51
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Giannattasio S, Guaragnella N, Arbini AA, Moro L. Stress-related mitochondrial components and mitochondrial genome as targets of anticancer therapy. Chem Biol Drug Des 2013; 81:102-12. [PMID: 23253132 DOI: 10.1111/cbdd.12057] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
In addition to their role as cell powerhouse mitochondria are key organelles in the processes deciding about cell life or death that are crucial for tumor cell growth and survival, as well as for tumor cell ability to metastasize. Alterations in mitochondrial structure and functions have long been observed in cancer cells, thus targeting mitochondria as an anticancer therapeutic strategy has gained momentum recently. We will review the achievements and perspectives in the elucidation of the molecular basis for developing mitochondrial-targeted compounds as potential anticancer agents with special attention to mitochondrial DNA mutations and mitochondrial dysfunction. Molecules/agents candidate to affect mitochondrial metabolism in cancer cells will be dealt with, with a particular focus on approaches targeting defects in the mitochondrial genome.
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Affiliation(s)
- Sergio Giannattasio
- Institute of Biomembranes and Bioenergetics, National Research Council, Via Amendola 165/a, 70126 Bari, Italy.
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52
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Xu YF, Létisse F, Absalan F, Lu W, Kuznetsova E, Brown G, Caudy AA, Yakunin AF, Broach JR, Rabinowitz JD. Nucleotide degradation and ribose salvage in yeast. Mol Syst Biol 2013; 9:665. [PMID: 23670538 PMCID: PMC4039369 DOI: 10.1038/msb.2013.21] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2013] [Accepted: 04/08/2013] [Indexed: 12/30/2022] Open
Abstract
Nucleotide degradation is a universal metabolic capability. Here we combine metabolomics, genetics and biochemistry to characterize the yeast pathway. Nutrient starvation, via PKA, AMPK/SNF1, and TOR, triggers autophagic breakdown of ribosomes into nucleotides. A protein not previously associated with nucleotide degradation, Phm8, converts nucleotide monophosphates into nucleosides. Downstream steps, which involve the purine nucleoside phosphorylase, Pnp1, and pyrimidine nucleoside hydrolase, Urh1, funnel ribose into the nonoxidative pentose phosphate pathway. During carbon starvation, the ribose-derived carbon accumulates as sedoheptulose-7-phosphate, whose consumption by transaldolase is impaired due to depletion of transaldolase's other substrate, glyceraldehyde-3-phosphate. Oxidative stress increases glyceraldehyde-3-phosphate, resulting in rapid consumption of sedoheptulose-7-phosphate to make NADPH for antioxidant defense. Ablation of Phm8 or double deletion of Pnp1 and Urh1 prevent effective nucleotide salvage, resulting in metabolite depletion and impaired survival of starving yeast. Thus, ribose salvage provides means of surviving nutrient starvation and oxidative stress.
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Affiliation(s)
- Yi-Fan Xu
- Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA
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53
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Zhang F, Pracheil T, Thornton J, Liu Z. Adenosine Triphosphate (ATP) Is a Candidate Signaling Molecule in the Mitochondria-to-Nucleus Retrograde Response Pathway. Genes (Basel) 2013; 4:86-100. [PMID: 24605246 PMCID: PMC3899953 DOI: 10.3390/genes4010086] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Revised: 03/09/2013] [Accepted: 03/15/2013] [Indexed: 01/08/2023] Open
Abstract
Intracellular communication from the mitochondria to the nucleus is achieved via the retrograde response. In budding yeast, the retrograde response, also known as the RTG pathway, is regulated positively by Rtg1, Rtg2, Rtg3 and Grr1 and negatively by Mks1, Lst8 and two 14-3-3 proteins, Bmh1/2. Activation of retrograde signaling leads to activation of Rtg1/3, two basic helix-loop-helix leucine zipper transcription factors. Rtg1/3 activation requires Rtg2, a cytoplasmic protein with an N-terminal adenosine triphosphate (ATP) binding domain belonging to the actin/Hsp70/sugar kinase superfamily. The critical regulatory step of the retrograde response is the interaction between Rtg2 and Mks1. Rtg2 binds to and inactivates Mks1, allowing for activation of Rtg1/3 and the RTG pathway. When the pathway is inactive, Mks1 has dissociated from Rtg2 and bound to Bmh1/2, preventing activation of Rtg1/3. What signals association or disassociation of Mks1 and Rtg2 is unknown. Here, we show that ATP at physiological concentrations dissociates Mks1 from Rtg2 in a highly cooperative fashion. We report that ATP-mediated dissociation of Mks1 from Rtg2 is conserved in two other fungal species, K. lactis and K. waltii. Activation of Rtg1/3 upregulates expression of genes encoding enzymes catalyzing the first three reactions of the Krebs cycle, which is coupled to ATP synthesis through oxidative phosphorylation. Therefore, we propose that the retrograde response is an ATP homeostasis pathway coupling ATP production with ATP-mediated repression of the retrograde response by releasing Mks1 from Rtg2.
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Affiliation(s)
- Feng Zhang
- Department of Molecular Biology, UT Southwestern Medical Center, Dallas, TX, USA; E-Mails: (F.Z.); (J.T.)
| | - Tammy Pracheil
- Department of Biological Sciences, University of New Orleans, 2000 Lakeshore Drive, New Orleans, LA 70148, USA; E-Mail:
| | - Janet Thornton
- Department of Molecular Biology, UT Southwestern Medical Center, Dallas, TX, USA; E-Mails: (F.Z.); (J.T.)
| | - Zhengchang Liu
- Department of Biological Sciences, University of New Orleans, 2000 Lakeshore Drive, New Orleans, LA 70148, USA; E-Mail:
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +1-504-280-6314; Fax: +1-504-280-6121
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54
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Giannattasio S, Guaragnella N, Zdralević M, Marra E. Molecular mechanisms of Saccharomyces cerevisiae stress adaptation and programmed cell death in response to acetic acid. Front Microbiol 2013; 4:33. [PMID: 23430312 PMCID: PMC3576806 DOI: 10.3389/fmicb.2013.00033] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Accepted: 02/05/2013] [Indexed: 01/07/2023] Open
Abstract
Beyond its classical biotechnological applications such as food and beverage production or as a cell factory, the yeast Saccharomyces cerevisiae is a valuable model organism to study fundamental mechanisms of cell response to stressful environmental changes. Acetic acid is a physiological product of yeast fermentation and it is a well-known food preservative due to its antimicrobial action. Acetic acid has recently been shown to cause yeast cell death and aging. Here we shall focus on the molecular mechanisms of S. cerevisiae stress adaptation and programmed cell death in response to acetic acid. We shall elaborate on the intracellular signaling pathways involved in the cross-talk of pro-survival and pro-death pathways underlying the importance of understanding fundamental aspects of yeast cell homeostasis to improve the performance of a given yeast strain in biotechnological applications.
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Affiliation(s)
- Sergio Giannattasio
- Istituto di Biomembrane e Bioenergetica, Consiglio Nazionale delle Ricerche Bari, Italy
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55
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Jazwinski SM. The retrograde response: when mitochondrial quality control is not enough. BIOCHIMICA ET BIOPHYSICA ACTA 2013. [PMID: 22374136 DOI: 10.1016/j.bbamcr.2012.02.010 [epub ahead of print]] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Mitochondria are responsible for generating adenosine triphosphate (ATP) and metabolic intermediates for biosynthesis. These dual functions require the activity of the electron transport chain in the mitochondrial inner membrane. The performance of these electron carriers is imperfect, resulting in release of damaging reactive oxygen species. Thus, continued mitochondrial activity requires maintenance. There are numerous means by which this quality control is ensured. Autophagy and selective mitophagy are among them. However, the cell inevitably must compensate for declining quality control by activating a variety of adaptations that entail the signaling of the presence of mitochondrial dysfunction to the nucleus. The best known of these is the retrograde response. This signaling pathway is triggered by the loss of mitochondrial membrane potential, which engages a series of signal transduction proteins, and it culminates in the induction of a broad array of nuclear target genes. One of the hallmarks of the retrograde response is its capacity to extend the replicative life span of the cell. The retrograde signaling pathway interacts with several other signaling pathways, such as target of rapamycin (TOR) and ceramide signaling. All of these pathways respond to stress, including metabolic stress. The retrograde response is also linked to both autophagy and mitophagy at the gene and protein activation levels. Another quality control mechanism involves age-asymmetry in the segregation of dysfunctional mitochondria. One of the processes that impinge on this age-asymmetry is related to biogenesis of the organelle. Altogether, it is apparent that mitochondrial quality control constitutes a complex network of processes, whose full understanding will require a systems approach. This article is part of a Special Issue entitled: Protein Import and Quality Control in Mitochondria and Plastids.
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Affiliation(s)
- S Michal Jazwinski
- Tulane Center for Aging and Department of Medicine, Tulane University Health Sciences Center, New Orleans, LA 70112, USA.
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56
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Ruiz-Roig C, Noriega N, Duch A, Posas F, de Nadal E. The Hog1 SAPK controls the Rtg1/Rtg3 transcriptional complex activity by multiple regulatory mechanisms. Mol Biol Cell 2012; 23:4286-96. [PMID: 22956768 PMCID: PMC3484105 DOI: 10.1091/mbc.e12-04-0289] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The retrograde (RTG) pathway transcription factors Rtg1 and Rtg3 are shown to be targets of the Hog1 stress-activated protein kinase (SAPK). Hog1 acts on the RTG complex at multiple levels to mediate gene expression upon stress. The SAPK is required for the nuclear accumulation of the complex, the recruitment of the complex at RTG-responsive promoters, and the regulation of Rtg3 transcriptional activity. Cells modulate expression of nuclear genes in response to alterations in mitochondrial function, a response termed retrograde (RTG) regulation. In budding yeast, the RTG pathway relies on Rtg1 and Rtg3 basic helix-loop-helix leucine Zipper transcription factors. Exposure of yeast to external hyperosmolarity activates the Hog1 stress-activated protein kinase (SAPK), which is a key player in the regulation of gene expression upon stress. Several transcription factors, including Sko1, Hot1, the redundant Msn2 and Msn4, and Smp1, have been shown to be directly controlled by the Hog1 SAPK. The mechanisms by which Hog1 regulates their activity differ from one to another. In this paper, we show that Rtg1 and Rtg3 transcription factors are new targets of the Hog1 SAPK. In response to osmostress, RTG-dependent genes are induced in a Hog1-dependent manner, and Hog1 is required for Rtg1/3 complex nuclear accumulation. In addition, Hog1 activity regulates Rtg1/3 binding to chromatin and transcriptional activity. Therefore Hog1 modulates Rtg1/3 complex activity by multiple mechanisms in response to stress. Overall our data suggest that Hog1, through activation of the RTG pathway, contributes to ensure mitochondrial function as part of the Hog1-mediated osmoadaptive response.
