scholarly journals Competition in the chaperone-client network subordinates cell-cycle entry to growth and stress

2019 ◽  
Vol 2 (2) ◽  
pp. e201800277 ◽  
Author(s):  
David F Moreno ◽  
Eva Parisi ◽  
Galal Yahya ◽  
Federico Vaggi ◽  
Attila Csikász-Nagy ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Growth Rate ◽  
Mammalian Cells ◽  
Molecular Mechanisms ◽  
Growth Potential ◽  
Nuclear Accumulation ◽  
Single Cell Level ◽  
Cell Level ◽  
Cell Cycle Entry ◽  
Biosynthetic Machinery

The precise coordination of growth and proliferation has a universal prevalence in cell homeostasis. As a prominent property, cell size is modulated by the coordination between these processes in bacterial, yeast, and mammalian cells, but the underlying molecular mechanisms are largely unknown. Here, we show that multifunctional chaperone systems play a concerted and limiting role in cell-cycle entry, specifically driving nuclear accumulation of the G1 Cdk–cyclin complex. Based on these findings, we establish and test a molecular competition model that recapitulates cell-cycle-entry dependence on growth rate. As key predictions at a single-cell level, we show that availability of the Ydj1 chaperone and nuclear accumulation of the G1 cyclin Cln3 are inversely dependent on growth rate and readily respond to changes in protein synthesis and stress conditions that alter protein folding requirements. Thus, chaperone workload would subordinate Start to the biosynthetic machinery and dynamically adjust proliferation to the growth potential of the cell.

scholarly journals The chaperone-client network subordinates cell-cycle entry to growth and stress

2018 ◽  
Author(s):  
David F Moreno ◽  
Eva Parisi ◽  
Galal Yahya ◽  
Federico Vaggi ◽  
Attila Csikasz-Nagy ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Growth Rate ◽  
Mammalian Cells ◽  
Molecular Mechanisms ◽  
Growth Potential ◽  
Nuclear Accumulation ◽  
Single Cell Level ◽  
Cell Level ◽  
Cell Cycle Entry ◽  
Biosynthetic Machinery

The precise coordination of growth and proliferation has a universal prevalence in cell homeostasis. As a prominent property, cell size is modulated by the coordination between these processes in bacterial, yeast and mammalian cells, but the underlying molecular mechanisms are largely unknown. Here we show that multifunctional chaperone systems play a concerted and limiting role in cell-cycle entry, specifically driving nuclear accumulation of the G1 Cdk-cyclin complex. Based on these findings, we establish and test a molecular competition model that recapitulates cell-cycle-entry dependence on growth rate. As key predictions at a single-cell level, we show that availability of the Ydj1 chaperone and nuclear accumulation of the G1 cyclin Cln3 are inversely dependent on growth rate and readily respond to changes in protein synthesis and stress conditions that alter protein folding requirements. Thus, chaperone workload would subordinate Start to the biosynthetic machinery and dynamically adjust proliferation to the growth potential of the cell.

scholarly journals Single-cell transcriptomic analysis elucidates APOE genotype specific changes across cell types in two brain regions in Alzheimer’s disease

2021 ◽  
Author(s):  
Stella Belonwu ◽  
Yaqiao Li ◽  
Daniel Bunis ◽  
Arjun Arkal Rao ◽  
Caroline Warly Solsberg ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Single Cell ◽  
Molecular Mechanisms ◽  
Apoe Genotype ◽  
Cell Types ◽  
Brain Regions ◽  
Single Cell Level ◽  
Cell Level ◽  
Single Nucleus

Abstract Alzheimer’s Disease (AD) is a complex neurodegenerative disease that gravely affects patients and imposes an immense burden on caregivers. Apolipoprotein E4 (APOE4) has been identified as the most common genetic risk factor for AD, yet the molecular mechanisms connecting APOE4 to AD are not well understood. Past transcriptomic analyses in AD have revealed APOE genotype-specific transcriptomic differences; however, these differences have not been explored at a single-cell level. Here, we leverage the first two single-nucleus RNA sequencing AD datasets from human brain samples, including nearly 55,000 cells from the prefrontal and entorhinal cortices. We observed more global transcriptomic changes in APOE4 positive AD cells and identified differences across APOE genotypes primarily in glial cell types. Our findings highlight the differential transcriptomic perturbations of APOE isoforms at a single-cell level in AD pathogenesis and have implications for precision medicine development in the diagnosis and treatment of AD.

scholarly journals Cell growth dilutes the cell cycle inhibitor Rb to trigger cell division

2018 ◽  
Author(s):  
Evgeny Zatulovskiy ◽  
Daniel F. Berenson ◽  
Benjamin R. Topacio ◽  
Jan M. Skotheim
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Cell Growth ◽  
Cell Size ◽  
Mammalian Cells ◽  
Molecular Mechanisms ◽  
Inverse Correlation ◽  
Cell Types ◽  
Similar Amount ◽  
Cell Cycle Inhibitor

