Controlling cell growth and survival through regulated nutrient transporter expression

2007 ◽  
Vol 406 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Aimee L. Edinger
Keyword(s):  
Cell Growth ◽  
Mammalian Cells ◽  
Growth Control ◽  
Cellular Growth ◽  
Growth And Survival ◽  
Tumour Suppression ◽  
Nutrient Transporter ◽  
Phosphoinositide 3 Kinase ◽  
Cell Growth And Proliferation ◽  
Transporter Expression

Although all cells depend upon nutrients they acquire from the extracellular space, surprisingly little is known about how nutrient uptake is regulated in mammalian cells. Most nutrients are brought into cells by means of specific transporter proteins. In yeast, the expression and trafficking of a wide variety of nutrient transporters is controlled by the TOR (target of rapamycin) kinase. Consistent with this, recent studies in mammalian cells have shown that mTOR (mammalian TOR) and the related protein, PI3K (phosphoinositide 3-kinase), play central roles in coupling nutrient transporter expression to the availability of extrinsic trophic and survival signals. In the case of lymphocytes, it has been particularly well established that these extrinsic signals stimulate cell growth and proliferation in part by regulating nutrient transporter expression. The ability of growth factors to control nutrient access may also play an important role in tumour suppression: the non-homoeostatic growth of tumour cells requires that nutrient transporter expression is uncoupled from trophic factor availability. Also supporting a link between nutrient transporter expression levels and oncogenesis, several recent studies demonstrate that nutrient transporter expression drives, rather than simply parallels, cellular metabolism. This review summarizes the evidence that regulated nutrient transporter expression plays a central role in cellular growth control and highlights the implications of these findings for human disease.

scholarly journals TGFβ/Activin signalling is required for ribosome biogenesis and cell growth in Drosophila salivary glands

Open Biology ◽  
2017 ◽  
Vol 7 (1) ◽  
pp. 160258 ◽  
Author(s):  
Torcato Martins ◽  
Nadia Eusebio ◽  
Andreia Correia ◽  
Joana Marinho ◽  
Fernando Casares ◽  
...  
Keyword(s):  
Cell Growth ◽  
Salivary Glands ◽  
Ribosomal Proteins ◽  
Ribosome Biogenesis ◽  
Growth Control ◽  
Tissue Growth ◽  
Cellular Growth ◽  
Nucleolar Structure ◽  
Cell Growth And Proliferation ◽  
Tgfβ Superfamily

Signalling by TGFβ superfamily factors plays an important role in tissue growth and cell proliferation. In Drosophila , the activity of the TGFβ/Activin signalling branch has been linked to the regulation of cell growth and proliferation, but the cellular and molecular basis for these functions are not fully understood. In this study, we show that both the RII receptor Punt (Put) and the R-Smad Smad2 are strongly required for cell and tissue growth. Knocking down the expression of Put or Smad2 in salivary glands causes alterations in nucleolar structure and functions. Cells with decreased TGFβ/Activin signalling accumulate intermediate pre-rRNA transcripts containing internal transcribed spacer 1 regions accompanied by the nucleolar retention of ribosomal proteins. Thus, our results show that TGFβ/Activin signalling is required for ribosomal biogenesis, a key aspect of cellular growth control. Importantly, overexpression of Put enhanced cell growth induced by Drosophila Myc, a well-characterized inducer of nucleolar hypertrophy and ribosome biogenesis.

scholarly journals HDAC8 Mediates Homologous Recombination and Cytoskeleton Integrity in Myeloma with Potential Impact on Cell Growth and Survival

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 416-416
Author(s):  
Maria Gkotzamanidou ◽  
Masood Shammas ◽  
Jesus Martin Sanchez ◽  
Lai Ding ◽  
Stephane Minvielle ◽  
...  
Keyword(s):  
Dna Damage ◽  
Cell Growth ◽  
Homologous Recombination ◽  
Cellular Growth ◽  
Luciferase Reporter ◽  
Dna Integrity ◽  
Newly Diagnosed ◽  
Inhibition Of Proliferation ◽  
Growth And Survival