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Affiliation(s)
- Clàudia Ruiz-Roig
- Cell Signaling Unit, Departament de Ciències Experimentals i de la Salut, Universitat Pompeu Fabra, E-08003 Barcelona, Spain
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57
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Liu Q, Ren T, Fresques T, Oppliger W, Niles BJ, Hur W, Sabatini DM, Hall MN, Powers T, Gray NS. Selective ATP-competitive inhibitors of TOR suppress rapamycin-insensitive function of TORC2 in Saccharomyces cerevisiae. ACS Chem Biol 2012; 7:982-7. [PMID: 22496512 DOI: 10.1021/cb300058v] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The target of rapamycin (TOR) is a critical regulator of growth, survival, and energy metabolism. The allosteric TORC1 inhibitor rapamycin has been used extensively to elucidate the TOR related signal pathway but is limited by its inability to inhibit TORC2. We used an unbiased cell proliferation assay of a kinase inhibitor library to discover QL-IX-55 as a potent inhibitor of S. cerevisiae growth. The functional target of QL-IX-55 is the ATP-binding site of TOR2 as evidenced by the discovery of resistant alleles of TOR2 through rational design and unbiased selection strategies. QL-IX-55 is capable of potently inhibiting both TOR complex 1 and 2 (TORC1 and TORC2) as demonstrated by biochemical IP kinase assays (IC(50) <50 nM) and cellular assays for inhibition of substrate YPK1 phosphorylation. In contrast to rapamycin, QL-IX-55 is capable of inhibiting TORC2-dependent transcription, which suggests that this compound will be a powerful probe to dissect the Tor2/TORC2-related signaling pathway in yeast.
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Affiliation(s)
- Qingsong Liu
- Department
of Cancer Biology, Dana-Farber Cancer Institute, 44 Binney Street, Boston,
Massachusetts 02115, United States
- Department of Biology Chemistry
and Molecular Pharmacology, Harvard Medical School, 250 Longwood Avenue, Boston, Massachusetts 02115, United States
| | - Tao Ren
- Harvard Medical School, Boston, Massachusetts 02115, United States
| | - Tara Fresques
- Department of Molecular and
Cellular Biology, College of Biological Sciences, University of California, Davis, California 95616, United States
| | | | - Brad J. Niles
- Department of Molecular and
Cellular Biology, College of Biological Sciences, University of California, Davis, California 95616, United States
| | - Wooyoung Hur
- Department
of Cancer Biology, Dana-Farber Cancer Institute, 44 Binney Street, Boston,
Massachusetts 02115, United States
- Department of Biology Chemistry
and Molecular Pharmacology, Harvard Medical School, 250 Longwood Avenue, Boston, Massachusetts 02115, United States
| | - David M. Sabatini
- Whitehead Institute for Biomedical Research, 9 Cambridge Center, Cambridge,
Massachusetts 02142, United States
- Howard Hughes Medical Institute,
Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- Koch Center for Integrative Cancer Research at MIT, 77 Massachusetts
Avenue, Cambridge, Massachusetts 02139, United States
| | | | - Ted Powers
- Department of Molecular and
Cellular Biology, College of Biological Sciences, University of California, Davis, California 95616, United States
| | - Nathanael S. Gray
- Department
of Cancer Biology, Dana-Farber Cancer Institute, 44 Binney Street, Boston,
Massachusetts 02115, United States
- Department of Biology Chemistry
and Molecular Pharmacology, Harvard Medical School, 250 Longwood Avenue, Boston, Massachusetts 02115, United States
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58
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Jazwinski SM, Kriete A. The yeast retrograde response as a model of intracellular signaling of mitochondrial dysfunction. Front Physiol 2012; 3:139. [PMID: 22629248 PMCID: PMC3354551 DOI: 10.3389/fphys.2012.00139] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 04/26/2012] [Indexed: 12/03/2022] Open
Abstract
Mitochondrial dysfunction activates intracellular signaling pathways that impact yeast longevity, and the best known of these pathways is the retrograde response. More recently, similar responses have been discerned in other systems, from invertebrates to human cells. However, the identity of the signal transducers is either unknown or apparently diverse, contrasting with the well-established signaling module of the yeast retrograde response. On the other hand, it has become equally clear that several other pathways and processes interact with the retrograde response, embedding it in a network responsive to a variety of cellular states. An examination of this network supports the notion that the master regulator NFκB aggregated a variety of mitochondria-related cellular responses at some point in evolution and has become the retrograde transcription factor. This has significant consequences for how we view some of the deficits associated with aging, such as inflammation. The support for NFκB as the retrograde response transcription factor is not only based on functional analyses. It is bolstered by the fact that NFκB can regulate Myc–Max, which is activated in human cells with dysfunctional mitochondria and impacts cellular metabolism. Myc–Max is homologous to the yeast retrograde response transcription factor Rtg1–Rtg3. Further research will be needed to disentangle the pro-aging from the anti-aging effects of NFκB. Interestingly, this is also a challenge for the complete understanding of the yeast retrograde response.
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Affiliation(s)
- S Michal Jazwinski
- Department of Medicine, Tulane Center for Aging, Tulane University Health Sciences Center New Orleans, LA, USA
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59
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The many faces of mitochondrial autophagy: making sense of contrasting observations in recent research. Int J Cell Biol 2012; 2012:431684. [PMID: 22550491 PMCID: PMC3328949 DOI: 10.1155/2012/431684] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Accepted: 12/21/2011] [Indexed: 11/17/2022] Open
Abstract
Research into the selective autophagic degradation of mitochondria—mitophagy—has intensified in recent years, yielding significant insights into the function, mechanism, and regulation of this process in the eukaryotic cell. However, while some molecular players in budding yeast, such as Atg32p, Uth1p, and Aup1p, have been identified, studies further interrogating the mechanistic and regulatory features of mitophagy have yielded inconsistent and sometimes conflicting results. In this review, we focus on the current understanding of mitophagy mechanism, induction, and regulation in yeast, and suggest that differences in experimental conditions used in the various studies of mitophagy may contribute to the observed discrepancies. Consideration and understanding of these differences may help place the mechanism and regulation of mitophagy in context, and further indicate the intricate role that this essential process plays in the life and death of eukaryotic cells.
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60
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61
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Taberner FJ, Quilis I, Sendra J, Bañó MC, Igual JC. Regulation of cell cycle transcription factor Swi5 by karyopherin Msn5. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1823:959-70. [PMID: 22374135 DOI: 10.1016/j.bbamcr.2012.02.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2011] [Revised: 01/20/2012] [Accepted: 02/13/2012] [Indexed: 01/06/2023]
Abstract
Inactivation of S. cerevisiae β-karyopherin Msn5 causes hypersensitivity to the overexpression of mitotic cyclin Clb2 and aggravates growth defects of many mutant strains in mitotic exit, suggesting a connection between Msn5 and mitotic exit. We determined that Msn5 controlled subcellular localization of the mitotic exit transcription factor Swi5, since it was required for Swi5 nuclear export. Msn5 physically interacted with the N-terminal end of Swi5. Inactivation of Msn5 caused a severe reduction in cellular levels of Swi5 protein. This effect occurred by a post-transcriptional mechanism, since SWI5 mRNA levels were not affected. The reduced amount of Swi5 in msn5 mutant cells was not due to an increased protein degradation rate, but to a defect in Swi5 synthesis. Despite the change in localization and protein level, Swi5-regulated transcription was not defective in the msn5 mutant strain. However, a high level of Swi5 was toxic in the absence of Msn5. This deleterious effect was eliminated when Swi5 nuclear import was abrogated, suggesting that nuclear export by Msn5 is important for cell physiology, because it prevents toxic Swi5 nuclear accumulation.
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62
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van Werven FJ, Amon A. Regulation of entry into gametogenesis. Philos Trans R Soc Lond B Biol Sci 2012; 366:3521-31. [PMID: 22084379 DOI: 10.1098/rstb.2011.0081] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Gametogenesis is a fundamental aspect of sexual reproduction in eukaryotes. In the unicellular fungi Saccharomyces cerevisiae (budding yeast) and Schizosaccharomyces pombe (fission yeast), where this developmental programme has been extensively studied, entry into gametogenesis requires the convergence of multiple signals on the promoter of a master regulator. Starvation signals and cellular mating-type information promote the transcription of cell fate inducers, which in turn initiate a transcriptional cascade that propels a unique type of cell division, meiosis, and gamete morphogenesis. Here, we will provide an overview of how entry into gametogenesis is initiated in budding and fission yeast and discuss potential conserved features in the germ cell development of higher eukaryotes.
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Affiliation(s)
- Folkert J van Werven
- David H. Koch Institute for Integrative Cancer Research and Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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63
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Jazwinski SM. The retrograde response: when mitochondrial quality control is not enough. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1833:400-9. [PMID: 22374136 DOI: 10.1016/j.bbamcr.2012.02.010] [Citation(s) in RCA: 102] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Revised: 02/10/2012] [Accepted: 02/12/2012] [Indexed: 12/28/2022]
Abstract
Mitochondria are responsible for generating adenosine triphosphate (ATP) and metabolic intermediates for biosynthesis. These dual functions require the activity of the electron transport chain in the mitochondrial inner membrane. The performance of these electron carriers is imperfect, resulting in release of damaging reactive oxygen species. Thus, continued mitochondrial activity requires maintenance. There are numerous means by which this quality control is ensured. Autophagy and selective mitophagy are among them. However, the cell inevitably must compensate for declining quality control by activating a variety of adaptations that entail the signaling of the presence of mitochondrial dysfunction to the nucleus. The best known of these is the retrograde response. This signaling pathway is triggered by the loss of mitochondrial membrane potential, which engages a series of signal transduction proteins, and it culminates in the induction of a broad array of nuclear target genes. One of the hallmarks of the retrograde response is its capacity to extend the replicative life span of the cell. The retrograde signaling pathway interacts with several other signaling pathways, such as target of rapamycin (TOR) and ceramide signaling. All of these pathways respond to stress, including metabolic stress. The retrograde response is also linked to both autophagy and mitophagy at the gene and protein activation levels. Another quality control mechanism involves age-asymmetry in the segregation of dysfunctional mitochondria. One of the processes that impinge on this age-asymmetry is related to biogenesis of the organelle. Altogether, it is apparent that mitochondrial quality control constitutes a complex network of processes, whose full understanding will require a systems approach. This article is part of a Special Issue entitled: Protein Import and Quality Control in Mitochondria and Plastids.