Cell size is fundamental to function in different cell types across the human body because it sets the scale of organelle structures, biosynthesis, and surface transport1,2. Tiny erythrocytes squeeze through capillaries to transport oxygen, while the million-fold larger oocyte divides without growth to form the ~100 cell pre-implantation embryo. Despite the vast size range across cell types, cells of a given type are typically uniform in size likely because cells are able to accurately couple cell growth to division3–6. While some genes whose disruption in mammalian cells affects cell size have been identified, the molecular mechanisms through which cell growth drives cell division have remained elusive7–12. Here, we show that cell growth acts to dilute the cell cycle inhibitor Rb to drive cell cycle progression from G1 to S phase in human cells. In contrast, other G1/S regulators remained at nearly constant concentration. Rb is a stable protein that is synthesized during S and G2 phases in an amount that is independent of cell size. Equal partitioning to daughter cells of chromatin bound Rb then ensures that all cells at birth inherit a similar amount of Rb protein. RB overexpression increased cell size in tissue culture and a mouse cancer model, while RB deletion decreased cell size and removed the inverse correlation between cell size at birth and the duration of G1 phase. Thus, Rb-dilution by cell growth in G1 provides a long-sought cell autonomous molecular mechanism for cell size homeostasis.

scholarly journals A quantitative FastFUCCI assay defines cell cycle dynamics at a single-cell level

2016 ◽  
Vol 130 (2) ◽  
pp. 512-520 ◽  
Author(s):  
Siang-Boon Koh ◽  
Patrice Mascalchi ◽  
Esther Rodriguez ◽  
Yao Lin ◽  
Duncan I. Jodrell ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Single Cell ◽  
Single Cell Level ◽  
Cell Level ◽  
Cell Cycle Dynamics

scholarly journals Heteroresistance at the Single-Cell Level: Adapting to Antibiotic Stress through a Population-Based Strategy and Growth-Controlled Interphenotypic Coordination

mBio ◽  
2014 ◽  
Vol 5 (1) ◽  
Author(s):  
Xiaorong Wang ◽  
Yu Kang ◽  
Chunxiong Luo ◽  
Tong Zhao ◽  
Lin Liu ◽  
...  
Keyword(s):  
Growth Rate ◽  
Single Cell ◽  
Task Allocation ◽  
Bacterial Population ◽  
Population Based ◽  
Phenotypic Heterogeneity ◽  
Single Cell Level ◽  
Bacterial Survival ◽  
Cell Level ◽  
Resistant Cells

ABSTRACT Heteroresistance refers to phenotypic heterogeneity of microbial clonal populations under antibiotic stress, and it has been thought to be an allocation of a subset of “resistant” cells for surviving in higher concentrations of antibiotic. The assumption fits the so-called bet-hedging strategy, where a bacterial population “hedges” its “bet” on different phenotypes to be selected by unpredicted environment stresses. To test this hypothesis, we constructed a heteroresistance model by introducing a bla CTX-M-14 gene (coding for a cephalosporin hydrolase) into a sensitive Escherichia coli strain. We confirmed heteroresistance in this clone and that a subset of the cells expressed more hydrolase and formed more colonies in the presence of ceftriaxone (exhibited stronger “resistance”). However, subsequent single-cell-level investigation by using a microfluidic device showed that a subset of cells with a distinguishable phenotype of slowed growth and intensified hydrolase expression emerged, and they were not positively selected but increased their proportion in the population with ascending antibiotic concentrations. Therefore, heteroresistance—the gradually decreased colony-forming capability in the presence of antibiotic—was a result of a decreased growth rate rather than of selection for resistant cells. Using a mock strain without the resistance gene, we further demonstrated the existence of two nested growth-centric feedback loops that control the expression of the hydrolase and maximize population growth in various antibiotic concentrations. In conclusion, phenotypic heterogeneity is a population-based strategy beneficial for bacterial survival and propagation through task allocation and interphenotypic collaboration, and the growth rate provides a critical control for the expression of stress-related genes and an essential mechanism in responding to environmental stresses. IMPORTANCE Heteroresistance is essentially phenotypic heterogeneity, where a population-based strategy is thought to be at work, being assumed to be variable cell-to-cell resistance to be selected under antibiotic stress. Exact mechanisms of heteroresistance and its roles in adaptation to antibiotic stress have yet to be fully understood at the molecular and single-cell levels. In our study, we have not been able to detect any apparent subset of “resistant” cells selected by antibiotics; on the contrary, cell populations differentiate into phenotypic subsets with variable growth statuses and hydrolase expression. The growth rate appears to be sensitive to stress intensity and plays a key role in controlling hydrolase expression at both the bulk population and single-cell levels. We have shown here, for the first time, that phenotypic heterogeneity can be beneficial to a growing bacterial population through task allocation and interphenotypic collaboration other than partitioning cells into different categories of selective advantage.

