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Jin N, Jin Y, Oikawa Y, Nakano A, Ohsumi Y, Weisman LS. A non-canonical CDK, Pho85 regulates the restart of the cell-cycle following stress. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.08.27.609989. [PMID: 39253458 PMCID: PMC11383280 DOI: 10.1101/2024.08.27.609989] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/11/2024]
Abstract
Environmental stress induces an arrest of the cell cycle. Thus, release from this arrest is essential for cell survival. The cell-cycle-arrest occurs via the down regulation of the cyclins that drive the main cyclin dependent kinase, CDK1/Cdc28. However, it was not clear how cells escape this potentially fatal arrest. Here we show that prior to the restoration of CDK1/Cdc28 cyclins, a non-canonical CDK, Pho85, initiates a cascade to restart the cell cycle. We demonstrate that following stress, Pho85 phosphorylates the Sch9 kinase, which in turn directly phosphorylates the transcriptional inhibitor Whi5, the yeast analog of RB1/retinoblastoma, and a CDK1 target. This promotes Whi5 translocation from the nucleus, and the release of the stress-induced arrest at G 1 phase. In addition, we find that in parallel with Pho85, CDK1/Cdc28 also plays a role in the control of Whi5. Together, these findings provide insights into how cells re-enter the cell cycle during recovery from stress and reveal that a non-canonical CDK and cyclin takes on essential roles and acts via a pathway that functions in parallel with CDK1/Cdc28.
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2
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Creamer DR, Beynon RJ, Hubbard SJ, Ashe MP, Grant CM. Isoform-specific sequestration of protein kinase A fine-tunes intracellular signaling during heat stress. Cell Rep 2024; 43:114360. [PMID: 38865242 DOI: 10.1016/j.celrep.2024.114360] [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: 12/22/2023] [Revised: 04/24/2024] [Accepted: 05/30/2024] [Indexed: 06/14/2024] Open
Abstract
Protein kinase A (PKA) is a conserved kinase crucial for fundamental biological processes linked to growth, development, and metabolism. The PKA catalytic subunit is expressed as multiple isoforms in diverse eukaryotes; however, their contribution to ensuring signaling specificity in response to environmental cues remains poorly defined. Catalytic subunit activity is classically moderated via interaction with an inhibitory regulatory subunit. Here, a quantitative mass spectrometry approach is used to examine heat-stress-induced changes in the binding of yeast Tpk1-3 catalytic subunits to the Bcy1 regulatory subunit. We show that Tpk3 is not regulated by Bcy1 binding but, instead, is deactivated upon heat stress via reversible sequestration into cytoplasmic granules. These "Tpk3 granules" are enriched for multiple PKA substrates involved in various metabolic processes, with the Hsp42 sequestrase required for their formation. Hence, regulated sequestration of Tpk3 provides a mechanism to control isoform-specific kinase signaling activity during stress conditions.
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Affiliation(s)
- Declan R Creamer
- Faculty of Biology, Medicine and Health, The University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK
| | - Robert J Beynon
- Centre for Proteome Research, Institute of Systems and Integrative Biology, University of Liverpool, Crown Street, Liverpool L69 7ZB, UK
| | - Simon J Hubbard
- Faculty of Biology, Medicine and Health, The University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK
| | - Mark P Ashe
- Faculty of Biology, Medicine and Health, The University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK
| | - Chris M Grant
- Faculty of Biology, Medicine and Health, The University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK.
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3
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Plank M, Carmiol N, Mitri B, Lipinski AA, Langlais PR, Capaldi AP. Systems level analysis of time and stimuli specific signaling through PKA. Mol Biol Cell 2024; 35:ar60. [PMID: 38446618 PMCID: PMC11064662 DOI: 10.1091/mbc.e23-02-0066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Revised: 02/13/2024] [Accepted: 03/01/2024] [Indexed: 03/08/2024] Open
Abstract
It is well known that eukaryotic cells create gradients of cAMP across space and time to regulate the cAMP dependent protein kinase (PKA) and, in turn, growth and metabolism. However, it is unclear how PKA responds to different concentrations of cAMP. Here, to address this question, we examine PKA signaling in Saccharomyces cerevisiae in different conditions, timepoints, and concentrations of the chemical inhibitor 1-NM-PP1, using phosphoproteomics. These experiments show that there are numerous proteins that are only phosphorylated when cAMP and PKA activity are at/near their maximum level, while other proteins are phosphorylated even when cAMP levels and PKA activity are low. The data also show that PKA drives cells into distinct growth states by acting on proteins with different thresholds for phosphorylation in different conditions. Analysis of the sequences surrounding the 118 PKA-dependent phosphosites suggests that the phosphorylation thresholds are set, at least in part, by the affinity of PKA for each site.
