1
|
DeMarco AG, Dibble MG, Hall MC. Inducible degradation-coupled phosphoproteomics identifies PP2A Rts1 as a novel eisosome regulator. Front Cell Dev Biol 2024; 12:1451027. [PMID: 39234563 PMCID: PMC11371571 DOI: 10.3389/fcell.2024.1451027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2024] [Accepted: 08/02/2024] [Indexed: 09/06/2024] Open
Abstract
Introduction Reversible protein phosphorylation is an abundant post-translational modification dynamically regulated by opposing kinases and phosphatases. Protein phosphorylation has been extensively studied in cell division, where waves of cyclin-dependent kinase activity, peaking in mitosis, drive the sequential stages of the cell cycle. Here we developed and employed a strategy to specifically probe kinase or phosphatase substrates at desired times or experimental conditions in the model organism Saccharomyces cerevisiae. Methods We combined auxin-inducible degradation (AID) with mass spectrometry-based phosphoproteomics, which allowed us to arrest physiologically normal cultures in mitosis prior to rapid phosphatase degradation and phosphoproteome analysis. Results and discussion Our results revealed that protein phosphatase 2A coupled with its B56 regulatory subunit, Rts1 (PP2ARts1), is involved in dephosphorylation of numerous proteins in mitosis, highlighting the need for phosphatases to selectively maintain certain proteins in a hypophosphorylated state in the face of high mitotic kinase activity. Unexpectedly, we observed elevated phosphorylation at many sites on several subunits of the fungal eisosome complex following rapid Rts1 degradation. Eisosomes are dynamic polymeric assemblies that create furrows in the plasma membrane important in regulating nutrient import, lipid metabolism, and stress responses, among other things. We found that PP2ARts1-mediated dephosphorylation of eisosomes promotes their plasma membrane association and we provide evidence that this regulation impacts eisosome roles in metabolic homeostasis. The combination of rapid, inducible protein degradation with proteomic profiling offers several advantages over common protein disruption methods for characterizing substrates of regulatory enzymes involved in dynamic biological processes.
Collapse
Affiliation(s)
- Andrew G DeMarco
- Department of Biochemistry, Purdue University, West Lafayette, IN, United States
| | - Marcella G Dibble
- Department of Biochemistry, Purdue University, West Lafayette, IN, United States
| | - Mark C Hall
- Department of Biochemistry, Purdue University, West Lafayette, IN, United States
- Institute for Cancer Research, Purdue University, West Lafayette, IN, United States
- Institute for Drug Discovery, Purdue University, West Lafayette, IN, United States
- Institute of Inflammation, Immunology and Infectious Disease, Purdue University, West Lafayette, IN, United States
| |
Collapse
|
2
|
Talavera RA, Prichard BE, Sommer RA, Leitao RM, Sarabia CJ, Hazir S, Paulo JA, Gygi SP, Kellogg DR. Cell growth and nutrient availability control the mitotic exit signaling network in budding yeast. J Cell Biol 2024; 223:e202305008. [PMID: 38722822 PMCID: PMC11082370 DOI: 10.1083/jcb.202305008] [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: 05/07/2023] [Revised: 01/03/2024] [Accepted: 04/04/2024] [Indexed: 05/13/2024] Open
Abstract
Cell growth is required for cell cycle progression. The amount of growth required for cell cycle progression is reduced in poor nutrients, which leads to a reduction in cell size. In budding yeast, nutrients can influence cell size by modulating the extent of bud growth, which occurs predominantly in mitosis. However, the mechanisms are unknown. Here, we used mass spectrometry to identify proteins that modulate bud growth in response to nutrient availability. This led to the discovery that nutrients regulate numerous components of the mitotic exit network (MEN), which controls exit from mitosis. A key component of the MEN undergoes gradual multisite phosphorylation during bud growth that is dependent upon bud growth and correlated with the extent of growth. Furthermore, activation of the MEN is sufficient to override a growth requirement for mitotic exit. The data suggest a model in which the MEN ensures that mitotic exit occurs only when an appropriate amount of bud growth has occurred.