Abstract Epigenomic changes have become an important component of cellular regulation and ultimately, of our understanding of oncogenomics in Multiple Myeloma (MM) as well as in other cancers. In recent years, both clinical and preclinical studies have confirmed that MM is vulnerable to epigenetic intervention, with histone deacetylases (HDACs) emerging as the most promising epigenetic targets. Although Pan-HDAC inhibitors are effective as therapeutic agents, there is increasing emphasis on understanding the biological and molecular roles of individual HDACs. Here we have evaluated the role of HDAC8, a member of Class I HDAC isoenzymes in MM. First, we evaluated the expression of HDAC8 in 172 newly-diagnosed MM patients from the IFM myeloma dataset and observed HDAC8 overexpression as well as its significant correlation with poor survival outcome (p<0.0015). We further evaluated the expression of HDAC8 in HMCLs (probe ID_223909-s_at, 223345_at) and confirmed the high expression and its cytoplasmic and nuclear localization in all six MM cells lines studied (MM1S, OPM2, RPMI8226, U266, MOLP8 and NCI-H929) and in primary bone marrow plasma cells (CD138+) from newly diagnosed MM patients (N=3). To address the functional role of HDAC8 in MM biology and to evaluate its potency as therapeutic target, we used a lentiviral-shRNA delivery system for HDAC8-knockdown in MM1S and OPM2 myeloma cells. The HDAC8 depletion in HMCLs resulted in significant inhibition of proliferation of MM at 1 week as measured by 3[H]-thymidine assay, and as decrease in colony formation evaluated after 3 weeks post transfection (p<.001). We observed similar cell growth inhibition using PCI-34051, a small molecule HDAC8 inhibitor. Interestingly, the combination of HDAC8 inhibitor with melphalan or bendamustine enhanced the anti-MM effects of the DNA damaging agents (all p<0.01) and was confirmed to be synergistic using Calcusyn software. Immunoblotting using a panel of 15 antibodies for DNA damage response (DDR) pathway proteins (including γH2Ax, pATM, pATR, pBRCA1, pBRCA2, pCHK2, pCHK1, ku70, RPA70, 53BP1, DNA-PKs, pP53) confirmed increased levels of DNA damage in OPM2 and MM1S cells with HDAC8 depletion. In consistence with this observation HDAC8 knockdown led to decreased homologous recombination (HR) activity as measured by a transient direct repeat DsRED-GFP/I-SceI plasmid-based assay. We performed singe cell electrophoresis under neutral conditions (comet-assay) in OPM2 and MM1S after HDAC8 depletion with or without exposure to gamma irradiation (γ-IR), and in OPM2 and MM1S cells treated and untreated with HDAC8 inhibitor in combination with γ-IR and observed decreased repair of DSBs after γ-IR measured following HDAC8 knockdown as well as following treatment of the cells with HDAC8 inhibitor. Importantly, using laser micro-irradiation in myeloma and U2OS cells, we observed HDAC8 recruitment to DSBs sites. Moreover, the HDAC8 protein was co-localized and co-immunoprecipitated with Rad51 after IR, and with Scm3, member of cohesion complex after mitotic sychronization, suggesting its relation with cytoskeleton. We confirmed the significant alteration in expression of cohesion complex members SMC1 and RAD21 after HDAC8 depletion and re-overexpression in MM cells. In MM1s cells containing a stably integrated Rad51-luciferase reporter construct, the addition of HDAC8 inhibitor resulted in a decrease in Rad51 promoter activity, confirming the immunoblotting findings. An ongoing mass spectromentry-based analysis is expected to identify thoroughly the HDAC8-interacting proteins. In conclusion, our results demonstrate an impact of aberrant epigenome on DNA integrity through connection between HDAC8 and DDR pathway, and provide insights into the effect of HDAC8 on cellular growth and survival with potent therapeutic implications in MM. Disclosures Anderson: Celgene: Consultancy; Sanofi-Aventis: Consultancy; Onyx: Consultancy; Acetylon: Scientific Founder, Scientific Founder Other; Oncoprep: Scientific Founder Other; Gilead Sciences: Consultancy.