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Affiliation(s)
- Michael Plank
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ 85721
- The Bio5 Institute, University of Arizona, Tucson, AZ 85721
| | - Nicole Carmiol
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ 85721
| | - Bassam Mitri
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ 85721
| | | | - Paul R. Langlais
- The Department of Medicine, University of Arizona, Tucson, AZ 85721
| | - Andrew P. Capaldi
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ 85721
- The Bio5 Institute, University of Arizona, Tucson, AZ 85721
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4
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Leutert M, Barente AS, Fukuda NK, Rodriguez-Mias RA, Villén J. The regulatory landscape of the yeast phosphoproteome. Nat Struct Mol Biol 2023; 30:1761-1773. [PMID: 37845410 PMCID: PMC10841839 DOI: 10.1038/s41594-023-01115-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2023] [Accepted: 09/05/2023] [Indexed: 10/18/2023]
Abstract
The cellular ability to react to environmental fluctuations depends on signaling networks that are controlled by the dynamic activities of kinases and phosphatases. Here, to gain insight into these stress-responsive phosphorylation networks, we generated a quantitative mass spectrometry-based atlas of early phosphoproteomic responses in Saccharomyces cerevisiae exposed to 101 environmental and chemical perturbations. We report phosphosites on 59% of the yeast proteome, with 18% of the proteome harboring a phosphosite that is regulated within 5 min of stress exposure. We identify shared and perturbation-specific stress response programs, uncover loss of phosphorylation as an integral early event, and dissect the interconnected regulatory landscape of kinase-substrate networks, as we exemplify with target of rapamycin signaling. We further reveal functional organization principles of the stress-responsive phosphoproteome based on phosphorylation site motifs, kinase activities, subcellular localizations, shared functions and pathway intersections. This information-rich map of 25,000 regulated phosphosites advances our understanding of signaling networks.
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Affiliation(s)
- Mario Leutert
- Department of Genome Sciences, University of Washington, Seattle, WA, USA.
| | - Anthony S Barente
- Department of Genome Sciences, University of Washington, Seattle, WA, USA
| | - Noelle K Fukuda
- Department of Genome Sciences, University of Washington, Seattle, WA, USA
| | | | - Judit Villén
- Department of Genome Sciences, University of Washington, Seattle, WA, USA.
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5
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DeMarco AG, Hall MC. Phosphoproteomic Approaches for Identifying Phosphatase and Kinase Substrates. Molecules 2023; 28:3675. [PMID: 37175085 PMCID: PMC10180314 DOI: 10.3390/molecules28093675] [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: 04/07/2023] [Revised: 04/21/2023] [Accepted: 04/22/2023] [Indexed: 05/15/2023] Open
Abstract
Protein phosphorylation is a ubiquitous post-translational modification controlled by the opposing activities of protein kinases and phosphatases, which regulate diverse biological processes in all kingdoms of life. One of the key challenges to a complete understanding of phosphoregulatory networks is the unambiguous identification of kinase and phosphatase substrates. Liquid chromatography-coupled mass spectrometry (LC-MS/MS) and associated phosphoproteomic tools enable global surveys of phosphoproteome changes in response to signaling events or perturbation of phosphoregulatory network components. Despite the power of LC-MS/MS, it is still challenging to directly link kinases and phosphatases to specific substrate phosphorylation sites in many experiments. Here, we survey common LC-MS/MS-based phosphoproteomic workflows for identifying protein kinase and phosphatase substrates, noting key advantages and limitations of each. We conclude by discussing the value of inducible degradation technologies coupled with phosphoproteomics as a new approach that overcomes some limitations of current methods for substrate identification of kinases, phosphatases, and other regulatory enzymes.