Collapse
Affiliation(s)
- Rafael A. Talavera
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, CA, USA
| | - Beth E. Prichard
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, CA, USA
| | - Robert A. Sommer
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, CA, USA
| | - Ricardo M. Leitao
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, CA, USA
| | - Christopher J. Sarabia
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, CA, USA
| | - Semin Hazir
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, CA, USA
| | - Joao A. Paulo
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Steven P. Gygi
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Douglas R. Kellogg
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, CA, USA
| |
Collapse
|
3
|
Brambila A, Prichard BE, DeWitt JT, Kellogg DR. Evidence for novel mechanisms that control cell-cycle entry and cell size. Mol Biol Cell 2024; 35:ar46. [PMID: 38231863 PMCID: PMC11064657 DOI: 10.1091/mbc.e23-05-0174] [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: 05/18/2023] [Revised: 01/08/2024] [Accepted: 01/10/2024] [Indexed: 01/19/2024] Open
Abstract
Entry into the cell cycle in late G1 phase occurs only when sufficient growth has occurred. In budding yeast, a cyclin called Cln3 is thought to link cell-cycle entry to cell growth. Cln3 accumulates during growth in early G1 phase and eventually helps trigger expression of late G1 phase cyclins that drive cell-cycle entry. All current models for cell-cycle entry assume that expression of late G1 phase cyclins is initiated at the transcriptional level. Current models also assume that the sole function of Cln3 in cell-cycle entry is to promote transcription of late G1 phase cyclins, and that Cln3 works solely in G1 phase. Here, we show that cell cycle-dependent expression of the late G1 phase cyclin Cln2 does not require any functions of the CLN2 promoter. Moreover, Cln3 can influence accumulation of Cln2 protein via posttranscriptional mechanisms. Finally, we show that Cln3 has functions in mitosis that strongly influence cell size. Together, these discoveries reveal the existence of surprising new mechanisms that challenge current models for control of cell-cycle entry and cell size.
Collapse
Affiliation(s)
- Amanda Brambila
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, CA 95064
| | - Beth E. Prichard
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, CA 95064
| | - Jerry T. DeWitt
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, CA 95064
| | - Douglas R. Kellogg
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, CA 95064
| |
Collapse
|
4
|
Lucena R, Jasani A, Anastasia S, Kellogg D, Alcaide-Gavilan M. Casein kinase 1 controls components of a TORC2 signaling network in budding yeast. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.30.578072. [PMID: 38352417 PMCID: PMC10862894 DOI: 10.1101/2024.01.30.578072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/24/2024]
Abstract
Tor kinases play diverse and essential roles in control of nutrient signaling and cell growth. Tor kinases are assembled into two large multiprotein complexes referred to as Tor Complex 1 and Tor Complex 2 (TORC1 and TORC2). In budding yeast, TORC2 controls a signaling network that relays signals regarding carbon source that strongly influence growth rate and cell size. However, the mechanisms that control TORC2 signaling are poorly understood. Activation of TORC2 requires Mss4, a phosphoinositol kinase that initiates assembly of a multi-protein complex at the plasma membrane that recruits and activates downstream targets of TORC2. Localization of Mss4 to the plasma membrane is controlled by phosphorylation and previous work suggested that yeast homologs of casein kinase 1γ, referred to as Yck1 and Yck2, control phosphorylation of Mss4. Here, we generated a new analog-sensitive allele of YCK2 and used it to test whether Yck1/2 influence signaling in the TORC2 network. We found that multiple components of the TORC2 network are strongly influenced by Yck1/2 signaling.
