by calcineurin display increased gene expression in response to pheromone. This work is the first to identify cross-talk between Ca2+/calcineurin and Cdc42 signaling and to demonstrate modulation of Cdc42 activity through a GAP during mating.
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Affiliation(s)
- Nina Ly
- Department of Biology, Stanford University, Stanford, CA 94305
| | - Martha S Cyert
- Department of Biology, Stanford University, Stanford, CA 94305
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13
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Carquin M, D'Auria L, Pollet H, Bongarzone ER, Tyteca D. Recent progress on lipid lateral heterogeneity in plasma membranes: From rafts to submicrometric domains. Prog Lipid Res 2015; 62:1-24. [PMID: 26738447 DOI: 10.1016/j.plipres.2015.12.004] [Citation(s) in RCA: 103] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 12/22/2015] [Accepted: 12/22/2015] [Indexed: 12/29/2022]
Abstract
The concept of transient nanometric domains known as lipid rafts has brought interest to reassess the validity of the Singer-Nicolson model of a fluid bilayer for cell membranes. However, this new view is still insufficient to explain the cellular control of surface lipid diversity or membrane deformability. During the past decades, the hypothesis that some lipids form large (submicrometric/mesoscale vs nanometric rafts) and stable (>min vs s) membrane domains has emerged, largely based on indirect methods. Morphological evidence for stable submicrometric lipid domains, well-accepted for artificial and highly specialized biological membranes, was further reported for a variety of living cells from prokaryot es to yeast and mammalian cells. However, results remained questioned based on limitations of available fluorescent tools, use of poor lipid fixatives, and imaging artifacts due to non-resolved membrane projections. In this review, we will discuss recent evidence generated using powerful and innovative approaches such as lipid-specific toxin fragments that support the existence of submicrometric domains. We will integrate documented mechanisms involved in the formation and maintenance of these domains, and provide a perspective on their relevance on membrane deformability and regulation of membrane protein distribution.
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Affiliation(s)
- Mélanie Carquin
- CELL Unit, de Duve Institute & Université Catholique de Louvain, UCL B1.75.05, Avenue Hippocrate, 75, B-1200 Brussels, Belgium
| | - Ludovic D'Auria
- The Myelin Regeneration Group at the Dept. Anatomy & Cell Biology, College of Medicine, University of Illinois, 808 S. Wood St. MC512, Chicago, IL. 60612. USA
| | - Hélène Pollet
- CELL Unit, de Duve Institute & Université Catholique de Louvain, UCL B1.75.05, Avenue Hippocrate, 75, B-1200 Brussels, Belgium
| | - Ernesto R Bongarzone
- The Myelin Regeneration Group at the Dept. Anatomy & Cell Biology, College of Medicine, University of Illinois, 808 S. Wood St. MC512, Chicago, IL. 60612. USA
| | - Donatienne Tyteca
- CELL Unit, de Duve Institute & Université Catholique de Louvain, UCL B1.75.05, Avenue Hippocrate, 75, B-1200 Brussels, Belgium.
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Smaczynska-de Rooij II, Marklew CJ, Allwood EG, Palmer SE, Booth WI, Mishra R, Goldberg MW, Ayscough KR. Phosphorylation Regulates the Endocytic Function of the Yeast Dynamin-Related Protein Vps1. Mol Cell Biol 2015; 36:742-55. [PMID: 26711254 PMCID: PMC4760221 DOI: 10.1128/mcb.00833-15] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Revised: 10/08/2015] [Accepted: 12/10/2015] [Indexed: 12/25/2022] Open
Abstract
The family of dynamin proteins is known to function in many eukaryotic membrane fusion and fission events. The yeast dynamin-related protein Vps1 functions at several stages of membrane trafficking, including Golgi apparatus to endosome and vacuole, peroxisomal fission, and endocytic scission. We have previously shown that in its endocytic role, Vps1 functions with the amphiphysin heterodimer Rvs161/Rvs167 to facilitate scission and release of vesicles. Phosphoproteome studies of Saccharomyces cerevisiae have identified a phosphorylation site in Vps1 at serine 599. In this study, we confirmed this phosphorylation event, and we reveal that, like Rvs167, Vps1 can be phosphorylated by the yeast cyclin-associated kinase Pho85 in vivo and in vitro. The importance of this posttranslational modification was revealed when mutagenesis of S599 to a phosphomimetic or nonphosphorylatable form caused defects in endocytosis but not in other functions associated with Vps1. Mutation to nonphosphorylatable valine inhibited the Rvs167 interaction, while both S599V and S599D caused defects in vesicle scission, as shown by both live-cell imaging and electron microscopy of endocytic invaginations. Our data support a model in which phosphorylation and dephosphorylation of Vps1 promote distinct interactions and highlight the importance of such regulatory events in facilitating sequential progression of the endocytic process.