scholarly journals Computationally enhanced quantitative phase microscopy reveals autonomous oscillations in mammalian cell growth

2020 ◽  
Vol 117 (44) ◽  
pp. 27388-27399
Author(s):  
Xili Liu ◽  
Seungeun Oh ◽  
Leonid Peshkin ◽  
Marc W. Kirschner
Keyword(s):  
Cell Cycle ◽  
Growth Rate ◽  
Cell Growth ◽  
Mammalian Cells ◽  
Cell Cycle Progression ◽  
Cell Tracking ◽  
Fundamental Property ◽  
Quantitative Phase ◽  
Phase Microscopy ◽  
Quantitative Phase Microscopy

The fine balance of growth and division is a fundamental property of the physiology of cells, and one of the least understood. Its study has been thwarted by difficulties in the accurate measurement of cell size and the even greater challenges of measuring growth of a single cell over time. We address these limitations by demonstrating a computationally enhanced methodology for quantitative phase microscopy for adherent cells, using improved image processing algorithms and automated cell-tracking software. Accuracy has been improved more than twofold and this improvement is sufficient to establish the dynamics of cell growth and adherence to simple growth laws. It is also sufficient to reveal unknown features of cell growth, previously unmeasurable. With these methodological and analytical improvements, in several cell lines we document a remarkable oscillation in growth rate, occurring throughout the cell cycle, coupled to cell division or birth yet independent of cell cycle progression. We expect that further exploration with this advanced tool will provide a better understanding of growth rate regulation in mammalian cells.

scholarly journals IGF-1/IGF-1R/FAK/YAP Transduction Signaling Prompts Growth Effects in Triple-Negative Breast Cancer (TNBC) Cells

Cells ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 1010 ◽  
Author(s):  
Damiano Cosimo Rigiracciolo ◽  
Nijiro Nohata ◽  
Rosamaria Lappano ◽  
Francesca Cirillo ◽  
Marianna Talia ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Triple Negative Breast Cancer ◽  
Molecular Mechanisms ◽  
Target Genes ◽  
Triple Negative ◽  
Cancer Genomics ◽  
Treatment Options ◽  
Signal Transduction Pathway ◽  
Growth Potential ◽  
Nuclear Accumulation

Triple-negative breast cancer (TNBC) is an aggressive breast tumor subtype that currently lacks targeted treatment options. The role played by the insulin-like growth factor-1 (IGF-1) and its cognate receptor IGF-1R in TNBC has been reported. Nevertheless, the molecular mechanisms by which the IGF-1/IGF-1R system may contribute to TNBC progression still remains to be fully understood. By computational analysis of the vast cancer genomics information in public databases (TCGA and METABRIC), we obtained evidence that high IGF-1 or IGF-1R levels correlate with a worse clinical outcome in TNBC patients. Further bioinformatics analysis revealed that both the focal adhesion and the Hippo pathways are enriched in TNBC harboring an elevated expression of IGF-1 or IGF-1R. Mechanistically, we found that in TNBC cells, the IGF-1/IGF-1R system promotes the activation of the FAK signal transduction pathway, which in turn regulates the nuclear accumulation of YAP (yes-associated protein/yes-related protein) and the expression of its target genes. At the biological level, we found that the IGF-1/IGF-1R-FAK-YAP network cascade triggers the growth potential of TNBC cells, as evaluated in different experimental systems. Overall, our results suggest that the IGF-1/IGF-1R/FAK/YAP axis may contribute to the progression of the aggressive TNBC subtype.

scholarly journals Cell Cycle-Dependent Flagellar Disassembly in a Firebug Trypanosomatid Leptomonas pyrrhocoris

mBio ◽  
2019 ◽  
Vol 10 (6) ◽  
Author(s):  
Cynthia Y. He ◽  
Adarsh Singh ◽  
Vyacheslav Yurchenko
Keyword(s):  
Cell Cycle ◽  
Growth Rate ◽  
Mammalian Cells ◽  
Current Understanding ◽  
Model Organisms ◽  
Regulation Mechanism ◽  
Length Variation ◽  
Content Type ◽  
Length Regulation ◽  
Cycle Dependent