Collapse
Affiliation(s)
- Rafael Lucena
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Sawnta Cruz, CA 95064, USA
- Present address: Department of Cell Biology, School of Biology, University of Seville, 41012, Seville, Spain
| | - Akshi Jasani
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Sawnta Cruz, CA 95064, USA
| | - Steph Anastasia
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Sawnta Cruz, CA 95064, USA
- Present address: Monterey One Water, 5 Harris Ct, Monterey, CA, 93940, USA
| | - Douglas Kellogg
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Sawnta Cruz, CA 95064, USA
| | - Maria Alcaide-Gavilan
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Sawnta Cruz, CA 95064, USA
- Present address: Department of Cell Biology, School of Biology, University of Seville, 41012, Seville, Spain
| |
Collapse
|
5
|
DeMarco AG, Dibble MG, Hall MC. Inducible degradation-coupled phosphoproteomics identifies PP2A Rts1 as a novel eisosome regulator. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.24.563668. [PMID: 37961087 PMCID: PMC10634780 DOI: 10.1101/2023.10.24.563668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
Reversible protein phosphorylation is an abundant post-translational modification dynamically regulated by opposing kinases and phosphatases. Protein phosphorylation has been extensively studied in cell division, where waves of cyclin-dependent kinase activity, peaking in mitosis, drive the sequential stages of the cell cycle. Here we developed and employed a strategy to specifically probe kinase or phosphatase substrates at desired times or experimental conditions in the model organism Saccharomyces cerevisiae. We combined auxin-inducible degradation (AID) with mass spectrometry-based phosphoproteomics, which allowed us to arrest physiologically normal cultures in mitosis prior to rapid phosphatase degradation and phosphoproteome analysis. Our results revealed that protein phosphatase 2A coupled with its B56 regulatory subunit, Rts1 (PP2ARts1), is involved in dephosphorylation of numerous proteins in mitosis, highlighting the need for phosphatases to selectively maintain certain proteins in a hypophosphorylated state in the face of high mitotic kinase activity. Unexpectedly, we observed elevated phosphorylation at many sites on several subunits of the fungal eisosome complex following rapid Rts1 degradation. Eisosomes are dynamic polymeric assemblies that create furrows in the plasma membrane important in regulating nutrient import, lipid metabolism, and stress responses, among other things. We found that PP2ARts1-mediated dephosphorylation of eisosomes promotes their plasma membrane association and we provide evidence that this regulation impacts eisosome roles in metabolic homeostasis. The combination of rapid, inducible protein degradation with proteomic profiling offers several advantages over common protein disruption methods for characterizing substrates of regulatory enzymes involved in dynamic biological processes.
Collapse
Affiliation(s)
- Andrew G. DeMarco
- Department of Biochemistry, Purdue University, West Lafayette, IN, 47907
| | - Marcella G. Dibble
- Department of Biochemistry, Purdue University, West Lafayette, IN, 47907
| | - Mark C. Hall
- Department of Biochemistry, Purdue University, West Lafayette, IN, 47907
- Institute for Cancer Research, Purdue University, West Lafayette, IN, 47907
| |
Collapse
|
6
|
Kellogg DR, Levin PA. Nutrient availability as an arbiter of cell size. Trends Cell Biol 2022; 32:908-919. [PMID: 35851491 PMCID: PMC9588502 DOI: 10.1016/j.tcb.2022.06.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 06/07/2022] [Accepted: 06/16/2022] [Indexed: 01/21/2023]
Abstract
Pioneering work carried out over 60 years ago discovered that bacterial cell size is proportional to the growth rate set by nutrient availability. This relationship is traditionally referred to as the 'growth law'. Subsequent studies revealed the growth law to hold across all orders of life, a remarkable degree of conservation. However, recent work suggests the relationship between growth rate, nutrients, and cell size is far more complicated and less deterministic than originally thought. Focusing on bacteria and yeast, here we review efforts to understand the molecular mechanisms underlying the relationship between growth rate and cell size.
Collapse
Affiliation(s)
- Douglas R Kellogg
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064, USA.
| | - Petra Anne Levin
- Department of Biology, Washington University in St. Louis, St Louis, MO 63130, USA; Center for Science & Engineering of Living Systems (CSELS), McKelvey School of Engineering, Washington University in St Louis, St Louis, MO 63130, USA.
| |
Collapse
|
7
|
Hollenstein DM, Veis J, Romanov N, Gérecová G, Ogris E, Hartl M, Ammerer G, Reiter W. PP2A Rts1 antagonizes Rck2-mediated hyperosmotic stress signaling in yeast. Microbiol Res 2022; 260:127031. [PMID: 35461031 DOI: 10.1016/j.micres.2022.127031] [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: 09/17/2021] [Revised: 04/03/2022] [Accepted: 04/05/2022] [Indexed: 11/21/2022]
Abstract
In Saccharomyces cerevisiae, impairment of protein phosphatase PP2ARts1 leads to temperature and hyperosmotic stress sensitivity, yet the underlying mechanism and the scope of action of the phosphatase in the stress response remain elusive. Using a quantitative mass spectrometry-based approach we have identified a set of putative substrate proteins that show both hyperosmotic stress- and PP2ARts1-dependent changes in their phosphorylation pattern. A comparative analysis with published MS-shotgun data revealed that the phosphorylation status of many of these sites is regulated by the MAPKAP kinase Rck2, suggesting that the phosphatase antagonizes Rck2 signaling. Detailed gel mobility shift assays and protein-protein interaction analysis strongly indicate that Rck2 activity is directly regulated by PP2ARts1 via a SLiM B56-family interaction motif, revealing how PP2ARts1 influences the response to hyperosmotic stress in Yeast.
