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Hildebrandt ER, Hussain SA, Sieburg MA, Ravishankar R, Asad N, Gore S, Ito T, Hougland JL, Dore TM, Schmidt WK. Targeted genetic and small molecule disruption of N-Ras CaaX cleavage alters its localization and oncogenic potential. Bioorg Chem 2024; 147:107316. [PMID: 38583246 PMCID: PMC11098683 DOI: 10.1016/j.bioorg.2024.107316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 02/16/2024] [Accepted: 03/26/2024] [Indexed: 04/09/2024]
Abstract
Ras GTPases and other CaaX proteins undergo multiple post-translational modifications at their carboxyl-terminus. These events initiate with prenylation of a cysteine and are followed by endoproteolytic removal of the 'aaX' tripeptide and carboxylmethylation. Some CaaX proteins are only subject to prenylation, however, due to the presence of an uncleavable sequence. In this study, uncleavable sequences were used to stage Ras isoforms in a farnesylated and uncleaved state to address the impact of CaaX proteolysis on protein localization and function. This targeted strategy is more specific than those that chemically inhibit the Rce1 CaaX protease or delete the RCE1 gene because global abrogation of CaaX proteolysis impacts the entire CaaX protein proteome and effects cannot be attributed to any specific CaaX protein of the many concurrently affected. With this targeted strategy, clear mislocalization and reduced activity of farnesylated and uncleaved Ras isoforms was observed. In addition, new peptidomimetics based on cleavable Ras CaaX sequences and the uncleavable CAHQ sequence were synthesized and tested as Rce1 inhibitors using in vitro and cell-based assays. Consistently, these non-hydrolyzable peptidomimetic Rce1 inhibitors recapitulate Ras mislocalization effects when modeled on cleavable but not uncleavable CaaX sequences. These findings indicate that a prenylated and uncleavable CaaX sequence, which can be easily applied to a wide range of mammalian CaaX proteins, can be used to probe the specific impact of CaaX proteolysis on CaaX protein properties under conditions of an otherwise normally processed CaaX protein proteome.
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Affiliation(s)
- Emily R Hildebrandt
- Department of Biochemistry & Molecular Biology, University of Georgia, Athens, GA, USA
| | - Shaneela A Hussain
- New York University Abu Dhabi, Saadiyat Island, PO Box 129188, Abu Dhabi, UAE
| | | | - Rajani Ravishankar
- Department of Biochemistry & Molecular Biology, University of Georgia, Athens, GA, USA
| | - Nadeem Asad
- New York University Abu Dhabi, Saadiyat Island, PO Box 129188, Abu Dhabi, UAE
| | - Sangram Gore
- New York University Abu Dhabi, Saadiyat Island, PO Box 129188, Abu Dhabi, UAE
| | - Takahiro Ito
- Department of Biochemistry & Molecular Biology, University of Georgia, Athens, GA, USA
| | - James L Hougland
- Department of Chemistry, Syracuse University, Syracuse, NY, USA; Department of Biology, Syracuse University, Syracuse, NY, USA; BioInspired Syracuse, Syracuse University, Syracuse, NY, USA
| | - Timothy M Dore
- New York University Abu Dhabi, Saadiyat Island, PO Box 129188, Abu Dhabi, UAE; Department of Chemistry, University of Georgia, Athens, GA, USA
| | - Walter K Schmidt
- Department of Biochemistry & Molecular Biology, University of Georgia, Athens, GA, USA.
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Muth LT, Van Bogaert INA. Let it stick: Strategies and applications for intracellular plasma membrane targeting of proteins in Saccharomyces cerevisiae. Yeast 2024; 41:315-329. [PMID: 38444057 DOI: 10.1002/yea.3933] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Revised: 02/09/2024] [Accepted: 02/12/2024] [Indexed: 03/07/2024] Open
Abstract
Lipid binding domains and protein lipidations are essential features to recruit proteins to intracellular membranes, enabling them to function at specific sites within the cell. Membrane association can also be exploited to answer fundamental and applied research questions, from obtaining insights into the understanding of lipid metabolism to employing them for metabolic engineering to redirect fluxes. This review presents a broad catalog of membrane binding strategies focusing on the plasma membrane of Saccharomyces cerevisiae. Both lipid binding domains (pleckstrin homology, discoidin-type C2, kinase associated-1, basic-rich and bacterial phosphoinositide-binding domains) and co- and post-translational lipidations (prenylation, myristoylation and palmitoylation) are introduced as tools to target the plasma membrane. To provide a toolset of membrane targeting modules, respective candidates that facilitate plasma membrane targeting are showcased including their in vitro and in vivo properties. The relevance and versatility of plasma membrane targeting modules are further highlighted by presenting a selected set of use cases.