scholarly journals A novel phosphatidylinositol(3,4,5)P3 pathway in fission yeast

2004 ◽  
Vol 166 (2) ◽  
pp. 205-211 ◽  
Author(s):  
Prasenjit Mitra ◽  
Yingjie Zhang ◽  
Lucia E. Rameh ◽  
Maria P. Ivshina ◽  
Dannel McCollum ◽  
...  
Keyword(s):  
Fission Yeast ◽  
Mammalian Cells ◽  
Class I ◽  
Unexpected Finding ◽  
Class Iii ◽  
Growth And Survival ◽  
Higher Eukaryotes ◽  
Phosphoinositide 3 Kinase ◽  
Phosphatidylinositol 4 ◽  
Phosphatase And Tensin Homologue

The mammalian tumor suppressor, phosphatase and tensin homologue deleted on chromosome 10 (PTEN), inhibits cell growth and survival by dephosphorylating phosphatidylinositol-(3,4,5)-trisphosphate (PI[3,4,5]P3). We have found a homologue of PTEN in the fission yeast, Schizosaccharomyces pombe (ptn1). This was an unexpected finding because yeast (S. pombe and Saccharomyces cerevisiae) lack the class I phosphoinositide 3-kinases that generate PI(3,4,5)P3 in higher eukaryotes. Indeed, PI(3,4,5)P3 has not been detected in yeast. Surprisingly, upon deletion of ptn1 in S. pombe, PI(3,4,5)P3 became detectable at levels comparable to those in mammalian cells, indicating that a pathway exists for synthesis of this lipid and that the S. pombe ptn1, like mammalian PTEN, suppresses PI(3,4,5)P3 levels. By examining various mutants, we show that synthesis of PI(3,4,5)P3 in S. pombe requires the class III phosphoinositide 3-kinase, vps34p, and the phosphatidylinositol-4-phosphate 5-kinase, its3p, but does not require the phosphatidylinositol-3-phosphate 5-kinase, fab1p. These studies suggest that a pathway for PI(3,4,5)P3 synthesis downstream of a class III phosphoinositide 3-kinase evolved before the appearance of class I phosphoinositide 3-kinases.

scholarly journals Exploiting cancer vulnerabilities: mTOR, autophagy, and homeostatic imbalance

2017 ◽  
Vol 61 (6) ◽  
pp. 699-710 ◽  
Author(s):  
Charlotte E. Johnson ◽  
Andrew R. Tee
Keyword(s):  
Cell Growth ◽  
Cancer Cells ◽  
Energy Homeostasis ◽  
Cellular Stress ◽  
Growth Control ◽  
Potential Therapeutic Target ◽  
Wide Range ◽  
Cell Growth And Proliferation ◽  
Mtor Complex 1 ◽  
Cell Growth Control

Mechanistic target of rapamycin (mTOR) complex 1 (mTORC1) at lysosomes plays a pivotal role in cell growth control where an array of large multiprotein complexes relay nutrient, energy, and growth signal inputs through mTORC1. In cancer cells, such regulation often becomes disconnected, leading to uncontrolled cell growth and an elevation in cellular stress. Consequently, cancer cells often lose homeostatic balance as they grow in unfavorable conditions, i.e. when nutrients and energy are limited yet mTORC1 is still aberrantly activated. Cancer cells lose signaling flexibility because of hyperactive mTORC1 that leads to heightened cellular stress and loss of nutrient and energy homeostasis, all of which are potential avenues for cancer therapy. Cancer cells often enhance mTORC1 to drive cell growth and proliferation, while also maintaining their survival. Autophagy regulation by mTORC1 is critically involved in nutrient and energy homeostasis, cell growth control, and survival. Studying mTORC1 and autophagy as a potential therapeutic target for cancer treatment has been the focus of a wide range of research over the past few decades. This review will explore the signaling pathways central to mTORC1 and autophagy regulation, and cancer vulnerabilities while considering anticancer therapies.