Collapse
Affiliation(s)
- D M Hollenstein
- Department of Biochemistry and Cell Biology, Max Perutz Labs, University of Vienna, Vienna BioCenter, Dr. Bohr-Gasse 9, 1030 Vienna, Austria
| | - J Veis
- Department of Biochemistry and Cell Biology, Max Perutz Labs, University of Vienna, Vienna BioCenter, Dr. Bohr-Gasse 9, 1030 Vienna, Austria; Center for Medical Biochemistry, Max Perutz Labs, Medical University of Vienna, Vienna BioCenter, Dr. Bohr-Gasse 9, 1030 Vienna, Austria
| | - N Romanov
- Max Planck Institute of Biophysics, Max-von-Laue Straße 3, 60438 Frankfurt am Main, Germany
| | - G Gérecová
- Department of Biochemistry and Cell Biology, Max Perutz Labs, University of Vienna, Vienna BioCenter, Dr. Bohr-Gasse 9, 1030 Vienna, Austria
| | - E Ogris
- Center for Medical Biochemistry, Max Perutz Labs, Medical University of Vienna, Vienna BioCenter, Dr. Bohr-Gasse 9, 1030 Vienna, Austria
| | - M Hartl
- Mass Spectrometry Facility, Max Perutz Labs, University of Vienna, Vienna BioCenter, Dr. Bohr-Gasse 9, 1030 Vienna, Austria
| | - G Ammerer
- Department of Biochemistry and Cell Biology, Max Perutz Labs, University of Vienna, Vienna BioCenter, Dr. Bohr-Gasse 9, 1030 Vienna, Austria
| | - W Reiter
- Department of Biochemistry and Cell Biology, Max Perutz Labs, University of Vienna, Vienna BioCenter, Dr. Bohr-Gasse 9, 1030 Vienna, Austria; Mass Spectrometry Facility, Max Perutz Labs, University of Vienna, Vienna BioCenter, Dr. Bohr-Gasse 9, 1030 Vienna, Austria.
| |
Collapse
|
8
|
Wang L, Yang X, Jiang HY, Song ZM, Lin X, Hu XP, Li CF. Protein kinases Elm1 and Sak1 of Saccharomyces cerevisiae exerted different functions under high-glucose and heat shock stresses. Appl Microbiol Biotechnol 2022; 106:2029-2042. [PMID: 35194654 DOI: 10.1007/s00253-022-11840-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 02/10/2022] [Accepted: 02/14/2022] [Indexed: 11/02/2022]
Abstract
Phosphorylation catalyzed by protein kinases is the most common and important regulatory pathway in the adaptive physiological responses to the changes in nutrition and environment of yeast. This study focused on the functions of Elm1, Sak1, and Tos3, which are three upstream protein kinases of Snf1 in Saccharomyces cerevisiae, in response to high-glucose and heat shock stresses. Results suggested that changing the gene dosage of ELM1/SAK1/TOS3 had different effects under high-glucose and heat shock stresses. ELM1 and SAK1 overexpressions could enhance the tolerance of S. cerevisiae to high-glucose and heat shock stresses, respectively. Nevertheless, the overexpression of TOS3 decreased the tolerance to high-glucose stress, and a native level of Tos3 was important for the normal adaptation to heat shock condition. The overexpression of ELM1 increased the accumulation of trehalose and ergosterol and altered the composition of fatty acids with altered gene expressions involved in the metabolism of three metabolites. Enhanced resistance to heat shock stress in SAK1 overexpression might be related to the enhanced accumulation of trehalose and ergosterol and upregulated transcription of genes related to the metabolism of trehalose and ergosterol. Furthermore, Elm1 might regulate the metabolism of trehalose, ergosterol, and fatty acids in a Snf1-independent form under high-glucose stress. A Snf1-independent pathway might be involved in the regulation of trehalose metabolism by Sak1 under heat shock condition. However, Sak1 and Snf1 may have an indirect relationship in the regulation of ergosterol synthesis. KEY POINTS: • Altering the gene dosage of ELM1/SAK1/TOS3 had different effects on stress responses • Elm1 regulated high-glucose response in a Snf1-independent manner • Sak1 and Snf1 had an indirect relationship in the regulation of heat shock response.