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Affiliation(s)
- S Michal Jazwinski
- Tulane Center for Aging and Department of Medicine, Tulane University Health Sciences Center, New Orleans, LA 70112, USA.
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64
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Zdralević M, Guaragnella N, Antonacci L, Marra E, Giannattasio S. Yeast as a tool to study signaling pathways in mitochondrial stress response and cytoprotection. ScientificWorldJournal 2012; 2012:912147. [PMID: 22454613 PMCID: PMC3289858 DOI: 10.1100/2012/912147] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2011] [Accepted: 11/29/2011] [Indexed: 11/17/2022] Open
Abstract
Cell homeostasis results from the balance between cell capability to adapt or succumb to environmental stress. Mitochondria, in addition to supplying cellular energy, are involved in a range of processes deciding about cellular life or death. The crucial role of mitochondria in cell death is well recognized. Mitochondrial dysfunction has been associated with the death process and the onset of numerous diseases. Yet, mitochondrial involvement in cellular adaptation to stress is still largely unexplored. Strong interest exists in pharmacological manipulation of mitochondrial metabolism and signaling. The yeast Saccharomyces cerevisiae has proven a valuable model organism in which several intracellular processes have been characterized in great detail, including the retrograde response to mitochondrial dysfunction and, more recently, programmed cell death. In this paper we review experimental evidences of mitochondrial involvement in cytoprotection and propose yeast as a model system to investigate the role of mitochondria in the cross-talk between prosurvival and prodeath pathways.
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Affiliation(s)
- Maša Zdralević
- CNR-Istituto di Biomembrane e Bioenergetica, Via Amendola 165/A, 70126 Bari, Italy
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65
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Moreau M, Azzopardi M, Clément G, Dobrenel T, Marchive C, Renne C, Martin-Magniette ML, Taconnat L, Renou JP, Robaglia C, Meyer C. Mutations in the Arabidopsis homolog of LST8/GβL, a partner of the target of Rapamycin kinase, impair plant growth, flowering, and metabolic adaptation to long days. THE PLANT CELL 2012; 24:463-81. [PMID: 22307851 PMCID: PMC3315227 DOI: 10.1105/tpc.111.091306] [Citation(s) in RCA: 170] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2011] [Revised: 01/04/2012] [Accepted: 01/15/2012] [Indexed: 05/19/2023]
Abstract
The conserved Target of Rapamycin (TOR) kinase forms high molecular mass complexes and is a major regulator of cellular adaptations to environmental cues. The Lethal with Sec Thirteen 8/G protein β subunit-like (LST8/GβL) protein is a member of the TOR complexes, and two putative LST8 genes are present in Arabidopsis thaliana, of which only one (LST8-1) is significantly expressed. The Arabidopsis LST8-1 protein is able to complement yeast lst8 mutations and interacts with the TOR kinase. Mutations in the LST8-1 gene resulted in reduced vegetative growth and apical dominance with abnormal development of flowers. Mutant plants were also highly sensitive to long days and accumulated, like TOR RNA interference lines, higher amounts of starch and amino acids, including proline and glutamine, while showing reduced concentrations of inositol and raffinose. Accordingly, transcriptomic and enzymatic analyses revealed a higher expression of genes involved in nitrate assimilation when lst8-1 mutants were shifted to long days. The transcriptome of lst8-1 mutants in long days was found to share similarities with that of a myo-inositol 1 phosphate synthase mutant that is also sensitive to the extension of the light period. It thus appears that the LST8-1 protein has an important role in regulating amino acid accumulation and the synthesis of myo-inositol and raffinose during plant adaptation to long days.
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Affiliation(s)
- Manon Moreau
- Institut Jean-Pierre Bourgin, Unité Mixte de Recherche 1318, Institut National de la Recherche Agronomique AgroParisTech, 78026 Versailles cedex, France
- Laboratoire de Génétique et Biophysique des Plantes, Unité Mixte de Recherche 7225, Commissariat à l'Energie Atomique–Institut de Biologie Environnementale et Biotechnologie–Service de Biologie Végétale et de Microbiologie Environnementales, Centre National de la Recherche Scientifique, Université Aix Marseille, Faculté des Sciences de Luminy, 13009 Marseille, France
| | - Marianne Azzopardi
- Institut Jean-Pierre Bourgin, Unité Mixte de Recherche 1318, Institut National de la Recherche Agronomique AgroParisTech, 78026 Versailles cedex, France
| | - Gilles Clément
- Institut Jean-Pierre Bourgin, Unité Mixte de Recherche 1318, Institut National de la Recherche Agronomique AgroParisTech, 78026 Versailles cedex, France
| | - Thomas Dobrenel
- Institut Jean-Pierre Bourgin, Unité Mixte de Recherche 1318, Institut National de la Recherche Agronomique AgroParisTech, 78026 Versailles cedex, France
| | - Chloé Marchive
- Institut Jean-Pierre Bourgin, Unité Mixte de Recherche 1318, Institut National de la Recherche Agronomique AgroParisTech, 78026 Versailles cedex, France
| | - Charlotte Renne
- Institut Jean-Pierre Bourgin, Unité Mixte de Recherche 1318, Institut National de la Recherche Agronomique AgroParisTech, 78026 Versailles cedex, France
| | - Marie-Laure Martin-Magniette
- Unité Mixte de Recherche 518, Institut National de la Recherche Agronomique AgroParisTech, 75005 Paris, France
- Unité de Recherche en Génomique Végétale, Unité Mixte de Recherche 1165, Institut National de la Recherche Agronomique, Université Evry Val d'Essonne, Centre National de la Recherche Scientifique, 91057 Evry cedex, France
| | - Ludivine Taconnat
- Unité de Recherche en Génomique Végétale, Unité Mixte de Recherche 1165, Institut National de la Recherche Agronomique, Université Evry Val d'Essonne, Centre National de la Recherche Scientifique, 91057 Evry cedex, France
| | - Jean-Pierre Renou
- Unité de Recherche en Génomique Végétale, Unité Mixte de Recherche 1165, Institut National de la Recherche Agronomique, Université Evry Val d'Essonne, Centre National de la Recherche Scientifique, 91057 Evry cedex, France
| | - Christophe Robaglia
- Laboratoire de Génétique et Biophysique des Plantes, Unité Mixte de Recherche 7225, Commissariat à l'Energie Atomique–Institut de Biologie Environnementale et Biotechnologie–Service de Biologie Végétale et de Microbiologie Environnementales, Centre National de la Recherche Scientifique, Université Aix Marseille, Faculté des Sciences de Luminy, 13009 Marseille, France
| | - Christian Meyer
- Institut Jean-Pierre Bourgin, Unité Mixte de Recherche 1318, Institut National de la Recherche Agronomique AgroParisTech, 78026 Versailles cedex, France
- Address correspondence to
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Miceli MV, Jiang JC, Tiwari A, Rodriguez-Quiñones JF, Jazwinski SM. Loss of mitochondrial membrane potential triggers the retrograde response extending yeast replicative lifespan. Front Genet 2012; 2:102. [PMID: 22303396 PMCID: PMC3266616 DOI: 10.3389/fgene.2011.00102] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2011] [Accepted: 12/17/2011] [Indexed: 11/20/2022] Open
Abstract
In the budding yeast Saccharomyces cerevisiae, loss of mitochondrial DNA (rho0) can induce the retrograde response under appropriate conditions, resulting in increased replicative lifespan (RLS). Although the retrograde pathway has been extensively elaborated, the nature of the mitochondrial signal triggering this response has not been clear. Mitochondrial membrane potential (MMP) was severely reduced in rho0 compared to rho+ cells, and RLS was concomitantly extended. To examine the role of MMP in the retrograde response, MMP was increased in the rho0 strain by introducing a mutation in the ATP1 gene, and it was decreased in rho+ cells by deletion of COX4. The ATP1-111 mutation in rho0 cells partially restored the MMP and reduced mean RLS to that of rho+ cells. COX4 deletion decreased MMP in rho+ cells to a value intermediate between rho+ and rho0 cells and similarly increased RLS. The increase in expression of CIT2, the diagnostic gene for the retrograde response, seen in rho0 cells, was substantially suppressed in the presence of the ATP1-111 mutation. In contrast, CIT2 expression increased in rho+ cells on deletion of COX4. Activation of the retrograde response results in the translocation of the transcription factor Rtg3 from the cytoplasm to the nucleus. Rtg3–GFP translocation to the nucleus was directly observed in rho0 and rho+cox4Δ cells, but it was blunted in rho0 cells with the ATP1-111 mutation. We conclude that a decrease in MMP is the signal that initiates the retrograde response and leads to increased RLS.
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Affiliation(s)
- Michael V Miceli
- Tulane Center for Aging and Department of Medicine, Tulane University Health Sciences Center New Orleans, LA, USA
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67
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Loewith R, Hall MN. Target of rapamycin (TOR) in nutrient signaling and growth control. Genetics 2011; 189:1177-201. [PMID: 22174183 PMCID: PMC3241408 DOI: 10.1534/genetics.111.133363] [Citation(s) in RCA: 635] [Impact Index Per Article: 48.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Accepted: 09/12/2011] [Indexed: 12/16/2022] Open
Abstract
TOR (Target Of Rapamycin) is a highly conserved protein kinase that is important in both fundamental and clinical biology. In fundamental biology, TOR is a nutrient-sensitive, central controller of cell growth and aging. In clinical biology, TOR is implicated in many diseases and is the target of the drug rapamycin used in three different therapeutic areas. The yeast Saccharomyces cerevisiae has played a prominent role in both the discovery of TOR and the elucidation of its function. Here we review the TOR signaling network in S. cerevisiae.