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Affiliation(s)
- Andrew G. DeMarco
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907, USA
| | - Mark C. Hall
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907, USA
- Institute for Cancer Research, Purdue University, West Lafayette, IN 47907, USA
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6
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Abstract
Most cells live in environments that are permissive for proliferation only a small fraction of the time. Entering quiescence enables cells to survive long periods of nondivision and reenter the cell cycle when signaled to do so. Here, we describe what is known about the molecular basis for quiescence in Saccharomyces cerevisiae, with emphasis on the progress made in the last decade. Quiescence is triggered by depletion of an essential nutrient. It begins well before nutrient exhaustion, and there is extensive crosstalk between signaling pathways to ensure that all proliferation-specific activities are stopped when any one essential nutrient is limiting. Every aspect of gene expression is modified to redirect and conserve resources. Chromatin structure and composition change on a global scale, from histone modifications to three-dimensional chromatin structure. Thousands of proteins and RNAs aggregate, forming unique structures with unique fates, and the cytoplasm transitions to a glass-like state.
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Affiliation(s)
- Linda L Breeden
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, Washington, USA; ,
| | - Toshio Tsukiyama
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, Washington, USA; ,
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Thorner J. TOR complex 2 is a master regulator of plasma membrane homeostasis. Biochem J 2022; 479:1917-1940. [PMID: 36149412 PMCID: PMC9555796 DOI: 10.1042/bcj20220388] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Revised: 08/30/2022] [Accepted: 09/01/2022] [Indexed: 11/17/2022]
Abstract
As first demonstrated in budding yeast (Saccharomyces cerevisiae), all eukaryotic cells contain two, distinct multi-component protein kinase complexes that each harbor the TOR (Target Of Rapamycin) polypeptide as the catalytic subunit. These ensembles, dubbed TORC1 and TORC2, function as universal, centrally important sensors, integrators, and controllers of eukaryotic cell growth and homeostasis. TORC1, activated on the cytosolic surface of the lysosome (or, in yeast, on the cytosolic surface of the vacuole), has emerged as a primary nutrient sensor that promotes cellular biosynthesis and suppresses autophagy. TORC2, located primarily at the plasma membrane, plays a major role in maintaining the proper levels and bilayer distribution of all plasma membrane components (sphingolipids, glycerophospholipids, sterols, and integral membrane proteins). This article surveys what we have learned about signaling via the TORC2 complex, largely through studies conducted in S. cerevisiae. In this yeast, conditions that challenge plasma membrane integrity can, depending on the nature of the stress, stimulate or inhibit TORC2, resulting in, respectively, up-regulation or down-regulation of the phosphorylation and thus the activity of its essential downstream effector the AGC family protein kinase Ypk1. Through the ensuing effect on the efficiency with which Ypk1 phosphorylates multiple substrates that control diverse processes, membrane homeostasis is maintained. Thus, the major focus here is on TORC2, Ypk1, and the multifarious targets of Ypk1 and how the functions of these substrates are regulated by their Ypk1-mediated phosphorylation, with emphasis on recent advances in our understanding of these processes.
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Affiliation(s)
- Jeremy Thorner
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3202, U.S.A
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Phosphorylation of Jhd2 by the Ras-cAMP-PKA(Tpk2) pathway regulates histone modifications and autophagy. Nat Commun 2022; 13:5675. [PMID: 36167807 PMCID: PMC9515143 DOI: 10.1038/s41467-022-33423-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Accepted: 09/16/2022] [Indexed: 11/12/2022] Open
Abstract
Cells need to coordinate gene expression with their metabolic states to maintain cell homeostasis and growth. How cells transduce nutrient availability to appropriate gene expression remains poorly understood. Here we show that glycolysis regulates histone modifications and gene expression by activating protein kinase A (PKA) via the Ras-cyclic AMP pathway. The catalytic subunit of PKA, Tpk2 antagonizes Jhd2-catalyzed H3K4 demethylation by phosphorylating Jhd2 at Ser321 and Ser340 in response to glucose availability. Tpk2-catalyzed Jhd2 phosphorylation impairs its nuclear localization, reduces its binding to chromatin, and promotes its polyubiquitination and degradation by the proteasome. Tpk2-catalyzed Jhd2 phosphorylation also maintains H3K14 acetylation by preventing the binding of histone deacetylase Rpd3 to chromatin. By phosphorylating Jhd2, Tpk2 regulates gene expression, maintains normal chronological life span and promotes autophagy. These results provide a direct connection between metabolism and histone modifications and shed lights on how cells rewire their biological responses to nutrient signals. How cells transduce nutrient availability to appropriate gene expression remains poorly understood. Here the authors show that the nutrient sensor, protein kinase A modulates histone modifications and gene transcription by phosphorylating histone demethylase.