Collapse
Affiliation(s)
- Lu Wang
- College of Food Science and Engineering, Hainan University, Haikou, 570228, People's Republic of China
| | - Xu Yang
- College of Food Science and Engineering, Hainan University, Haikou, 570228, People's Republic of China
| | - Huan-Yuan Jiang
- College of Food Science and Engineering, Hainan University, Haikou, 570228, People's Republic of China
| | - Ze-Ming Song
- College of Food Science and Engineering, Hainan University, Haikou, 570228, People's Republic of China
| | - Xue Lin
- College of Food Science and Engineering, Hainan University, Haikou, 570228, People's Republic of China. .,Engineering Research Center of Utilization of Tropical Polysaccharide Resources, Ministry of Education, Haikou, 570228, People's Republic of China. .,Hainan Key Laboratory of Food Nutrition and Functional Food, Haikou, 570228, People's Republic of China.
| | - Xiao-Ping Hu
- College of Food Science and Engineering, Hainan University, Haikou, 570228, People's Republic of China. .,Engineering Research Center of Utilization of Tropical Polysaccharide Resources, Ministry of Education, Haikou, 570228, People's Republic of China. .,Hainan Key Laboratory of Food Nutrition and Functional Food, Haikou, 570228, People's Republic of China.
| | - Cong-Fa Li
- College of Food Science and Engineering, Hainan University, Haikou, 570228, People's Republic of China.,Engineering Research Center of Utilization of Tropical Polysaccharide Resources, Ministry of Education, Haikou, 570228, People's Republic of China.,Hainan Key Laboratory of Food Nutrition and Functional Food, Haikou, 570228, People's Republic of China
| |
Collapse
|
9
|
Sommer RA, DeWitt JT, Tan R, Kellogg DR. Growth-dependent signals drive an increase in early G1 cyclin concentration to link cell cycle entry with cell growth. eLife 2021; 10:64364. [PMID: 34713806 PMCID: PMC8592568 DOI: 10.7554/elife.64364] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Accepted: 10/29/2021] [Indexed: 01/13/2023] Open
Abstract
Entry into the cell cycle occurs only when sufficient growth has occurred. In budding yeast, the cyclin Cln3 is thought to initiate cell cycle entry by inactivating a transcriptional repressor called Whi5. Growth-dependent changes in the concentrations of Cln3 or Whi5 have been proposed to link cell cycle entry to cell growth. However, there are conflicting reports regarding the behavior and roles of Cln3 and Whi5. Here, we found no evidence that changes in the concentration of Whi5 play a major role in controlling cell cycle entry. Rather, the data suggest that cell growth triggers cell cycle entry by driving an increase in the concentration of Cln3. We further found that accumulation of Cln3 is dependent upon homologs of mammalian SGK kinases that control cell growth and size. Together, the data are consistent with models in which Cln3 is a crucial link between cell growth and the cell cycle.
Collapse
Affiliation(s)
- Robert A Sommer
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, United States
| | - Jerry T DeWitt
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, United States
| | - Raymond Tan
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, United States
| | - Douglas R Kellogg
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, United States
| |
Collapse
|
10
|
Alcaide-Gavilán M, Lucena R, Banuelos S, Kellogg DR. Conserved Ark1-related kinases function in a TORC2 signaling network. Mol Biol Cell 2020; 31:2057-2069. [PMID: 32614710 PMCID: PMC7543068 DOI: 10.1091/mbc.e19-12-0685] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
In all orders of life, cell cycle progression in proliferating cells is dependent on cell growth, and the extent of growth required for cell cycle progression is proportional to growth rate. Thus, cells growing rapidly in rich nutrients are substantially larger than slow-growing cells. In budding yeast, a conserved signaling network surrounding Tor complex 2 (target of rapamycin complex 2; TORC2) controls growth rate and cell size in response to nutrient availability. Here, a search for new components of the TORC2 network identified a pair of redundant kinase paralogues called Ark1 and Prk1. Previous studies found that Ark/Prk play roles in endocytosis. Here, we show that Ark/Prk are embedded in the TORC2 network, where they appear to influence TORC2 signaling independently of their roles in endocytosis. We also show that reduced endocytosis leads to increased cell size, which suggests that cell size homeostasis requires coordinated control of plasma membrane growth and endocytosis. The discovery that Ark/Prk are embedded in the TORC2 network suggests a model in which TORC2-dependent signals control both plasma membrane growth and endocytosis, which would ensure that the rates of each process are matched to each other and to the availability of nutrients so that cells achieve and maintain an appropriate size.