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Affiliation(s)
- Robbie Loewith
- Department of Molecular Biology and National Centers of Competence in Research and Frontiers in Genetics and Chemical Biology, University of Geneva, Geneva, CH-1211, Switzerland
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68
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Shmookler Reis RJ, Ayyadevara S, Crow WA, Lee T, Delongchamp RR. Gene categories differentially expressed in C. elegans age-1 mutants of extraordinary longevity: new insights from novel data-mining procedures. J Gerontol A Biol Sci Med Sci 2011; 67:366-75. [PMID: 22021389 DOI: 10.1093/gerona/glr186] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Two nonsense mutants of age-1, the Caenorhabditis elegans gene encoding phosphoinositide 3-kinase, live nearly 10-fold longer than wild-type controls and are exceptionally resistant to several stresses. Genome-wide expression analyses implicated downregulation of many more genes than were upregulated in second-generation age-1 homozygotes. Functional-annotation analysis, based on Gene Ontology terms, suggested that novel mechanisms may mediate the stronger phenotypes observed for these worms than with milder age-1 disruption. For the current study, the same microarray data were reanalyzed using novel meta-analytic procedures that we developed recently. First, gene p values were corrected for systematic biases based on the observed distribution for nonexpressed genes; these values were then combined to derive an aggregate p value for each functional-annotation term while adjusting for intergene covariance. This resulted in much better coverage of relevant gene categories, including many that were independently supported by other data. The number of nonredundant GO categories significantly distinguishing age-1 alleles of exceptional longevity increased from sevenfold to greater than ninefold, improving both sensitivity and specificity of selection for altered pathways and implicating previously unsuspected longevity mechanisms. Of 150 genes whose differential expression underlay significant GO terms in both comparisons, over half were up- or down-regulated in accord with longevity, whereas one third showed altered expression uniquely in the longest-lived age-1-null strains, consistent with the activation or suppression of pathways peculiar to strong age-1 mutants.
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69
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Alberghina L, Mavelli G, Drovandi G, Palumbo P, Pessina S, Tripodi F, Coccetti P, Vanoni M. Cell growth and cell cycle in Saccharomyces cerevisiae: basic regulatory design and protein-protein interaction network. Biotechnol Adv 2011; 30:52-72. [PMID: 21821114 DOI: 10.1016/j.biotechadv.2011.07.010] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2011] [Revised: 06/23/2011] [Accepted: 07/06/2011] [Indexed: 10/18/2022]
Abstract
In this review we summarize the major connections between cell growth and cell cycle in the model eukaryote Saccharomyces cerevisiae. In S. cerevisiae regulation of cell cycle progression is achieved predominantly during a narrow interval in the late G1 phase known as START (Pringle and Hartwell, 1981). At START a yeast cell integrates environmental and internal signals (such as nutrient availability, presence of pheromone, attainment of a critical size, status of the metabolic machinery) and decides whether to enter a new cell cycle or to undertake an alternative developmental program. Several signaling pathways, that act to connect the nutritional status to cellular actions, are briefly outlined. A Growth & Cycle interaction network has been manually curated. More than one fifth of the edges within the Growth & Cycle network connect Growth and Cycle proteins, indicating a strong interconnection between the processes of cell growth and cell cycle. The backbone of the Growth & Cycle network is composed of middle-degree nodes suggesting that it shares some properties with HOT networks. The development of multi-scale modeling and simulation analysis will help to elucidate relevant central features of growth and cycle as well as to identify their system-level properties. Confident collaborative efforts involving different expertises will allow to construct consensus, integrated models effectively linking the processes of cell growth and cell cycle, ultimately contributing to shed more light also on diseases in which an altered proliferation ability is observed, such as cancer.
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Affiliation(s)
- Lilia Alberghina
- Dipartimento di Biotecnologie e Bioscienze, Università di Milano-Bicocca, Milano, Italy.
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Belanger KD, Griffith AL, Baker HL, Hansen JN, Kovacs LAS, Seconi JS, Strine AC. The karyopherin Kap95 and the C-termini of Rfa1, Rfa2, and Rfa3 are necessary for efficient nuclear import of functional RPA complex proteins in Saccharomyces cerevisiae. DNA Cell Biol 2011; 30:641-51. [PMID: 21332387 DOI: 10.1089/dna.2010.1071] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Nuclear protein import in eukaryotic cells is mediated by karyopherin proteins, which bind to specific nuclear localization signals on substrate proteins and transport them across the nuclear envelope and into the nucleus. Replication protein A (RPA) is a nuclear protein comprised of three subunits (termed Rfa1, Rfa2, and Rfa3 in Saccharomyces cerevisiae) that binds single-stranded DNA and is essential for DNA replication, recombination, and repair. RPA associates with two different karyopherins in yeast, Kap95, and Msn5/Kap142. However, it is unclear which of these karyopherins is responsible for RPA nuclear import. We have generated GFP fusion proteins with each of the RPA subunits and demonstrate that these Rfa-GFP chimeras are functional in yeast cells. The intracellular localization of the RPA proteins in live cells is similar in wild-type and msn5Δ deletion strains but becomes primarily cytoplasmic in cells lacking functional Kap95. Truncating the C-terminus of any of the RPA subunits results in mislocalization of the proteins to the cytoplasm and a loss of protein-protein interactions between the subunits. Our data indicate that Kap95 is likely the primary karyopherin responsible for RPA nuclear import in yeast and that the C-terminal regions of Rfa1, Rfa2, and Rfa3 are essential for efficient nucleocytoplasmic transport of each RPA subunit.
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Abstract
In the past several decades the budding yeast Saccharomyces cerevisiae has emerged as a prominent model for aging research. The creation of a single-gene deletion collection covering the majority of open reading frames in the yeast genome and advances in genomic technologies have opened yeast research to genome-scale screens for a variety of phenotypes. A number of screens have been performed looking for genes that modify secondary age-associated phenotypes such as stress resistance or growth rate. More recently, moderate-throughput methods for measuring replicative life span and high-throughput methods for measuring chronological life span have allowed for the first unbiased screens aimed at directly identifying genes involved in determining yeast longevity. In this chapter we discuss large-scale life span studies performed in yeast and their implications for research related to the basic biology of aging.
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Affiliation(s)
- George L Sutphin
- Department of Pathology and the Molecular and Cellular Biology Program, University of Washington, Seattle, WA, 98195-7470, USA,
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The retrograde response retrograde response and other pathways of interorganelle communication interorganelle communication in yeast replicative aging. Subcell Biochem 2011; 57:79-100. [PMID: 22094418 DOI: 10.1007/978-94-007-2561-4_4] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
A form of mitochondria-to-nucleus signaling mitochondria-to-nucleus signaling is known to play a role in determining replicative life span in yeast. This retrograde response is triggered by experimentally-induced mitochondrial dysfunction mitochondrial dysfunction, but it also is activated during the course of normal replicative aging, allowing yeast to have as long a replicative life span as they do. The components of the retrograde signaling pathway participate in diverse cellular processes such as mitophagy, which appear to be involved in mitochondrial quality control mitochondrial quality control. This plethora of mitochondrial surveillance mitochondrial surveillance mechanisms points to the central importance of this organelle organelle in yeast replicative aging. Additional pathways pathways that monitor mitochondrial status mitochondrial status that do not apparently involve the retrograde response machinery also play a role. A unifying theme is the involvement of the target of rapamycin target of rapamycin (TOR) in both these additional pathways and in the retrograde response. The involvement of TOR brings another large family of signaling events into juxtaposition. Ceramide synthesis is regulated by TOR opening up the potential for coordination of mitochondrial status with a wide array of additional cellular processes. The retrograde response lies at the nexus of metabolic regulation metabolic regulation, stress resistance stress resistance, chromatin-dependent gene regulation chromatin-dependent gene regulation, and genome stability genome stability. In its metabolic outputs, it is related to calorie restriction,calorie restriction, which may be the result of the involvement of TOR. Retrograde response-like processes have been identified in systems other than yeast, including mammalian cells mammalian cells. The retrograde response is a prototypical pathway of interorganelle communication. Other such phenomena are emerging, such as the cross-talk cross-talk between mitochondria mitochondria and the vacuole vacuole, which involves components of the retrograde signaling pathway. The impact of these varied physiological responses on yeast replicative aging remains to be assessed.
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Domains of Tra1 important for activator recruitment and transcription coactivator functions of SAGA and NuA4 complexes. Mol Cell Biol 2010; 31:818-31. [PMID: 21149579 DOI: 10.1128/mcb.00687-10] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The Tra1 protein is a direct transcription activator target that is essential for coactivator function of both the SAGA and NuA4 histone acetyltransferase (HAT) complexes. The ∼400-kDa Saccharomyces cerevisiae Tra1 polypeptide and its human counterpart TRRAP contain 67 or 68 tandem α-helical HEAT and TPR protein repeats that extend from the N terminus to the conserved yet catalytically inactive phosphatidylinositol 3-kinase (PI3K) domain. We generated a series of mutations spanning the length of the protein and assayed for defects in transcription, coactivator recruitment, and histone acetylation at SAGA- and NuA4-dependent genes. Inviable TRA1 mutants all showed defects in SAGA and NuA4 complex stability, suggesting that similar surfaces of Tra1 mediate assembly of these two very different coactivator complexes. Nearly all of the viable Tra1 mutants showed transcription defects that fell into one of three classes: (i) defective recruitment to promoters, (ii) reduced stability of the SAGA and NuA4 HAT modules, or (iii) normal recruitment of Tra1-associated subunits but reduced HAT activity in vivo. Our results show that Tra1 recruitment at Gcn4-dependent and Rap1-dependent promoters requires the same regions of Tra1 and that separate regions of Tra1 contribute to the HAT activity and stability of the SAGA and NuA4 HAT modules.
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74
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Busti S, Coccetti P, Alberghina L, Vanoni M. Glucose signaling-mediated coordination of cell growth and cell cycle in Saccharomyces cerevisiae. SENSORS 2010; 10:6195-240. [PMID: 22219709 PMCID: PMC3247754 DOI: 10.3390/s100606195] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/07/2010] [Revised: 05/26/2010] [Accepted: 05/27/2010] [Indexed: 01/05/2023]
Abstract
Besides being the favorite carbon and energy source for the budding yeast Sacchromyces cerevisiae, glucose can act as a signaling molecule to regulate multiple aspects of yeast physiology. Yeast cells have evolved several mechanisms for monitoring the level of glucose in their habitat and respond quickly to frequent changes in the sugar availability in the environment: the cAMP/PKA pathways (with its two branches comprising Ras and the Gpr1/Gpa2 module), the Rgt2/Snf3-Rgt1 pathway and the main repression pathway involving the kinase Snf1. The cAMP/PKA pathway plays the prominent role in responding to changes in glucose availability and initiating the signaling processes that promote cell growth and division. Snf1 (the yeast homologous to mammalian AMP-activated protein kinase) is primarily required for the adaptation of yeast cell to glucose limitation and for growth on alternative carbon source, but it is also involved in the cellular response to various environmental stresses. The Rgt2/Snf3-Rgt1 pathway regulates the expression of genes required for glucose uptake. Many interconnections exist between the diverse glucose sensing systems, which enables yeast cells to fine tune cell growth, cell cycle and their coordination in response to nutritional changes.