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Affiliation(s)
- Liv Teresa Muth
- Department of Biotechnology, Centre for Synthetic Biology, Ghent University, Ghent, Belgium
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Ravishankar R, Hildebrandt ER, Greenway G, Asad N, Gore S, Dore TM, Schmidt WK. Specific Disruption of Ras2 CAAX Proteolysis Alters Its Localization and Function. Microbiol Spectr 2023; 11:e0269222. [PMID: 36602340 PMCID: PMC9927470 DOI: 10.1128/spectrum.02692-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Many CAAX proteins, such as Ras GTPase, undergo a series of posttranslational modifications at their carboxyl terminus (i.e., cysteine prenylation, endoproteolysis of AAX, and carboxylmethylation). Some CAAX proteins, however, undergo prenylation-only modification, such as Saccharomyces cerevisiae Hsp40 Ydj1. We previously observed that altering the CAAX motif of Ydj1 from prenylation-only to canonical resulted in altered Ydj1 function and localization. Here, we investigated the effects of a reciprocal change that altered the well-characterized canonical CAAX motif of S. cerevisiae Ras2 to prenylation-only. We observed that the type of CAAX motif impacted Ras2 protein levels, localization, and function. Moreover, we observed that using a prenylation-only sequence to stage hyperactive Ras2-G19V as a farnesylated and nonproteolyzed intermediate resulted in a different phenotype relative to staging by a genetic RCE1 deletion strategy that simultaneously affected many CAAX proteins. These findings suggested that a prenylation-only CAAX motif is useful for probing the specific impact of CAAX proteolysis on Ras2 under conditions where other CAAX proteins are normally modified. We propose that our strategy could be easily applied to a wide range of CAAX proteins for examining the specific impact of CAAX proteolysis on their functions. IMPORTANCE CAAX proteins are subject to multiple posttranslational modifications: cysteine prenylation, CAAX proteolysis, and carboxylmethylation. For investigations of CAAX proteolysis, this study took the novel approach of using a proteolysis-resistant CAAX sequence to stage Saccharomyces cerevisiae Ras2 GTPase in a farnesylated and nonproteolyzed state. Our approach specifically limited the effects of disrupting CAAX proteolysis to Ras2. This represented an improvement over previous methods where CAAX proteolysis was inhibited by gene knockout, small interfering RNA knockdown, or biochemical inhibition of the Rce1 CAAX protease, which can lead to pleiotropic and unclear attribution of effects due to the action of Rce1 on multiple CAAX proteins. Our approach yielded results that demonstrated specific impacts of CAAX proteolysis on the function, localization, and other properties of Ras2, highlighting the utility of this approach for investigating the impact of CAAX proteolysis in other protein contexts.
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Affiliation(s)
- Rajani Ravishankar
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Emily R. Hildebrandt
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Grace Greenway
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Nadeem Asad
- New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - Sangram Gore
- New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - Timothy M. Dore
- New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
- Department of Chemistry, University of Georgia, Athens, Georgia, USA
| | - Walter K. Schmidt
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
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Bonomelli B, Busti S, Martegani E, Colombo S. Active Ras2 in mitochondria promotes regulated cell death in a cAMP/PKA pathway-dependent manner in budding yeast. FEBS Lett 2023; 597:298-308. [PMID: 36527174 DOI: 10.1002/1873-3468.14567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Revised: 11/29/2022] [Accepted: 12/01/2022] [Indexed: 12/23/2022]
Abstract
Previously, we showed that an aberrant accumulation of activated Ras in mitochondria correlates with an increase in apoptosis. In this article, we show that lack of trehalose-6P-synthase, known to trigger apoptosis in Saccharomyces cerevisiae, induces localization of active Ras proteins in mitochondria, confirming the above-mentioned correlation. Next, by characterizing the ras1Δ and ras2Δ mutants, we show that active Ras2 proteins, which accumulate in the mitochondria following addition of acetic acid (a pro-apoptotic stimulus), are likely the GTPases involved in regulated cell death, while active Ras1 proteins, constitutively localized in mitochondria, might be involved in a pro-survival molecular machinery. Finally, by characterizing the gpa2Δ and cyr1Δ mutants, in which the cAMP/PKA pathway is compromised, we show that active mitochondrial Ras proteins promote apoptosis through the cAMP/PKA pathway.