Collapse
Affiliation(s)
- Maria Alcaide-Gavilán
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064
| | - Rafael Lucena
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064
| | - Selene Banuelos
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064
| | - Douglas R Kellogg
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064
| |
Collapse
|
11
|
Growth-Dependent Activation of Protein Kinases Suggests a Mechanism for Measuring Cell Growth. Genetics 2020; 215:729-746. [PMID: 32461268 DOI: 10.1534/genetics.120.303200] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Accepted: 05/17/2020] [Indexed: 11/18/2022] Open
Abstract
In all cells, progression through the cell cycle occurs only when sufficient growth has occurred. Thus, cells must translate growth into a proportional signal that can be used to measure and transmit information about growth. Previous genetic studies in budding yeast suggested that related kinases called Gin4 and Hsl1 could function in mechanisms that measure bud growth; however, interpretation of the data was complicated by the use of gene deletions that cause complex terminal phenotypes. Here, we used the first conditional alleles of Gin4 and Hsl1 to more precisely define their functions. We show that excessive bud growth during a prolonged mitotic delay is an immediate consequence of inactivating Gin4 and Hsl1 Thus, acute loss of Gin4 and Hsl1 causes cells to behave as though they cannot detect that bud growth has occurred. We further show that Gin4 and Hsl1 undergo gradual hyperphosphorylation during bud growth that is dependent upon growth and correlated with the extent of growth. Moreover, gradual hyperphosphorylation of Gin4 during bud growth requires binding to anionic phospholipids that are delivered to the growing bud. While alternative models are possible, the data suggest that signaling lipids delivered to the growing bud generate a growth-dependent signal that could be used to measure bud growth.
Collapse
|
12
|
Riggi M, Kusmider B, Loewith R. The flipside of the TOR coin - TORC2 and plasma membrane homeostasis at a glance. J Cell Sci 2020; 133:133/9/jcs242040. [PMID: 32393676 DOI: 10.1242/jcs.242040] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Target of rapamycin (TOR) is a serine/threonine protein kinase conserved in most eukaryote organisms. TOR assembles into two multiprotein complexes (TORC1 and TORC2), which function as regulators of cellular growth and homeostasis by serving as direct transducers of extracellular biotic and abiotic signals, and, through their participation in intrinsic feedback loops, respectively. TORC1, the better-studied complex, is mainly involved in cell volume homeostasis through regulating accumulation of proteins and other macromolecules, while the functions of the lesser-studied TORC2 are only now starting to emerge. In this Cell Science at a Glance article and accompanying poster, we aim to highlight recent advances in our understanding of TORC2 signalling, particularly those derived from studies in yeast wherein TORC2 has emerged as a major regulator of cell surface homeostasis.