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Affiliation(s)
| | - Christopher J Marklew
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
| | - Ellen G Allwood
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
| | - Sarah E Palmer
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
| | - Wesley I Booth
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
| | - Ritu Mishra
- School of Biological and Biomedical Sciences, Durham University, Durham, United Kingdom
| | - Martin W Goldberg
- School of Biological and Biomedical Sciences, Durham University, Durham, United Kingdom
| | - Kathryn R Ayscough
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
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15
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Kabeche R, Madrid M, Cansado J, Moseley JB. Eisosomes Regulate Phosphatidylinositol 4,5-Bisphosphate (PI(4,5)P2) Cortical Clusters and Mitogen-activated Protein (MAP) Kinase Signaling upon Osmotic Stress. J Biol Chem 2015; 290:25960-73. [PMID: 26359496 DOI: 10.1074/jbc.m115.674192] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Indexed: 01/22/2023] Open
Abstract
Eisosomes are multiprotein structures that generate linear invaginations at the plasma membrane of yeast cells. The core component of eisosomes, the BAR domain protein Pil1, generates these invaginations through direct binding to lipids including phosphoinositides. Eisosomes promote hydrolysis of phosphatidylinositol 4,5 bisphosphate (PI(4,5)P2) by functioning with synaptojanin, but the cellular processes regulated by this pathway have been unknown. Here, we found that PI(4,5)P2 regulation by eisosomes inhibits the cell integrity pathway, a conserved MAPK signal transduction cascade. This pathway is activated by multiple environmental conditions including osmotic stress in the fission yeast Schizosaccharomyces pombe. Activation of the MAPK Pmk1 was impaired by mutations in the phosphatidylinositol (PI) 5-kinase Its3, but this defect was suppressed by removal of eisosomes. Using fluorescent biosensors, we found that osmotic stress induced the formation of PI(4,5)P2 clusters that were spatially organized by eisosomes in both fission yeast and budding yeast cells. These cortical clusters contained the PI 5-kinase Its3 and did not assemble in the its3-1 mutant. The GTPase Rho2, an upstream activator of Pmk1, also co-localized with PI(4,5)P2 clusters under osmotic stress, providing a molecular link between these novel clusters and MAPK activation. Our findings have revealed that eisosomes regulate activation of MAPK signal transduction through the organization of cortical lipid-based microdomains.
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Affiliation(s)
- Ruth Kabeche
- From the Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755 and
| | - Marisa Madrid
- Yeast Physiology Group, Department of Genetics and Microbiology, Facultad de Biología, Universidad de Murcia, 30071, Murcia, Spain
| | - José Cansado
- Yeast Physiology Group, Department of Genetics and Microbiology, Facultad de Biología, Universidad de Murcia, 30071, Murcia, Spain
| | - James B Moseley
- From the Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755 and
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16
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Muir A, Roelants FM, Timmons G, Leskoske KL, Thorner J. Down-regulation of TORC2-Ypk1 signaling promotes MAPK-independent survival under hyperosmotic stress. eLife 2015; 4. [PMID: 26274562 PMCID: PMC4552222 DOI: 10.7554/elife.09336] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Accepted: 08/13/2015] [Indexed: 01/10/2023] Open
Abstract
In eukaryotes, exposure to hypertonic conditions activates a MAPK (Hog1 in Saccharomyces cerevisiae and ortholog p38 in human cells). In yeast, intracellular glycerol accumulates to counterbalance the high external osmolarity. To prevent glycerol efflux, Hog1 action impedes the function of the aquaglyceroporin Fps1, in part, by displacing channel co-activators (Rgc1/2). However, Fps1 closes upon hyperosmotic shock even in hog1∆ cells, indicating another mechanism to prevent Fps1-mediated glycerol efflux. In our prior proteome-wide screen, Fps1 was identified as a target of TORC2-dependent protein kinase Ypk1 (Muir et al., 2014). We show here that Fps1 is an authentic Ypk1 substrate and that the open channel state of Fps1 requires phosphorylation by Ypk1. Moreover, hyperosmotic conditions block TORC2-dependent Ypk1-mediated Fps1 phosphorylation, causing channel closure, glycerol accumulation, and enhanced survival under hyperosmotic stress. These events are all Hog1-independent. Our findings define the underlying molecular basis of a new mechanism for responding to hypertonic conditions. DOI:http://dx.doi.org/10.7554/eLife.09336.001
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Affiliation(s)
- Alexander Muir
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Françoise M Roelants
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Garrett Timmons
- Department of Chemistry, University of California, Berkeley, Berkeley, United States
| | - Kristin L Leskoske
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Jeremy Thorner
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
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17
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Arsenault HE, Roy J, Mapa CE, Cyert MS, Benanti JA. Hcm1 integrates signals from Cdk1 and calcineurin to control cell proliferation. Mol Biol Cell 2015; 26:3570-7. [PMID: 26269584 PMCID: PMC4603928 DOI: 10.1091/mbc.e15-07-0469] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Accepted: 08/06/2015] [Indexed: 11/23/2022] Open
Abstract
The transcription factor Hcm1 is a key regulator of chromosome segregation and genome stability. The phosphatase calcineurin directly inactivates Hcm1 in response to environmental stress, which inhibits proliferation. Hcm1 functions as a rheostat, whose phosphorylation state affects the rate of proliferation. Cyclin-dependent kinase (Cdk1) orchestrates progression through the cell cycle by coordinating the activities of cell-cycle regulators. Although phosphatases that oppose Cdk1 are likely to be necessary to establish dynamic phosphorylation, specific phosphatases that target most Cdk1 substrates have not been identified. In budding yeast, the transcription factor Hcm1 activates expression of genes that regulate chromosome segregation and is critical for maintaining genome stability. Previously we found that Hcm1 activity and degradation are stimulated by Cdk1 phosphorylation of distinct clusters of sites. Here we show that, upon exposure to environmental stress, the phosphatase calcineurin inhibits Hcm1 by specifically removing activating phosphorylations and that this regulation is important for cells to delay proliferation when they encounter stress. Our work identifies a mechanism by which proliferative signals from Cdk1 are removed in response to stress and suggests that Hcm1 functions as a rheostat that integrates stimulatory and inhibitory signals to control cell proliferation.
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Affiliation(s)
- Heather E Arsenault
- Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, Worcester, MA 01520
| | - Jagoree Roy
- Department of Biology, Stanford University, Stanford, CA 94305
| | - Claudine E Mapa
- Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, Worcester, MA 01520
| | - Martha S Cyert
- Department of Biology, Stanford University, Stanford, CA 94305
| | - Jennifer A Benanti
- Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, Worcester, MA 01520
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