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Interaction of TOR and PKA Signaling in S. cerevisiae. Biomolecules 2022; 12:biom12020210. [PMID: 35204711 PMCID: PMC8961621 DOI: 10.3390/biom12020210] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Revised: 01/22/2022] [Accepted: 01/25/2022] [Indexed: 01/13/2023] Open
Abstract
TOR and PKA signaling are the major growth-regulatory nutrient-sensing pathways in S. cerevisiae. A number of experimental findings demonstrated a close relationship between these pathways: Both are responsive to glucose availability. Both regulate ribosome production on the transcriptional level and repress autophagy and the cellular stress response. Sch9, a major downstream effector of TORC1 presumably shares its kinase consensus motif with PKA, and genetic rescue and synthetic defects between PKA and Sch9 have been known for a long time. Further, studies in the first decade of this century have suggested direct regulation of PKA by TORC1. Nonetheless, the contribution of a potential direct cross-talk vs. potential sharing of targets between the pathways has still not been completely resolved. What is more, other findings have in contrast highlighted an antagonistic relationship between the two pathways. In this review, I explore the association between TOR and PKA signaling, mainly by focusing on proteins that are commonly referred to as shared TOR and PKA targets. Most of these proteins are transcription factors which to a large part explain the major transcriptional responses elicited by TOR and PKA upon nutrient shifts. I examine the evidence that these proteins are indeed direct targets of both pathways and which aspects of their regulation are targeted by TOR and PKA. I further explore if they are phosphorylated on shared sites by PKA and Sch9 or when experimental findings point towards regulation via the PP2ASit4/PP2A branch downstream of TORC1. Finally, I critically review data suggesting direct cross-talk between the pathways and its potential mechanism.
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10
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Colombo S, Longoni E, Gnugnoli M, Busti S, Martegani E. Fast detection of PKA activity in Saccharomyces cerevisiae cell population using AKAR fluorescence resonance energy transfer probes. Cell Signal 2022; 92:110262. [DOI: 10.1016/j.cellsig.2022.110262] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Revised: 12/23/2021] [Accepted: 01/20/2022] [Indexed: 11/03/2022]
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11
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Phosphoproteomic responses of TORC1 target kinases reveal discrete and convergent mechanisms that orchestrate the quiescence program in yeast. Cell Rep 2021; 37:110149. [PMID: 34965436 DOI: 10.1016/j.celrep.2021.110149] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Revised: 10/19/2021] [Accepted: 11/30/2021] [Indexed: 01/18/2023] Open
Abstract
The eukaryotic TORC1 kinase assimilates diverse environmental cues, including growth factors and nutrients, to control growth by tuning anabolic and catabolic processes. In yeast, TORC1 stimulates protein synthesis in response to abundant nutrients primarily through its proximal effector kinase Sch9. Conversely, TORC1 inhibition following nutrient limitation unlocks various distally controlled kinases (e.g., Atg1, Gcn2, Npr1, Rim15, Slt2/Mpk1, and Yak1), which cooperate through poorly defined circuits to orchestrate the quiescence program. To better define the signaling landscape of the latter kinases, we use in vivo quantitative phosphoproteomics. Through pinpointing known and uncharted Npr1, Rim15, Slt2/Mpk1, and Yak1 effectors, our study examines the architecture of the distally controlled TORC1 kinase network. Accordingly, this is built on a combination of discrete, convergent, and multilayered feedback regulatory mechanisms, which likely ensure homeostatic control of and/or robust responses by TORC1 and its effector kinases under fluctuating nutritional conditions.
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12
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Peterson PP, Liu Z. Identification and Characterization of Rapidly Accumulating sch9Δ Suppressor Mutations in Saccharomyces cerevisiae. G3-GENES GENOMES GENETICS 2021; 11:6254187. [PMID: 33901283 DOI: 10.1093/g3journal/jkab134] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2021] [Accepted: 04/14/2021] [Indexed: 01/30/2023]
Abstract
Nutrient sensing is important for cell growth, aging, and longevity. In Saccharomyces cerevisiae, Sch9, an AGC-family protein kinase, is a major nutrient sensing kinase homologous to mammalian Akt and S6 kinase. Sch9 integrates environmental cues with cell growth by functioning downstream of TORC1 and in parallel with the Ras/PKA pathway. Mutations in SCH9 lead to reduced cell growth in dextrose medium; however, reports on the ability of sch9Δ mutants to utilize non-fermentable carbon sources are inconsistent. Here we show that sch9Δ mutant strains cannot grow on non-fermentable carbon sources and rapidly accumulate suppressor mutations, which reverse growth defects of sch9Δ mutants. sch9Δ induces gene expression of three transcription factors required for utilization of non-fermentable carbon sources, Cat8, Adr1, and Hap4, while sch9Δ suppressor mutations, termed sns1 and sns2, strongly decrease the gene expression of those transcription factors. Despite the genetic suppression interactions, both sch9Δ and sns1 (or sns2) homozygous mutants have severe defects in meiosis. By screening mutants defective in sporulation, we identified additional sch9Δ suppressor mutants with mutations in GPB1, GPB2, and MCK1. Using library complementation and genetic analysis, we identified SNS1 and SNS2 to be IRA2 and IRA1, respectively. Furthermore, we discovered that lifespan extension in sch9Δ mutants is dependent on IRA2 and that PKA inactivation greatly increases basal expression of CAT8, ADR1, and HAP4. Our results demonstrate that sch9Δ leads to complete loss of growth on non-fermentable carbon sources and mutations in MCK1 or genes encoding negative regulators of the Ras/PKA pathway reverse sch9Δ mutant phenotypes.