Collapse
Affiliation(s)
- Margot Riggi
- Swiss National Centre for Competence in Research Program Chemical Biology, Geneva, Switzerland.,Department of Biochemistry, University of Geneva, Geneva, Switzerland.,Department of Molecular Biology, University of Geneva, Geneva, Switzerland
| | - Beata Kusmider
- Swiss National Centre for Competence in Research Program Chemical Biology, Geneva, Switzerland.,Department of Molecular Biology, University of Geneva, Geneva, Switzerland
| | - Robbie Loewith
- Swiss National Centre for Competence in Research Program Chemical Biology, Geneva, Switzerland .,Department of Molecular Biology, University of Geneva, Geneva, Switzerland
| |
Collapse
|
13
|
Leitao RM, Jasani A, Talavara RA, Pham A, Okobi QJ, Kellogg DR. A Conserved PP2A Regulatory Subunit Enforces Proportional Relationships Between Cell Size and Growth Rate. Genetics 2019; 213:517-528. [PMID: 31488515 PMCID: PMC6781898 DOI: 10.1534/genetics.119.301012] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Accepted: 08/10/2019] [Indexed: 11/18/2022] Open
Abstract
Cell size is proportional to growth rate. Thus, cells growing rapidly in rich nutrients can be nearly twice the size of cells growing slowly in poor nutrients. This proportional relationship appears to hold across all orders of life, yet the underlying mechanisms are unknown. In budding yeast, most growth occurs during mitosis, and the proportional relationship between cell size and growth rate is therefore enforced primarily by modulating growth in mitosis. When growth is slow, the duration of mitosis is increased to allow more time for growth, yet the amount of growth required to complete mitosis is reduced, which leads to the birth of small daughter cells. Previous studies have found that Rts1, a member of the conserved B56 family of protein phosphatase 2A regulatory subunits, works in a TORC2 signaling network that influences cell size and growth rate. However, it was unclear whether Rts1 influences cell growth and size in mitosis. Here, we show that Rts1 is required for the proportional relationship between cell size and growth rate during mitosis. Moreover, nutrients and Rts1 influence the duration and extent of growth in mitosis via Wee1 and Pds1/securin, two conserved regulators of mitotic progression. Together, the data are consistent with a model in which global signals that set growth rate also set the critical amount of growth required for cell cycle progression, which would provide a simple mechanistic explanation for the proportional relationship between cell size and growth rate.
Collapse
Affiliation(s)
- Ricardo M Leitao
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, California 95064
| | - Akshi Jasani
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, California 95064
| | - Rafael A Talavara
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, California 95064
| | - Annie Pham
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, California 95064
| | - Quincy J Okobi
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, California 95064
| | - Douglas R Kellogg
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, California 95064
| |
Collapse
|
14
|
Hua H, Kong Q, Zhang H, Wang J, Luo T, Jiang Y. Targeting mTOR for cancer therapy. J Hematol Oncol 2019; 12:71. [PMID: 31277692 PMCID: PMC6612215 DOI: 10.1186/s13045-019-0754-1] [Citation(s) in RCA: 535] [Impact Index Per Article: 107.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Accepted: 06/14/2019] [Indexed: 02/05/2023] Open
Abstract
Mechanistic target of rapamycin (mTOR) is a protein kinase regulating cell growth, survival, metabolism, and immunity. mTOR is usually assembled into several complexes such as mTOR complex 1/2 (mTORC1/2). In cooperation with raptor, rictor, LST8, and mSin1, key components in mTORC1 or mTORC2, mTOR catalyzes the phosphorylation of multiple targets such as ribosomal protein S6 kinase β-1 (S6K1), eukaryotic translation initiation factor 4E binding protein 1 (4E-BP1), Akt, protein kinase C (PKC), and type-I insulin-like growth factor receptor (IGF-IR), thereby regulating protein synthesis, nutrients metabolism, growth factor signaling, cell growth, and migration. Activation of mTOR promotes tumor growth and metastasis. Many mTOR inhibitors have been developed to treat cancer. While some of the mTOR inhibitors have been approved to treat human cancer, more mTOR inhibitors are being evaluated in clinical trials. Here, we update recent advances in exploring mTOR signaling and the development of mTOR inhibitors for cancer therapy. In addition, we discuss the mechanisms underlying the resistance to mTOR inhibitors in cancer cells.
Collapse
Affiliation(s)
- Hui Hua
- State Key Laboratory of Biotherapy, Laboratory of Stem Cell Biology, National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University, Chengdu, 610041, China
| | - Qingbin Kong
- Laboratory of Oncogene, Cancer Center, West China Hospital, Sichuan University, Chengdu, China
| | - Hongying Zhang
- Laboratory of Oncogene, Cancer Center, West China Hospital, Sichuan University, Chengdu, China
| | - Jiao Wang
- School of Basic Medicine, Chengdu University of Traditional Chinese Medicine, Chengdu, China
| | - Ting Luo
- Cancer Center, West China Hospital, Sichuan University, Chengdu, China
| | - Yangfu Jiang
- Laboratory of Oncogene, Cancer Center, West China Hospital, Sichuan University, Chengdu, China.
| |
Collapse
|