Growth factors regulate cell survival by controlling nutrient transporter expression

2005 ◽  
Vol 33 (1) ◽  
pp. 225-227 ◽  
Author(s):  
A.L. Edinger
Keyword(s):  
Growth Factors ◽  
Growth Factor ◽  
Cell Survival ◽  
Mammalian Cells ◽  
Mammalian Target Of Rapamycin ◽  
Chemotherapeutic Agents ◽  
Tumour Suppressor ◽  
Nutrient Transporters ◽  
Nutrient Transporter ◽  
Transporter Expression

Growth factors provide permission signals that allow mammalian cells to grow, proliferate and survive. One mechanism by which growth factors maintain this control is through the regulation of cell surface nutrient transporter expression. Following growth factor withdrawal, nutrient transporters are endocytosed and degraded in the lysosome, effectively terminating the cell's ability to obtain nutrients. This results in a state of pseudostarvation in which cells atrophy and initiate a catabolic metabolic programme in the midst of abundant extracellular nutrients. Oncogenic forms of Akt can support growth factor-independent nutrient transporter expression through a mechanism that depends upon mTOR (mammalian target of rapamycin). The ability of activated Akt to support nutrient transporter expression is an essential component of its prosurvival function. When the destruction of nutrient transporters is inhibited, cells are capable of long-term growth-factor-independent cell survival in the absence of receptor-dependent signal transduction. These results imply that proteins involved in nutrient transporter turnover in response to growth factor withdrawal are components of a novel tumour suppressor pathway. Preliminary data suggest that Rab7, a GTPase required for transporter degradation, functions as a tumour suppressor protein, as inhibiting Rab7 activity promotes colony formation in soft agar. These studies indicate that drugs affecting this pathway might have utility as anti-cancer chemotherapeutic agents.

Starvation in the midst of plenty: making sense of ceramide-induced autophagy by analysing nutrient transporter expression

2009 ◽  
Vol 37 (1) ◽  
pp. 253-258 ◽  
Author(s):  
Aimee L. Edinger
Keyword(s):  
Heat Stress ◽  
Mammalian Cells ◽  
Cellular Response ◽  
Lethal Dose ◽  
Culture Conditions ◽  
Making Sense ◽  
Nutrient Transporter ◽  
Increased Sensitivity ◽  
Methyl Pyruvate ◽  
Transporter Expression

Ceramide induces differentiation, proliferative arrest, senescence and death in mammalian cells. The mechanism by which ceramide produces these outcomes has proved difficult to define. Building on observations that ceramide stimulates autophagy, we have identified a novel mechanism of action for this sphingolipid: ceramide starves cells to death subsequent to profound nutrient transporter down-regulation. In yeast, ceramide generated in response to heat stress adaptively slows cell growth by down-regulating nutrient permeases. In mammalian cells, a lethal dose of ceramide triggers a bioenergetic crisis by so severely limiting cellular access to extracellular nutrients that autophagy is insufficient to meet the metabolic demands of the cell. In keeping with this bioenergetic explanation for ceramide toxicity, methyl pyruvate, a membrane-permeable nutrient, protects cells from ceramide-induced starvation. Also consistent with this model, we have found that the metabolic state of the cell determines its sensitivity to ceramide. Thus the increased sensitivity of cancer cells to ceramide may relate to their inflexible biosynthetic metabolic programme. These studies highlight the value of assessing nutrient transporter expression in autophagic cells and the important role that culture conditions play in determining the cellular response to ceramide.