ABSTRACT Current understanding of flagellum/cilium length regulation focuses on a few model organisms with flagella of uniform length. Leptomonas pyrrhocoris is a monoxenous trypanosomatid parasite of firebugs. When cultivated in vitro, L. pyrrhocoris duplicates every 4.2 ± 0.2 h, representing the shortest doubling time reported for trypanosomatids so far. Each L. pyrrhocoris cell starts its cell cycle with a single flagellum. A new flagellum is assembled de novo, while the old flagellum persists throughout the cell cycle. The flagella in an asynchronous L. pyrrhocoris population exhibited a vast length variation of ∼3 to 24 μm, casting doubt on the presence of a length regulation mechanism based on a single balance point between the assembly and disassembly rate in these cells. Through imaging of live L. pyrrhocoris cells, a rapid, partial disassembly of the existing, old flagellum is observed upon, if not prior to, the initial assembly of a new flagellum. Mathematical modeling demonstrated an inverse correlation between the flagellar growth rate and flagellar length and inferred the presence of distinct, cell cycle-dependent disassembly mechanisms with different rates. On the basis of these observations, we proposed a min-max model that could account for the vast flagellar length range observed for asynchronous L. pyrrhocoris. This model may also apply to other flagellated organisms with flagellar length variation. IMPORTANCE Current understanding of flagellum biogenesis during the cell cycle in trypanosomatids is limited to a few pathogenic species, including Trypanosoma brucei, Trypanosoma cruzi, and Leishmania spp. The most notable characteristics of trypanosomatid flagella studied so far are the extreme stability and lack of ciliary disassembly/absorption during the cell cycle. This is different from cilia in Chlamydomonas and mammalian cells, which undergo complete absorption prior to cell cycle initiation. In this study, we examined flagellum duplication during the cell cycle of Leptomonas pyrrhocoris. With the shortest duplication time documented for all Trypanosomatidae and its amenability to culture on agarose gel with limited mobility, we were able to image these cells through the cell cycle. Rapid, cell cycle-specific flagellum disassembly different from turnover was observed for the first time in trypanosomatids. Given the observed length-dependent growth rate and the presence of different disassembly mechanisms, we proposed a min-max model that can account for the flagellar length variation observed in L. pyrrhocoris.

Molecular Mechanisms of Spindle Checkpoint-Apoptosis Linkage and Karyotypic Stability in Stem Cells.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 3361-3361
Author(s):  
Charlie Mantel ◽  
Sara Rhorabough ◽  
Ying Guo ◽  
Man-Ryul Lee ◽  
Myung-Kwan Han ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Stem Cells ◽  
Cell Fate ◽  
Mammalian Cells ◽  
Molecular Mechanisms ◽  
Ex Vivo ◽  
Spindle Checkpoint ◽  
Cyclin B1 ◽  
Polyploid Cell ◽  
Mitotic Slippage

Abstract Ex-vivo expansion of human HSC prior to bone marrow transplantation is still an unrealized goal that could greatly extend the usefulness of this mainstay strategy for treating numerous human hematologic diseases. The safety of this process for potential use in humans depends in large part on the maintenance of karyotypic stability of HSC during expansion, a lack of which could contribute to serious, even fatal, complications such as cancer, and could also contribute to engraftment failure. The spindle checkpoint and its linkage to apoptosis initiation is one of the most important cellular processes that helps maintain chromosomal stability in rapidly proliferating cell populations by removing aneuploid and karyotypically abnormal cells via activation of cell death programs. Detailed understanding of the molecular regulation of this vital cell cycle checkpoint is important to maximize safety of in-vitro HSC expansion techniques. It is widely accepted that mammalian cells enter the next G1-phase with 4N DNA after slippage from prolonged drug-induced mitotic block caused by activation of the transient spindle checkpoint that it is from this state that polyploid/aneuploid cells initiate apoptosis. However, definitive biochemical evidence for G1 is scarce or unconvincing; in part because of methods of protein extraction required for immunoblot analysis that cannot take into account the cell cycle heterogeneity of cell cultures. We used single-cell-intracellular-flow-cytometric analysis to define important factors determining cell fate after mitotic slippage. Results from human and mouse embryonic stem cells that reenter polyploid cell cycles are compared to human somatic hematopoietic cells that die after MS. We now report for the first time that phosphorylation status of pRb, p53, CDK1, and cyclin B1 levels are important for cell fate/apoptosis decision in mitotic-slippage cells, which occurs in a unique, intervening, non-G1, tetraploid subphase. Hyperphosphorylated Rb was extremely abundant in mitotic-slippage cells, a cell signaling event usually associated with early G1-S phase transition. P53 was phosphorylated at sites known to be associated with apoptosis regulation. Cyclin A and B1 were undetectable in mitotic slippage cells; yet, CDK1 was phosphorylated at sites typically associated with its activation. Evidence is also presented raising the possibility of cyclin B1-independent CDK1 activity in mitotic-slippage cells. These findings challenge the current models of spindle checkpoint-apoptosis linkages. Our new model could have important implications for methods to maintain karyotypic stability during ex-vivo HSC expansion.

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