scholarly journals A conserved signaling network monitors delivery of sphingolipids to the plasma membrane in budding yeast

2017 ◽  
Author(s):  
Jesse Clarke ◽  
Noah Dephoure ◽  
Ira Horecka ◽  
Steven Gygi ◽  
Douglas Kellogg
Keyword(s):  
Cell Cycle ◽  
Plasma Membrane ◽  
Cell Growth ◽  
Membrane Trafficking ◽  
Ribosome Biogenesis ◽  
Essential Role ◽  
Budding Yeast ◽  
Control Cell ◽  
Signaling Network ◽  
Membrane Growth

AbstractIn budding yeast, cell cycle progression and ribosome biogenesis are dependent upon plasma membrane growth, which ensures that events of cell growth are coordinated with each other and with the cell cycle. However, the signals that link the cell cycle and ribosome biogenesis to membrane growth are poorly understood. Here, we used proteome-wide mass spectrometry to systematically discover signals associated with membrane growth. The results suggest that membrane trafficking events required for membrane growth generate sphingolipid-dependent signals. A conserved signaling network plays an essential role in signaling by responding to delivery of sphingolipids to the plasma membrane. In addition, sphingolipid-dependent signals control phosphorylation of protein kinase C (Pkc1), which plays an essential role in the pathways that link the cell cycle and ribosome biogenesis to membrane growth. Together, these discoveries provide new clues to how growth-dependent signals control cell growth and the cell cycle.

scholarly journals A conserved signaling network monitors delivery of sphingolipids to the plasma membrane in budding yeast

2017 ◽  
Vol 28 (20) ◽  
pp. 2589-2599 ◽  
Author(s):  
Jesse Clarke ◽  
Noah Dephoure ◽  
Ira Horecka ◽  
Steven Gygi ◽  
Douglas Kellogg
Keyword(s):  
Cell Cycle ◽  
Plasma Membrane ◽  
Cell Growth ◽  
Membrane Trafficking ◽  
Ribosome Biogenesis ◽  
Essential Role ◽  
Budding Yeast ◽  
Control Cell ◽  
Signaling Network ◽  
Membrane Growth

In budding yeast, cell cycle progression and ribosome biogenesis are dependent on plasma membrane growth, which ensures that events of cell growth are coordinated with each other and with the cell cycle. However, the signals that link the cell cycle and ribosome biogenesis to membrane growth are poorly understood. Here we used proteome-wide mass spectrometry to systematically discover signals associated with membrane growth. The results suggest that membrane trafficking events required for membrane growth generate sphingolipid-dependent signals. A conserved signaling network appears to play an essential role in signaling by responding to delivery of sphingolipids to the plasma membrane. In addition, sphingolipid-dependent signals control phosphorylation of protein kinase C (Pkc1), which plays an essential role in the pathways that link the cell cycle and ribosome biogenesis to membrane growth. Together these discoveries provide new clues as to how growth-­dependent signals control cell growth and the cell cycle.

scholarly journals Growth-dependent signals drive an increase in early G1 cyclin concentration to link cell cycle entry with cell growth

2020 ◽  
Author(s):  
Robert A. Sommer ◽  
Jerry T. DeWitt ◽  
Raymond Tan ◽  
Douglas R. Kellogg
Keyword(s):  
Cell Cycle ◽  
Cell Growth ◽  
Budding Yeast ◽  
Control Cell ◽  
Transcriptional Repressor ◽  
Cell Cycle Entry ◽  
G1 Cyclin

AbstractEntry into the cell cycle occurs only when sufficient growth has occurred. In budding yeast, the cyclin Cln3 initiates 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 play roles in control of cell growth and size. Together, the data are consistent with models in which Cln3 serves as the crucial link between the cell cycle and signals that control cell growth and size.

scholarly journals Conserved Ark1-related kinases control TORC2 signaling

2019 ◽  
Author(s):  
Maria Alcaide-Gavilán ◽  
Selene Banuelos ◽  
Rafael Lucena ◽  
Douglas R. Kellogg
Keyword(s):  
Cell Cycle ◽  
Growth Rate ◽  
Plasma Membrane ◽  
Cell Growth ◽  
Cell Size ◽  
Cell Cycle Progression ◽  
Coordinated Control ◽  
Cycle Progression ◽  
Membrane Growth ◽  
Slow Growing

AbstractIn all orders of life, cell cycle progression is dependent upon 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 (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 paralogs 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 indicates 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.