scholarly journals Von Hippel–Lindau tumor suppressor (VHL) stimulates TOR signaling by interacting with phosphoinositide 3-kinase (PI3K)

2020 ◽  
Vol 295 (8) ◽  
pp. 2336-2347 ◽  
Author(s):  
Sun-Hong Hwang ◽  
Sunhoe Bang ◽  
Wonho Kim ◽  
Jongkyeong Chung
Keyword(s):  
Cell Growth ◽  
Mammalian Cells ◽  
Fat Body ◽  
Loss Of Function ◽  
Tor Signaling ◽  
Von Hippel Lindau ◽  
Ribosomal Protein S6 ◽  
Evolutionarily Conserved ◽  
Regulate Cell Growth ◽  
Phosphoinositide 3 Kinase

Cell growth is positively controlled by the phosphoinositide 3-kinase (PI3K)–target of rapamycin (TOR) signaling pathway under conditions of abundant growth factors and nutrients. To discover additional mechanisms that regulate cell growth, here we performed RNAi-based mosaic analyses in the Drosophila fat body, the primary metabolic organ in the fly. Unexpectedly, the knockdown of the Drosophila von Hippel–Lindau (VHL) gene markedly decreased cell size and body size. These cell growth phenotypes induced by VHL loss of function were recovered by activation of TOR signaling in Drosophila. Consistent with the genetic interactions between VHL and the signaling components of PI3K–TOR pathway in Drosophila, we observed that VHL loss of function in mammalian cells causes decreased phosphorylation of ribosomal protein S6 kinase and Akt, which represent the main activities of this pathway. We further demonstrate that VHL activates TOR signaling by directly interacting with the p110 catalytic subunit of PI3K. On the basis of the evolutionarily conserved regulation of PI3K–TOR signaling by VHL observed here, we propose that VHL plays an important role in the regulation and maintenance of proper cell growth in metazoans.

scholarly journals An improved platform for functional assessment of large protein libraries in mammalian cells

2019 ◽  
Author(s):  
Kenneth A Matreyek ◽  
Jason J Stephany ◽  
Melissa A Chiasson ◽  
Nicholas Hasle ◽  
Douglas M Fowler
Keyword(s):  
Cell Growth ◽  
Cell Lines ◽  
Mammalian Cells ◽  
Cell Function ◽  
Lentiviral Vector ◽  
Growth And Survival ◽  
Mammalian Cell Lines ◽  
Recombinant Cells ◽  
Reducing Costs ◽  
Protein Libraries

Abstract Multiplex genetic assays can simultaneously test thousands of genetic variants for a property of interest. However, limitations of existing multiplex assay methods in cultured mammalian cells hinder the breadth, speed and scale of these experiments. Here, we describe a series of improvements that greatly enhance the capabilities of a Bxb1 recombinase-based landing pad system for conducting different types of multiplex genetic assays in various mammalian cell lines. We incorporate the landing pad into a lentiviral vector, easing the process of generating new landing pad cell lines. We also develop several new landing pad versions, including one where the Bxb1 recombinase is expressed from the landing pad itself, improving recombination efficiency more than 2-fold and permitting rapid prototyping of transgenic constructs. Other versions incorporate positive and negative selection markers that enable drug-based enrichment of recombinant cells, enabling the use of larger libraries and reducing costs. A version with dual convergent promoters allows enrichment of recombinant cells independent of transgene expression, permitting the assessment of libraries of transgenes that perturb cell growth and survival. Lastly, we demonstrate these improvements by assessing the effects of a combinatorial library of oncogenes and tumor suppressors on cell growth. Collectively, these advancements make multiplex genetic assays in diverse cultured cell lines easier, cheaper and more effective, facilitating future studies probing how proteins impact cell function, using transgenic variant libraries tested individually or in combination.

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