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Affiliation(s)
- Patricia P Peterson
- Department of Biological Sciences, University of New Orleans, New Orleans, LA 70148, USA
| | - Zhengchang Liu
- Department of Biological Sciences, University of New Orleans, New Orleans, LA 70148, USA
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13
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Topolska M, Roelants FM, Si EP, Thorner J. TORC2-Dependent Ypk1-Mediated Phosphorylation of Lam2/Ltc4 Disrupts Its Association with the β-Propeller Protein Laf1 at Endoplasmic Reticulum-Plasma Membrane Contact Sites in the Yeast Saccharomyces cerevisiae. Biomolecules 2020; 10:biom10121598. [PMID: 33255682 PMCID: PMC7760575 DOI: 10.3390/biom10121598] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Revised: 11/23/2020] [Accepted: 11/23/2020] [Indexed: 12/11/2022] Open
Abstract
Membrane-tethered sterol-binding Lam/Ltc proteins localize at junctions between the endoplasmic reticulum (ER) membrane and other organelles. Two of the six family members-Lam2/Ltc4 (initially Ysp2) and paralog Lam4/Ltc3-localize to ER-plasma membrane (PM) contact sites (CSs) and mediate retrograde ergosterol transport from the PM to the ER. Our prior work demonstrated that Lam2 and Lam4 are substrates of TORC2-regulated protein kinase Ypk1, that Ypk1-mediated phosphorylation inhibits their function in retrograde sterol transport, and that PM sterol retention bolsters cell survival under stressful conditions. At ER-PM CSs, Lam2 and Lam4 associate with Laf1/Ymr102c and Dgr2/Ykl121w (paralogous WD40 repeat-containing proteins) that reportedly bind sterol. Using fluorescent tags, we found that Lam2 and Lam4 remain at ER-PM CSs when Laf1 and Dgr2 are absent, whereas neither Laf1 nor Dgr2 remain at ER-PM CSs when Lam2 and Lam4 are absent. Loss of Laf1 (but not Dgr2) impedes retrograde ergosterol transport, and a laf1∆ mutation does not exacerbate the transport defect of lam2∆ lam4∆ cells, indicating a shared function. Lam2 and Lam4 bind Laf1 and Dgr2 in vitro in a pull-down assay, and the PH domain in Lam2 hinders its interaction with Laf1. Lam2 phosphorylated by Ypk1, and Lam2 with phosphomimetic (Glu) replacements at its Ypk1 sites, exhibited a marked reduction in Laf1 binding. Thus, phosphorylation prevents Lam2 interaction with Laf1 at ER-PM CSs, providing a mechanism by which Ypk1 action inhibits retrograde sterol transport.
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Affiliation(s)
- Magdalena Topolska
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3202, USA; (M.T.); (F.M.R.); (E.P.S.)
- Villum Center for Bioanalytical Sciences, Department of Biochemistry and Molecular Biology, University of Southern Denmark, 5000 Odense, Denmark
| | - Françoise M. Roelants
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3202, USA; (M.T.); (F.M.R.); (E.P.S.)
| | - Edward P. Si
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3202, USA; (M.T.); (F.M.R.); (E.P.S.)
- Eastern Virginia Medical School, P.O. Box 1980, Norfolk, VA 23501-1980, USA
| | - Jeremy Thorner
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3202, USA; (M.T.); (F.M.R.); (E.P.S.)
- Correspondence: ; Tel.: +1-510-642-2558; Fax: +1-510-642-6420
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