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Affiliation(s)
- Stefano Busti
- Dipartimento di Biotecnologie e Bioscienze, Università di Milano Bicocca, Piazza della Scienza, 2-20126 Milano, Italy.
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75
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Life in the midst of scarcity: adaptations to nutrient availability in Saccharomyces cerevisiae. Curr Genet 2010; 56:1-32. [PMID: 20054690 DOI: 10.1007/s00294-009-0287-1] [Citation(s) in RCA: 163] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2009] [Revised: 12/18/2009] [Accepted: 12/19/2009] [Indexed: 12/27/2022]
Abstract
Cells of all living organisms contain complex signal transduction networks to ensure that a wide range of physiological properties are properly adapted to the environmental conditions. The fundamental concepts and individual building blocks of these signalling networks are generally well-conserved from yeast to man; yet, the central role that growth factors and hormones play in the regulation of signalling cascades in higher eukaryotes is executed by nutrients in yeast. Several nutrient-controlled pathways, which regulate cell growth and proliferation, metabolism and stress resistance, have been defined in yeast. These pathways are integrated into a signalling network, which ensures that yeast cells enter a quiescent, resting phase (G0) to survive periods of nutrient scarceness and that they rapidly resume growth and cell proliferation when nutrient conditions become favourable again. A series of well-conserved nutrient-sensory protein kinases perform key roles in this signalling network: i.e. Snf1, PKA, Tor1 and Tor2, Sch9 and Pho85-Pho80. In this review, we provide a comprehensive overview on the current understanding of the signalling processes mediated via these kinases with a particular focus on how these individual pathways converge to signalling networks that ultimately ensure the dynamic translation of extracellular nutrient signals into appropriate physiological responses.
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76
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Tucker SL, Besi MI, Galhano R, Franceschetti M, Goetz S, Lenhert S, Osbourn A, Sesma A. Common genetic pathways regulate organ-specific infection-related development in the rice blast fungus. THE PLANT CELL 2010; 22:953-72. [PMID: 20348434 PMCID: PMC2861474 DOI: 10.1105/tpc.109.066340] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2009] [Revised: 02/25/2010] [Accepted: 03/10/2010] [Indexed: 05/20/2023]
Abstract
Magnaporthe oryzae is the most important fungal pathogen of rice (Oryza sativa). Under laboratory conditions, it is able to colonize both aerial and underground plant organs using different mechanisms. Here, we characterize an infection-related development in M. oryzae produced on hydrophilic polystyrene (PHIL-PS) and on roots. We show that fungal spores develop preinvasive hyphae (pre-IH) from hyphopodia (root penetration structures) or germ tubes and that pre-IH also enter root cells. Changes in fungal cell wall structure accompanying pre-IH are seen on both artificial and root surfaces. Using characterized mutants, we show that the PMK1 (for pathogenicity mitogen-activated protein kinase 1) pathway is required for pre-IH development. Twenty mutants with altered pre-IH differentiation on PHIL-PS identified from an insertional library of 2885 M. oryzae T-DNA transformants were found to be defective in pathogenicity. The phenotypic analysis of these mutants revealed that appressorium, hyphopodium, and pre-IH formation are genetically linked fungal developmental processes. We further characterized one of these mutants, M1373, which lacked the M. oryzae ortholog of exportin-5/Msn5p (EXP5). Mutants lacking EXP5 were much less virulent on roots, suggesting an important involvement of proteins and/or RNAs transported by EXP5 during M. oryzae root infection.
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Affiliation(s)
- Sara L. Tucker
- Department of Disease and Stress Biology, John Innes Centre, Norwich NR4 7UH, United Kingdom
| | - Maria I. Besi
- Department of Disease and Stress Biology, John Innes Centre, Norwich NR4 7UH, United Kingdom
| | - Rita Galhano
- Department of Disease and Stress Biology, John Innes Centre, Norwich NR4 7UH, United Kingdom
| | - Marina Franceschetti
- Department of Disease and Stress Biology, John Innes Centre, Norwich NR4 7UH, United Kingdom
| | - Stephan Goetz
- Department of Disease and Stress Biology, John Innes Centre, Norwich NR4 7UH, United Kingdom
| | - Steven Lenhert
- Institut für Nanotechnologie, Forschungszentrum Karlsruhe, Eggenstein-Leopoldshafen 76344, Germany
| | - Anne Osbourn
- Department of Metabolic Biology, John Innes Centre, Norwich NR4 7UH, United Kingdom
| | - Ane Sesma
- Department of Disease and Stress Biology, John Innes Centre, Norwich NR4 7UH, United Kingdom
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77
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Journo D, Mor A, Abeliovich H. Aup1-mediated regulation of Rtg3 during mitophagy. J Biol Chem 2010; 284:35885-95. [PMID: 19840933 DOI: 10.1074/jbc.m109.048140] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Mitophagy is an autophagic process that degrades mitochondria by an intracellular engulfment that leads to their delivery into the lumen of the cell's hydrolytic compartment, such as the lysosome in animal cells or the vacuole in yeast. It is hypothesized that such processes serve a quality control function to prevent or slow the accumulation of malfunctioning mitochondria, which are thought in turn to underlie central aspects of the aging process in eukaryotic organisms. We recently identified a conserved mitochondrial protein phosphatase homolog, Aup1, which is required for efficient stationary phase mitophagy in yeast. In the present report, we demonstrate that the retrograde signaling pathway (RTG) is defective in aup1Delta mutants. In agreement with a role for Aup1 in the regulation of the RTG pathway, we find that deletion of RTG3, a transcription factor that mediates the RTG response, causes a defect in stationary phase mitophagy and that deletion of AUP1 leads to changes in Rtg3 phosphorylation patterns under these conditions. In addition, we find that mitophagic conditions lead to induction of RTG pathway target genes in an Aup1-dependent fashion. Thus, our results suggest that the function of Aup1 in mitophagy could be explained through its regulation of Rtg3-dependent transcription.
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Affiliation(s)
- Dikla Journo
- Department of Biochemistry and Food Science, Faculty of Agricultural, Food, and Environmental Quality Sciences, Hebrew University of Jerusalem, Rehovot 76100, Israel
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78
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Cebollero E, Reggiori F. Regulation of autophagy in yeast Saccharomyces cerevisiae. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2009; 1793:1413-21. [DOI: 10.1016/j.bbamcr.2009.01.008] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2008] [Revised: 01/04/2009] [Accepted: 01/07/2009] [Indexed: 10/21/2022]
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Singh J, Tyers M. A Rab escort protein integrates the secretion system with TOR signaling and ribosome biogenesis. Genes Dev 2009; 23:1944-58. [PMID: 19684114 DOI: 10.1101/gad.1804409] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The coupling of environmental conditions to cell growth and division is integral to cell fitness. In Saccharomyces cerevisiae, the transcription factor Sfp1 couples nutrient status to cell growth rate by controlling the expression of ribosome biogenesis (Ribi) and ribosomal protein (RP) genes. Sfp1 is localized to the nucleus in rich nutrients, but upon nutrient limitation or target of rapamycin (TOR) pathway inhibition by rapamycin, Sfp1 rapidly exits the nucleus, leading to repression of the Ribi/RP regulons. Through systematic cell-based screens we found that many components of the secretory system influence Sfp1 localization. Notably, the essential Rab escort protein Mrs6 exhibited a nutrient-sensitive interaction with Sfp1. Overexpression of Mrs6 prevented nuclear localization of Sfp1 in rich nutrients, whereas loss of Mrs6 resulted in nuclear Sfp1 localization in poor nutrients. These effects were specific to Sfp1 and independent of the protein kinase C (PKC) pathway, suggesting that Mrs6 lies in a distinct branch of TOR and ribosome biogenesis regulation. Rapamycin-resistant alleles of MRS6 were defective in the cytoplasmic retention of Sfp1, the control of cell size, and in the repression of the Ribi/RP regulons. The Sfp1-Mrs6 interaction is a nexus for growth regulation that links the secretory system and TOR-dependent nutrient signaling to ribosome biogenesis.
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Affiliation(s)
- Jaspal Singh
- Department of Molecular Genetics, University of Toronto, Ontario, Canada
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80
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Shin CS, Kim SY, Huh WK. TORC1 controls degradation of the transcription factor Stp1, a key effector of the SPS amino-acid-sensing pathway in Saccharomyces cerevisiae. J Cell Sci 2009; 122:2089-99. [PMID: 19494127 DOI: 10.1242/jcs.047191] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The target of rapamycin (TOR) signaling pathway plays crucial roles in the regulation of eukaryotic cell growth. In Saccharomyces cerevisiae, nitrogen sources in the extracellular environment activate the TOR signaling pathway. However, the precise mechanisms underlying the regulation of TOR activity in response to extracellular nitrogen sources are poorly understood. Here, we report that degradation of Stp1, a transcription factor for amino acid uptake and a key effector of the SPS amino-acid-sensing pathway, is controlled by TOR activity in S. cerevisiae. Using a genome-wide protein localization study, we found that Stp1 disappeared from the nucleus upon inactivation of TOR complex 1 (TORC1) by rapamycin, suggesting the involvement of Stp1 in the TOR signaling pathway. Supporting this notion, a knockout mutant for the STP1 gene was found to be hypersensitive to rapamycin, and overexpression of STP1 conferred resistance to rapamycin. Interestingly, we found that the rapamycin-induced disappearance of Stp1 from the nucleus resulted from Stp1 degradation, which was dependent on the activity of a protein phosphatase 2A (PP2A)-like phosphatase, Sit4, which is a well-known downstream effector of TORC1. Taken together, our findings highlight an intimate connection between the amino-acid-sensing pathway and the rapamycin-sensitive TOR signaling pathway.