scholarly journals Dilution and titration of cell-cycle regulators may control cell size in budding yeast

2018 ◽  
Author(s):  
Frank S. Heldt ◽  
Reece Lunstone ◽  
John J. Tyson ◽  
Béla Novák
Keyword(s):  
Cell Cycle ◽  
Cell Growth ◽  
Cell Size ◽  
Cell Cycle Progression ◽  
Budding Yeast ◽  
Control Cell ◽  
Gene Copy Number ◽  
Size Control ◽  
Gene Copy ◽  
Cell Cycle Regulators

AbstractThe size of a cell sets the scale for all biochemical processes within it, thereby affecting cellular fitness and survival. Hence, cell size needs to be kept within certain limits and relatively constant over multiple generations. However, how cells measure their size and use this information to regulate growth and division remains controversial. Here, we present two mechanistic mathematical models of the budding yeast (S. cerevisiae) cell cycle to investigate competing hypotheses on size control: inhibitor dilution and titration of nuclear sites. Our results suggest that an inhibitor-dilution mechanism, in which cell growth dilutes the transcriptional inhibitor Whi5 against the constant activator Cln3, can facilitate size homeostasis. This is achieved by utilising a positive feedback loop to establish a fixed size threshold for the START transition, which efficiently couples cell growth to cell cycle progression. Yet, we show that inhibitor dilution cannot reproduce the size of mutants that alter the cell’s overall ploidy and WHI5 gene copy number. By contrast, size control through titration of Cln3 against a constant number of genomic binding sites for the transcription factor SBF recapitulates both size homeostasis and the size of these mutant strains. Moreover, this model produces an imperfect ‘sizer’ behaviour in G1 and a ‘timer’ in S/G2/M, which combine to yield an ‘adder’ over the whole cell cycle; an observation recently made in experiments. Hence, our model connects these phenomenological data with the molecular details of the cell cycle, providing a systems-level perspective of budding yeast size control.

scholarly journals Growth-dependent signals drive an increase in early G1 cyclin concentration to link cell cycle entry with cell growth

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Robert A Sommer ◽  
Jerry T DeWitt ◽  
Raymond Tan ◽  
Douglas R Kellogg
Keyword(s):  
Cell Cycle ◽  
Cell Growth ◽  
Budding Yeast ◽  
Control Cell ◽  
Transcriptional Repressor ◽  
Cell Cycle Entry ◽  
G1 Cyclin

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.

scholarly journals Specific Inhibition of Elm1 Kinase Activity Reveals Functions Required for Early G1 Events

2003 ◽  
Vol 23 (17) ◽  
pp. 6327-6337 ◽  
Author(s):  
Aparna Sreenivasan ◽  
Anthony C. Bishop ◽  
Kevan M. Shokat ◽  
Douglas R. Kellogg
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Cell Growth ◽  
Kinase Activity ◽  
Budding Yeast ◽  
Specific Inhibition ◽  
Bud Emergence ◽  
Wee1 Kinase ◽  
Yeast Homolog

ABSTRACT In budding yeast, the Elm1 kinase is required for coordination of cell growth and cell division at G2/M. Elm1 is also required for efficient cytokinesis and for regulation of Swe1, the budding yeast homolog of the Wee1 kinase. To further characterize Elm1 function, we engineered an ELM1 allele that can be rapidly and selectively inhibited in vivo. We found that inhibition of Elm1 kinase activity during G2 results in a phenotype similar to the phenotype caused by deletion of the ELM1 gene, as expected. However, inhibition of Elm1 kinase activity earlier in the cell cycle results in a prolonged G1 delay. The G1 requirement for Elm1 kinase activity occurs before bud emergence, polarization of the septins, and synthesis of G1 cyclins. Inhibition of Elm1 kinase activity during early G1 also causes defects in the organization of septins, and inhibition of Elm1 kinase activity in a strain lacking the redundant G1 cyclins CLN1 and CLN2 is lethal. These results demonstrate that the Elm1 kinase plays an important role in G1 events required for bud emergence and septin organization.

scholarly journals PP2ARts1 is a master regulator of pathways that control cell size

2014 ◽  
Vol 204 (3) ◽  
pp. 359-376 ◽  
Author(s):  
Jessica Zapata ◽  
Noah Dephoure ◽  
Tracy MacDonough ◽  
Yaxin Yu ◽  
Emily J. Parnell ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Growth ◽  
Cell Size ◽  
Control Cell ◽  
Size Control ◽  
Regulatory Subunit ◽  
Delay Cell ◽  
Cell Cycle Entry ◽  
G1 Cyclin