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Affiliation(s)
- Chun-Shik Shin
- School of Biological Sciences and Research Center for Functional Cellulomics, Institute of Microbiology, Seoul National University, Seoul 151-747, Republic of Korea
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81
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Neklesa TK, Davis RW. A genome-wide screen for regulators of TORC1 in response to amino acid starvation reveals a conserved Npr2/3 complex. PLoS Genet 2009; 5:e1000515. [PMID: 19521502 PMCID: PMC2686269 DOI: 10.1371/journal.pgen.1000515] [Citation(s) in RCA: 118] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2008] [Accepted: 05/12/2009] [Indexed: 12/02/2022] Open
Abstract
TORC1 is a central regulator of cell growth in response to amino acid availability, yet little is known about how it is regulated. Here, we performed a reverse genetic screen in yeast for genes necessary to inactivate TORC1. The screen consisted of monitoring the expression of a TORC1 sensitive GFP-based transcriptional reporter in all yeast deletion strains using flow cytometry. We find that in response to amino acid starvation, but not to carbon starvation or rapamycin treatment, cells lacking NPR2 and NPR3 fail to fully (1) activate transcription factors Gln3/Gat1, (2) dephosphorylate TORC1 effector Npr1, and (3) repress ribosomal protein gene expression. Both mutants show proliferation defects only in media containing a low quality nitrogen source, such as proline or ammonia, whereas no defects are evident when cells are grown in the presence of glutamine or peptone mixture. Proliferation defects in npr2Δ and npr3Δ cells can be completely rescued by artificially inhibiting TORC1 by rapamycin, demonstrating that overactive TORC1 in both strains prevents their ability to adapt to an environment containing a low quality nitrogen source. A biochemical purification of each demonstrates that Npr2 and Npr3 form a heterodimer, and this interaction is evolutionarily conserved since the human homologs of NPR2 and NPR3 (NPRL2 and NPRL3, respectively) also co-immunoprecipitate. We conclude that, in yeast, the Npr2/3 complex mediates an amino acid starvation signal to TORC1. Before a eukaryotic cell commits to cell division it must be large enough so that both daughter cells would be of viable size. The control of cell size is largely mediated by nutritional input signals via an evolutionarily conserved protein complex termed TORC1. In particular, TORC1 has been shown to sense the level of amino acids and its activity correlates with the level of amino acids present in the media. Yet, it is largely unknown how TORC1 senses amino acids. Here we demonstrate that the evolutionarily conserved Npr2/3 complex mediates the amino acid scarcity signal to TORC1. Cells lacking NPR2 and NPR3 genes fail to inactivate TORC1 when amino acids are scarce. Overactive TORC1 prevents these cells from adapting to an amino acid scarce environment, and, as a result, these cells are unable to proliferate in media that is not rich in amino acids. Artificially inhibiting TORC1 with rapamycin can completely rescue these defects. These results provide insight into how cells sense amino acid deficiency. Moreover, as deletions of NPR2 have been implicated in tumor growth, these results offer a fertile ground to study the role overactive TORC1 might play in those cancers.
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Affiliation(s)
- Taavi K Neklesa
- Department of Biochemistry, Stanford University, Stanford, CA, USA.
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82
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Woo DK, Poyton RO. The absence of a mitochondrial genome in rho0 yeast cells extends lifespan independently of retrograde regulation. Exp Gerontol 2009; 44:390-7. [PMID: 19285548 DOI: 10.1016/j.exger.2009.03.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2008] [Revised: 02/26/2009] [Accepted: 03/03/2009] [Indexed: 10/21/2022]
Abstract
The absence of mtDNA in rho0 yeast cells affects both respiration and mitochondrial-nuclear communication (e.g., retrograde regulation, intergenomic signaling, or pleiotropic drug resistance). Previously, it has been reported that some rho0 strains have increased replicative lifespans, attributable to the lack of respiration and retrograde regulation. Here, we have been able to confirm that rho0 cells exhibit increased replicative lifespans but have found that this is not associated with the lack of respiration or reduced oxidative stress but instead, is related to the lack of mtDNA per se in rho0 cells. Also, we find no correlation between the strength of retrograde regulation and lifespan. Furthermore, we find that pdr3- or rtg2- mutations are not responsible for lifespan extension in rho0 cells, ruling out a specific role for PDR3-pleiotropic drug resistance or RGT2-retrograde regulation pathways in the extended lifespans of rho0 cells. Surprisingly, Rtg3p, which acts downstream of Rtg2p, is required for lifespan increase in rho0 cells. Together, these findings indicate that the loss of mtDNA per se and not the lack of respiration lead to extended longevity in rho0 cells. They also suggest that Rtg3p, acting independently of retrograde regulation, mediates this effect, possibly via intergenomic signaling.
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Affiliation(s)
- Dong Kyun Woo
- The Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309, USA
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83
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Abstract
Yeast cells sense the amount and quality of external nutrients through multiple interconnected signaling networks, which allow them to adjust their metabolism, transcriptional profile and developmental program to adapt readily and appropriately to changing nutritional states. We present our current understanding of the nutritional sensing networks yeast cells rely on for perceiving the nutritional landscape, with particular emphasis on those sensitive to carbon and nitrogen sources. We describe the means by which these networks inform the cell's decision among the different developmental programs available to them-growth, quiescence, filamentous development, or meiosis/sporulation. We conclude that the highly interconnected signaling networks provide the cell with a highly nuanced view of the environment and that the cell can interpret that information through a sophisticated calculus to achieve optimum responses to any nutritional condition.
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Affiliation(s)
- Shadia Zaman
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA
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84
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Smets B, De Snijder P, Engelen K, Joossens E, Ghillebert R, Thevissen K, Marchal K, Winderickx J. Genome-wide expression analysis reveals TORC1-dependent and -independent functions of Sch9. FEMS Yeast Res 2008; 8:1276-88. [DOI: 10.1111/j.1567-1364.2008.00432.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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85
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The yeast Tor signaling pathway is involved in G2/M transition via polo-kinase. PLoS One 2008; 3:e2223. [PMID: 18493323 PMCID: PMC2375053 DOI: 10.1371/journal.pone.0002223] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2008] [Accepted: 04/02/2008] [Indexed: 12/20/2022] Open
Abstract
The target of rapamycin (Tor) protein plays central roles in cell growth. Rapamycin inhibits cell growth and promotes cell cycle arrest at G1 (G0). However, little is known about whether Tor is involved in other stages of the cell division cycle. Here we report that the rapamycin-sensitive Tor complex 1 (TORC1) is involved in G2/M transition in S. cerevisiae. Strains carrying a temperature-sensitive allele of KOG1 (kog1-105) encoding an essential component of TORC1, as well as yeast cell treated with rapamycin show mitotic delay with prolonged G2. Overexpression of Cdc5, the yeast polo-like kinase, rescues the growth defect of kog1-105, and in turn, Cdc5 activity is attenuated in kog1-105 cells. The TORC1-Type2A phosphatase pathway mediates nucleocytoplasmic transport of Cdc5, which is prerequisite for its proper localization and function. The C-terminal polo-box domain of Cdc5 has an inhibitory role in nuclear translocation. Taken together, our results indicate a novel function of Tor in the regulation of cell cycle and proliferation.
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86
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Target of rapamycin and LST8 proteins associate with membranes from the endoplasmic reticulum in the unicellular green alga Chlamydomonas reinhardtii. EUKARYOTIC CELL 2007; 7:212-22. [PMID: 18039939 DOI: 10.1128/ec.00361-07] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The highly conserved target of rapamycin (TOR) kinase is a central controller of cell growth in all eukaryotes. TOR exists in two functionally and structurally distinct complexes, termed TOR complex 1 (TORC1) and TORC2. LST8 is a TOR-interacting protein that is present in both TORC1 and TORC2. Here we report the identification and characterization of TOR and LST8 in large protein complexes in the model photosynthetic green alga Chlamydomonas reinhardtii. We demonstrate that Chlamydomonas LST8 is part of a rapamycin-sensitive TOR complex in this green alga. Biochemical fractionation and indirect immunofluorescence microscopy studies indicate that TOR and LST8 exist in high-molecular-mass complexes that associate with microsomal membranes and are particularly abundant in the peri-basal body region in Chlamydomonas cells. A Saccharomyces cerevisiae complementation assay demonstrates that Chlamydomonas LST8 is able to functionally and structurally replace endogenous yeast LST8 and allows us to propose that binding of LST8 to TOR is essential for cell growth.
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87
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Jin R, Dobry CJ, McCown PJ, Kumar A. Large-scale analysis of yeast filamentous growth by systematic gene disruption and overexpression. Mol Biol Cell 2007; 19:284-96. [PMID: 17989363 DOI: 10.1091/mbc.e07-05-0519] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Under certain conditions of nutrient stress, the budding yeast Saccharomyces cerevisiae initiates a striking developmental transition to a filamentous form of growth, resembling developmental transitions required for virulence in closely related pathogenic fungi. In yeast, filamentous growth involves known mitogen-activated protein kinase and protein kinase A signaling modules, but the full scope of this extensive filamentous response has not been delineated. Accordingly, we have undertaken the first systematic gene disruption and overexpression analysis of yeast filamentous growth. Standard laboratory strains of yeast are nonfilamentous; thus, we constructed a unique set of reagents in the filamentous Sigma1278b strain, encompassing 3627 integrated transposon insertion alleles and 2043 overexpression constructs. Collectively, we analyzed 4528 yeast genes with these reagents and identified 487 genes conferring mutant filamentous phenotypes upon transposon insertion and/or gene overexpression. Using a fluorescent protein reporter integrated at the MUC1 locus, we further assayed each filamentous growth mutant for aberrant protein levels of the key flocculence factor Muc1p. Our results indicate a variety of genes and pathways affecting filamentous growth. In total, this filamentous growth gene set represents a wealth of yeast biology, highlighting 84 genes of uncharacterized function and an underappreciated role for the mitochondrial retrograde signaling pathway as an inhibitor of filamentous growth.
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Affiliation(s)
- Rui Jin
- Department of Molecular, Cellular, and Developmental Biology and Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109-2216, USA
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88
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Bergeron K, Julien P, Davis TA, Myre A, Thivierge MC. Long-chain n-3 fatty acids enhance neonatal insulin-regulated protein metabolism in piglets by differentially altering muscle lipid composition. J Lipid Res 2007; 48:2396-410. [PMID: 17673528 PMCID: PMC2668875 DOI: 10.1194/jlr.m700166-jlr200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
This study investigated the role of long-chain n-3 polyunsaturated fatty acids (LCn-3PUFAs) of muscle phospholipids in the regulation of neonatal metabolism. Twenty-eight piglets were weaned at 2 days of age and raised on one of two milk formulas that consisted of either a control formula supplying 0% or a formula containing 3.5% LCn-3PUFAs until 10 or 28 days of age. There was a developmental decline in the insulin sensitivity of amino acid disposal in control pigs during the first month of life, with a slope of -2.24 micromol.kg(-1).h(-1) (P = 0.01) per unit of insulin increment, as assessed using hyperinsulinemic-euglycemic-euaminoacidemic clamps. LCn-3PUFA feeding blunted this developmental decline, resulting in differing insulin sensitivities (P < 0.001). When protein metabolism was assessed under parenteral feeding-induced hyperinsulinemia, LCn-3PUFAs reduced by 16% whole body oxidative losses of amino acids (from 238 to 231 micromol.kg(-1).h(-1); P = 0.06), allowing 41% more amino acids to accrete into body proteins (from 90 to 127 micromol.kg(-1).h(-1); P = 0.06). The fractional synthetic rate of muscle mixed proteins remained unaltered by the LCn-3PUFA feeding. However, LCn-3PUFAs retarded a developmental increase in the essential-to-nonessential amino acid ratio of the muscle intracellular free pool (P = 0.05). Overall, alterations in metabolism were concomitant with a preferential incorporation of LCn-3PUFAs into muscle total membrane phospholipids (P < 0.001), in contrast to intramuscular triglycerides. These results underscore the potential role of LCn-3PUFAs as regulators of different aspects of protein metabolism in the neonate.
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Affiliation(s)
- Karen Bergeron
- Department of Animal Science, Faculty of Food Sciences and Agriculture, Laval University, Québec, Québec G1K 7P4, Canada
- Institute of Nutraceuticals and Functional Foods, Faculty of Food Sciences and Agriculture, Laval University, Québec, Québec G1K 7P4, Canada
| | - Pierre Julien
- Lipid Research Center, Laval University Hospital Center, Québec, Québec G1V 4G2, Canada
| | - Teresa A. Davis
- United States Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030
| | - Alexandre Myre
- Department of Animal Science, Faculty of Food Sciences and Agriculture, Laval University, Québec, Québec G1K 7P4, Canada
- Institute of Nutraceuticals and Functional Foods, Faculty of Food Sciences and Agriculture, Laval University, Québec, Québec G1K 7P4, Canada
| | - M. Carole Thivierge
- Department of Animal Science, Faculty of Food Sciences and Agriculture, Laval University, Québec, Québec G1K 7P4, Canada
- Institute of Nutraceuticals and Functional Foods, Faculty of Food Sciences and Agriculture, Laval University, Québec, Québec G1K 7P4, Canada
- Rowett Research Institute, Bucksburn, Aberdeen AB21 9SB, UK
- To whom correspondence should be addressed. e-mail:
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89
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Zurita-Martinez SA, Puria R, Pan X, Boeke JD, Cardenas ME. Efficient Tor signaling requires a functional class C Vps protein complex in Saccharomyces cerevisiae. Genetics 2007; 176:2139-50. [PMID: 17565946 PMCID: PMC1950620 DOI: 10.1534/genetics.107.072835] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2007] [Accepted: 05/25/2007] [Indexed: 12/26/2022] Open
Abstract
The Tor kinases regulate responses to nutrients and control cell growth. Unlike most organisms that only contain one Tor protein, Saccharomyces cerevisiae expresses two, Tor1 and Tor2, which are thought to share all of the rapamycin-sensitive functions attributable to Tor signaling. Here we conducted a genetic screen that defined the global TOR1 synthetic fitness or lethal interaction gene network. This screen identified mutations in distinctive functional categories that impaired vacuolar function, including components of the EGO/Gse and PAS complexes that reduce fitness. In addition, tor1 is lethal in combination with mutations in class C Vps complex components. We find that Tor1 does not regulate the known function of the class C Vps complex in protein sorting. Instead class C vps mutants fail to recover from rapamycin-induced growth arrest or to survive nitrogen starvation and have low levels of amino acids. Remarkably, addition of glutamate or glutamine restores viability to a tor1 pep3 mutant strain. We conclude that Tor1 is more effective than Tor2 at providing rapamycin-sensitive Tor signaling under conditions of amino acid limitation, and that an intact class C Vps complex is required to mediate intracellular amino acid homeostasis for efficient Tor signaling.
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Affiliation(s)
- Sara A Zurita-Martinez
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
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90
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Hu Z, Killion PJ, Iyer VR. Genetic reconstruction of a functional transcriptional regulatory network. Nat Genet 2007; 39:683-7. [PMID: 17417638 DOI: 10.1038/ng2012] [Citation(s) in RCA: 302] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2006] [Accepted: 03/01/2007] [Indexed: 11/09/2022]
Abstract
Although global analyses of transcription factor binding provide one view of potential transcriptional regulatory networks, regulation also occurs at levels distinct from transcription factor binding. Here, we use a genetic approach to identify targets of transcription factors in yeast and reconstruct a functional regulatory network. First, we profiled transcriptional responses in S. cerevisiae strains with individual deletions of 263 transcription factors. Then we used directed-weighted graph modeling and regulatory epistasis analysis to identify indirect regulatory relationships between these transcription factors, and from this we reconstructed a functional transcriptional regulatory network. The enrichment of promoter motifs and Gene Ontology annotations provide insight into the biological functions of the transcription factors.
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Affiliation(s)
- Zhanzhi Hu
- Center for Systems and Synthetic Biology, Institute for Cellular and Molecular Biology, Section of Molecular Genetics and Microbiology, University of Texas at Austin, 1 University Station A4800, Austin, Texas 78712, USA
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91
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Abstract
Mitochondrial retrograde signaling is a pathway of communication from mitochondria to the nucleus under normal and pathophysiological conditions. The best understood of such pathways is retrograde signaling in the budding yeast Saccharomyces cerevisiae. It involves multiple factors that sense and transmit mitochondrial signals to effect changes in nuclear gene expression; these changes lead to a reconfiguration of metabolism to accommodate cells to defects in mitochondria. Analysis of regulatory factors has provided us with a mechanistic view of regulation of retrograde signaling. Here we review advances in the yeast retrograde signaling pathway and highlight its regulatory factors and regulatory mechanisms, its physiological functions, and its connection to nutrient sensing, TOR signaling, and aging.
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Affiliation(s)
- Zhengchang Liu
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9148, USA.
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92
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Matsuo T, Otsubo Y, Urano J, Tamanoi F, Yamamoto M. Loss of the TOR kinase Tor2 mimics nitrogen starvation and activates the sexual development pathway in fission yeast. Mol Cell Biol 2007; 27:3154-64. [PMID: 17261596 PMCID: PMC1899950 DOI: 10.1128/mcb.01039-06] [Citation(s) in RCA: 155] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Fission yeast has two TOR (target of rapamycin) kinases, namely Tor1 and Tor2. Tor1 is required for survival under stressed conditions, proper G(1) arrest, and sexual development. In contrast, Tor2 is essential for growth. To analyze the functions of Tor2, we constructed two temperature-sensitive tor2 mutants. Interestingly, at the restrictive temperature, these mutants mimicked nitrogen starvation by arresting the cell cycle in G(1) phase and initiating sexual development. Microarray analysis indicated that expression of nitrogen starvation-responsive genes was induced extensively when Tor2 function was suppressed, suggesting that Tor2 normally mediates a signal from the nitrogen source. As with mammalian and budding yeast TOR, we find that fission yeast TOR also forms multiprotein complexes analogous to TORC1 and TORC2. The raptor homologue, Mip1, likely forms a complex predominantly with Tor2, producing TORC1. The rictor/Avo3 homologue, Ste20, and the Avo1 homologue, Sin1, appear to form TORC2 mainly with Tor1 but may also bind Tor2. The Lst8 homologue, Wat1, binds to both Tor1 and Tor2. Our analysis shows, with respect to promotion of G(1) arrest and sexual development, that the loss of Tor1 (TORC2) and the loss of Tor2 (TORC1) exhibit opposite effects. This highlights an intriguing functional relationship among TOR kinase complexes in the fission yeast Schizosaccharomyces pombe.
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Affiliation(s)
- Tomohiko Matsuo
- Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan.
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93
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Bahn YS, Xue C, Idnurm A, Rutherford JC, Heitman J, Cardenas ME. Sensing the environment: lessons from fungi. Nat Rev Microbiol 2007; 5:57-69. [PMID: 17170747 DOI: 10.1038/nrmicro1578] [Citation(s) in RCA: 248] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
All living organisms use numerous signal-transduction systems to sense and respond to their environments and thereby survive and proliferate in a range of biological niches. Molecular dissection of these signalling networks has increased our understanding of these communication processes and provides a platform for therapeutic intervention when these pathways malfunction in disease states, including infection. Owing to the expanding availability of sequenced genomes, a wealth of genetic and molecular tools and the conservation of signalling networks, members of the fungal kingdom serve as excellent model systems for more complex, multicellular organisms. Here, we review recent progress in our understanding of how fungal-signalling circuits operate at the molecular level to sense and respond to a plethora of environmental cues.
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Affiliation(s)
- Yong-Sun Bahn
- Department of Bioinformatics and Life Science, Soongsil University, Seoul 156-743, Korea
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94
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Teichert S, Wottawa M, Schönig B, Tudzynski B. Role of the Fusarium fujikuroi TOR kinase in nitrogen regulation and secondary metabolism. EUKARYOTIC CELL 2006; 5:1807-19. [PMID: 17031002 PMCID: PMC1595341 DOI: 10.1128/ec.00039-06] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
In Fusarium fujikuroi, the biosynthesis of gibberellins (GAs) and bikaverin is under control of AreA-mediated nitrogen metabolite repression. Thus far, the signaling components acting upstream of AreA and regulating its nuclear translocation are unknown. In Saccharomyces cerevisiae, the target of rapamycin (TOR) proteins, Tor1p and Tor2p, are key players of nutrient-mediated signal transduction to control cell growth. In filamentous fungi, probably only one TOR kinase-encoding gene exists. However, nothing is known about its function. Therefore, we investigated the role of TOR in the GA-producing fungus F. fujikuroi in order to determine whether TOR plays a role in nitrogen regulation, especially in the regulation of GA and bikaverin biosynthesis. We cloned and characterized the F. fujikuroi tor gene. However, we were not able to create knockout mutants, suggesting that TOR is essential for viability. Inhibition of TOR by rapamycin affected the expression of AreA-controlled secondary metabolite genes for GA and bikaverin biosynthesis, as well as genes involved in transcriptional and translational regulation, ribosome biogenesis, and autophagy. Deletion of fpr1 encoding the FKBP12-homologue confirmed that the effects of rapamycin are due to the specific inhibition of TOR. Interestingly, the expression of most of the TOR target genes has been previously shown to be also affected in the glutamine synthetase mutant, although in the opposite way. We demonstrate here for the first time in a filamentous fungus that the TOR kinase is involved in nitrogen regulation of secondary metabolism and that rapamycin affects also the expression of genes involved in translation control, ribosome biogenesis, carbon metabolism, and autophagy.