Cell size checkpoints ensure that passage through G1 and mitosis occurs only when sufficient growth has occurred. The mechanisms by which these checkpoints work are largely unknown. PP2A associated with the Rts1 regulatory subunit (PP2ARts1) is required for cell size control in budding yeast, but the relevant targets are unknown. In this paper, we used quantitative proteome-wide mass spectrometry to identify proteins controlled by PP2ARts1. This revealed that PP2ARts1 controls the two key checkpoint pathways thought to regulate the cell cycle in response to cell growth. To investigate the role of PP2ARts1 in these pathways, we focused on the Ace2 transcription factor, which is thought to delay cell cycle entry by repressing transcription of the G1 cyclin CLN3. Diverse experiments suggest that PP2ARts1 promotes cell cycle entry by inhibiting the repressor functions of Ace2. We hypothesize that control of Ace2 by PP2ARts1 plays a role in mechanisms that link G1 cyclin accumulation to cell growth.

scholarly journals Collapse of Ribosome Biogenesis Induces Rapid Erythroblast Differentiation

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 2671-2671
Author(s):  
Anna Raimbault ◽  
Celia Floquet ◽  
Boris Guyot ◽  
Ulku Cuhadar ◽  
Olivier Kosmider ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Differentiation ◽  
Cell Growth ◽  
Cell Size ◽  
Ribosome Biogenesis ◽  
Size Reduction ◽  
Erythroid Cell ◽  
Specific Chemical ◽  
Final Maturation ◽  
Erythroid Cell Differentiation

Abstract Genetic insults of ribosomal protein (RP) genes including heterozygous mutations in Diamond Blackfan Anemia (DBA) or RPS14 haploinsufficiency in acquired 5q- syndrome selectively impair erythropoiesis suggesting that the integrity of ribosome biogenesis (RB) is fully required for the production of 10e11erythrocytes per day in humans. Defective RB consecutive to RPL5, RPL11 mutation or RPS14 deletion is thought to induce cell cycle arrest and a various degree of apoptosis in erythroblasts (EB). However, recent data showed that, loss of RPL5/RPL11neither induces apoptosis nor arrests cell cycle, but hampers the progression through the G1 phase, in primary fibroblasts. Furthermore, RB coordinates cell cycle to cell growth for the maintenance of constant cell size. In this work, we investigate the role of RB in erythroid cell differentiation and cell size regulation. We first analyzed the renewal of ribosome during in vitro differentiation of human EB derived from cytapheresis CD34+ cells and mouse erythroblasts derived from mouse fetal liver by a pulsed SILAC (Stable Isotopic Labeling by Amino acids in Culture cell) riboproteomic assay. Ribosome biogenesis dramatically decreases with the disappearance of proEB and basophilic EB and the onset of poly- and ortho-chromatophilic EB. Importantly, inhibition of RNA polI by CX-5461 in proEB forced them to enter the final maturation steps with an increase of glycophorin A (GPA) expression. To study the effect of RPS14 heterozygous deletion on RB, UT7/EPO cell line was infected by a lentivirus containing an inducible GFP-shRNA RPS14. After a 48-h treatment with doxycyclin, Rps14 protein expression was reduced by half and sorted GFP-positive cells had an altered ribosome profile devoid of 40S small subunit or 80S entire particle. Consistently, RB inhibition induced a cell size reduction. Second, we compared RB level in cells responsive to SCF+EPO or EPO alone. RB was optimal when EB responded to SCF+EPO and this was correlated with cell size being higher in SCF+EPO-responsive cells compared to EPO-responsive cells. Both cytokines additively activate the cell growth regulator, p70S6K1. Third, inhibition of p70S6K1 by rapamycin, or a specific chemical S6K1 inhibitor significantly reduced RB as shown by a 50% decrease of ribosome renewal in pulsed-SILAC. Inhibition of RB by rapamycin led to a size reduction and to GPA acquisition, which are the features of erythroid cell differentiation. Our data shows that the collapse of RB due to the loss of c-Kit and reduced activation of p70S6K1 is a key step for cell growth inhibition and induction of terminal differentiation in human or mouse erythroblasts. Disclosures No relevant conflicts of interest to declare.

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