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Affiliation(s)
- Sabine Teichert
- Westfälische Wilhelms-Universität Münster, Institut für Botanik, Schlossgarten 3, D-48149 Münster, Germany
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95
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Kuranda K, Leberre V, Sokol S, Palamarczyk G, François J. Investigating the caffeine effects in the yeast Saccharomyces cerevisiae brings new insights into the connection between TOR, PKC and Ras/cAMP signalling pathways. Mol Microbiol 2006; 61:1147-66. [PMID: 16925551 DOI: 10.1111/j.1365-2958.2006.05300.x] [Citation(s) in RCA: 158] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Caffeine is a natural purine analogue that elicits pleiotropic effects leading ultimately to cell's death by a largely uncharacterized mechanism. Previous works have shown that this drug induces a rapid phosphorylation of the Mpk1p, the final mitogen-activated protein (MAP) kinase of the Pkc1p-mediated cell integrity pathway. In this work, we showed that this phosphorylation did not necessitate the main cell wall sensors Wsc1p and Mid2p, but was abolished upon deletion of ROM2 encoding a GDP/GTP exchange factor of Rho1p. We also showed that the caffeine-induced phosphorylation of Mpk1p was accompanied by a negligible activation of its main downstream target, the Rlm1p transcription factor. This result was consolidated by the finding that the loss of RLM1 had no consequence on the increased resistance of caffeine-treated cells to zymolyase, indicating that the cell wall modification caused by this drug is largely independent of transcriptional activation of Rlm1p-regulated genes. Additionally, the transcriptional programme elicited by caffeine resembled that of rapamycin, a potent inhibitor of the TOR1/2 kinases. Consistent with this analysis, we found that the caffeine-induced phosphorylation of Mpk1p was lost in a tor1Delta mutant. Moreover, a tor1Delta mutant was, like mutants defective in components of the Pkc1p-Mpk1p cascade, highly sensitive to caffeine. However, the hypersensitivity of a tor1 null mutant to this drug was rescued neither by sorbitol nor by adenine, which was found to outcompete caffeine effects specially on mutants in the PKC pathway. Altogether, these data indicated that Tor1 kinase is a target of caffeine, whose inhibition incidentally activates the Pkc1p-Mpk1p cascade, and that the caffeine-dependent phenotypes are largely dependent on inhibition of Tor1p-regulated cellular functions. Finally, we found that caffeine provoked, in a Rom2p-dependent manner, a transient drop in intracellular levels of cAMP, that was followed by change in expression of genes implicated in Ras/cAMP pathway. This result may pose Rom2p as a mediator in the interplay between Tor1p and the Ras/cAMP pathway.
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96
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Abstract
The story of rapamycin is a pharmaceutical fairytale. Discovered as an antifungal activity in a soil sample collected on Easter Island, this macrocyclic lactone and its derivatives are now billion dollar drugs, used in, and being evaluated for, a number of clinical applications. Taking advantage of its antifungal property, the molecular Target Of Rapamycin, TOR, was first described in the budding yeast Saccharomyces cerevisiae. TORs encode large, Ser/Thr protein kinases that reside in two distinct, structurally and functionally conserved, multi-protein complexes. In yeast, these complexes coordinate many different aspects of cell growth. TOR complex 1, TORC1, promotes protein synthesis and other anabolic processes, while inhibiting macroautophagy and other catabolic and stress-response processes. TORC2 primarily regulates cell polarity, although additional readouts of this complex are beginning to be characterized. TORC1 appears to be activated by nutrient cues and inhibited by stresses and rapamycin; however, detailed mechanisms are not known. In contrast, TORC2 is insensitive to rapamycin and physiological regulators of this complex have yet to be defined. Given the unsurpassed resources available to yeast researchers, this simple eukaryote continues to contribute to our understanding of eukaryotic cell growth in general and TOR function in particular.
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Affiliation(s)
- C De Virgilio
- Département de Microbiologie et Médecine Moléculaire, Université de Genève, CMU, Geneva, Switzerland.
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97
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Mulet JM, Martin DE, Loewith R, Hall MN. Mutual Antagonism of Target of Rapamycin and Calcineurin Signaling. J Biol Chem 2006; 281:33000-7. [PMID: 16959779 DOI: 10.1074/jbc.m604244200] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Growth and stress are generally incompatible states. Stressed cells adapt to an insult by restraining growth, and conversely, growing cells keep stress responses at bay. This is evident in many physiological settings, including for example, the effect of stress on the immune or nervous system, but the underlying signaling mechanisms mediating such mutual antagonism are poorly understood. In eukaryotes, a central activator of cell growth is the protein kinase target of rapamycin (TOR) and its namesake signaling network. Calcineurin is a conserved, Ca(2+)/calmodulin-dependent protein phosphatase and target of the immunosuppressant FK506 (tacrolimus) that is activated in yeast during stress to promote cell survival. Here we show yeast mutants defective for TOR complex 2 (TORC2) or the essential homologous TORC2 effectors, SLM1 and SLM2, exhibited constitutive activation of calcineurin-dependent transcription and actin depolarization. Conversely, cells defective in calcineurin exhibited SLM1 hyperphosphorylation and enhanced interaction between TORC2 and SLM1. Furthermore, a mutant SLM1 protein (SLM1(DeltaC14)) lacking a sequence related to the consensus calcineurin docking site (PxIxIT) was insensitive to calcineurin, and SLM1(Delta)(C14) slm2 mutant cells were hypersensitive to oxidative stress. Thus, TORC2-SLM signaling negatively regulates calcineurin, and calcineurin negatively regulates TORC2-SLM. These findings provide a molecular basis for the mutual antagonism of growth and stress.
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Affiliation(s)
- Jose M Mulet
- Biozentrum, University of Basel, Klingelbergstrasse 70, CH 4056 Basel, Switzerland
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98
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Reinke A, Chen JCY, Aronova S, Powers T. Caffeine Targets TOR Complex I and Provides Evidence for a Regulatory Link between the FRB and Kinase Domains of Tor1p. J Biol Chem 2006. [DOI: 10.1016/s0021-9258(19)84075-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
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99
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Scherens B, Feller A, Vierendeels F, Messenguy F, Dubois E. Identification of direct and indirect targets of the Gln3 and Gat1 activators by transcriptional profiling in response to nitrogen availability in the short and long term. FEMS Yeast Res 2006; 6:777-91. [PMID: 16879428 DOI: 10.1111/j.1567-1364.2006.00060.x] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Nitrogen catabolite repression (NCR) consists in the specific inhibition of transcriptional activation of genes encoding the permeases and catabolic enzymes needed to degrade poor nitrogen sources. Under nitrogen limitation or rapamycin treatment, NCR genes are activated by Gln3 or Gat1, or by both factors. To compare the sets of genes responding to rapamycin or to nitrogen limitation, we used DNA microarrays to establishing the expression profiles of a wild type strain, and of a double gln3Delta-gat1Delta strain, grown on glutamine, after addition of rapamycin, on proline, or after a shift from glutamine to proline. Analysis of microarray data revealed 392 genes whose expression was dependent on the nitrogen source quality. 91 genes were activated in a GATA factor-dependent manner in all growth conditions, suggesting a direct role of Gln3 and Gat1 in their expression. Other genes were only transiently up-regulated (stress-responsive genes) or down-regulated (genes encoding ribosomal proteins and translational factors) upon nitrogen limitation, and this regulation was delayed in a gln3Delta-gat1Delta strain. Repression of amino acid and nucleotide biosynthetic genes after a nitrogen shift did not depend on Gcn4. Several transporter genes were repressed as a consequence of enhanced levels of NCR-responsive permeases present at the plasma membrane.
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Affiliation(s)
- Bart Scherens
- Institut de Recherches Microbiologiques J-M Wiame, and Laboratoire de Microbiologie, Université Libre de Bruxelles, Brussels, Belgium
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100
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Reinke A, Chen JCY, Aronova S, Powers T. Caffeine targets TOR complex I and provides evidence for a regulatory link between the FRB and kinase domains of Tor1p. J Biol Chem 2006; 281:31616-26. [PMID: 16923813 DOI: 10.1074/jbc.m603107200] [Citation(s) in RCA: 143] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The target of rapamycin (TOR) kinase is an important regulator of growth in eukaryotic cells. In budding yeast, Tor1p and Tor2p function as part of two distinct protein complexes, TORC1 and TORC2, where TORC1 is specifically inhibited by the antibiotic rapamycin. Significant insight into TORC1 function has been obtained using rapamycin as a specific small molecule inhibitor of TOR activity. Here we show that caffeine acts as a distinct and novel small molecule inhibitor of TORC1: (i) deleting components specific to TORC1 but not TORC2 renders cells hypersensitive to caffeine; (ii) rapamycin and caffeine display remarkably similar effects on global gene expression; and (iii) mutations were isolated in Tor1p, a component specific to TORC1, that confers significant caffeine resistance both in vivo and in vitro. Strongest resistance requires two simultaneous mutations in TOR1, the first at either one of two highly conserved positions within the FRB (rapamycin binding) domain and a second at a highly conserved position within the ATP binding pocket of the kinase domain. Biochemical and genetic analyses of these mutant forms of Tor1p support a model wherein functional interactions between the FRB and kinase domains, as well as between the FRB domain and the TORC1 component Kog1p, regulate TOR activity as well as contribute to the mechanism of caffeine resistance.
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Affiliation(s)
- Aaron Reinke
- Section of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, California 95616, USA
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