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Affiliation(s)
- Barbara Bonomelli
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milan, Italy
| | - Stefano Busti
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milan, Italy
| | - Enzo Martegani
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milan, Italy
| | - Sonia Colombo
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milan, Italy
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Dillon M, Lopez A, Lin E, Sales D, Perets R, Jain P. Progress on Ras/MAPK Signaling Research and Targeting in Blood and Solid Cancers. Cancers (Basel) 2021; 13:cancers13205059. [PMID: 34680208 PMCID: PMC8534156 DOI: 10.3390/cancers13205059] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Revised: 09/30/2021] [Accepted: 10/06/2021] [Indexed: 12/18/2022] Open
Abstract
Simple Summary The Ras-Raf-MEK-ERK signaling pathway is responsible for regulating cell proliferation, differentiation, and survival. Overexpression and overactivation of members within the signaling cascade have been observed in many solid and blood cancers. Research often focuses on targeting the pathway to disrupt cancer initiation and progression. We aimed to provide an overview of the pathway’s physiologic role and regulation, interactions with other pathways involved in cancer development, and mutations that lead to malignancy. Several blood and solid cancers are analyzed to illustrate the impact of the pathway’s dysregulation, stemming from mutation or viral induction. Finally, we summarized different approaches to targeting the pathway and the associated novel treatments being researched or having recently achieved approval. Abstract The mitogen-activated protein kinase (MAPK) pathway, consisting of the Ras-Raf-MEK-ERK signaling cascade, regulates genes that control cellular development, differentiation, proliferation, and apoptosis. Within the cascade, multiple isoforms of Ras and Raf each display differences in functionality, efficiency, and, critically, oncogenic potential. According to the NCI, over 30% of all human cancers are driven by Ras genes. This dysfunctional signaling is implicated in a wide variety of leukemias and solid tumors, both with and without viral etiology. Due to the strong evidence of Ras-Raf involvement in tumorigenesis, many have attempted to target the cascade to treat these malignancies. Decades of unsuccessful experimentation had deemed Ras undruggable, but recently, the approval of Sotorasib as the first ever KRas inhibitor represents a monumental breakthrough. This advancement is not without novel challenges. As a G12C mutant-specific drug, it also represents the issue of drug target specificity within Ras pathway; not only do many drugs only affect single mutational profiles, with few pan-inhibitor exceptions, tumor genetic heterogeneity may give rise to drug-resistant profiles. Furthermore, significant challenges in targeting downstream Raf, especially the BRaf isoform, lie in the paradoxical activation of wild-type BRaf by BRaf mutant inhibitors. This literature review will delineate the mechanisms of Ras signaling in the MAPK pathway and its possible oncogenic mutations, illustrate how specific mutations affect the pathogenesis of specific cancers, and compare available and in-development treatments targeting the Ras pathway.
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Quadri R, Galli M, Galati E, Rotondo G, Gallo GR, Panigada D, Plevani P, Muzi-Falconi M. Haspin regulates Ras localization to promote Cdc24-driven mitotic depolarization. Cell Discov 2020; 6:42. [PMID: 32595981 PMCID: PMC7308332 DOI: 10.1038/s41421-020-0170-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Accepted: 04/10/2020] [Indexed: 11/08/2022] Open
Abstract
Cell polarization is of paramount importance for proliferation, differentiation, development, and it is altered during carcinogenesis. Polarization is a reversible process controlled by positive and negative feedback loops. How polarized factors are redistributed is not fully understood and is the focus of this work. In Saccharomyces cerevisiae, mutants defective in haspin kinase exhibit stably polarized landmarks and are sensitive to mitotic delays. Here, we report a new critical role for haspin in polarisome dispersion; failure to redistribute polarity factors, in turn, leads to nuclear segregation defects and cell lethality. We identified a mitotic role for GTP-Ras in regulating the local activation of the Cdc42 GTPase, resulting in its dispersal from the bud tip to a homogeneous distribution over the plasma membrane. GTP-Ras2 physically interacts with Cdc24 regulateing its mitotic distribution. Haspin is shown to promote a mitotic shift from a bud tip-favored to a homogenous PM fusion of Ras-containing vesicles. In absence of haspin, active Ras is not redistributed from the bud tip; Cdc24 remains hyperpolarized promoting the activity of Cdc42 at the bud tip, and the polarisome fails to disperse leading to erroneously positioned mitotic spindle, defective nuclear segregation, and cell death after mitotic delays. These findings describe new functions for key factors that modulate cell polarization and mitotic events, critical processes involved in development and tumorigenesis.
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Affiliation(s)
- Roberto Quadri
- Dipartimento di Bioscienze, Università degli Studi di Milano, Via Celoria 26, 20133 Milano, Italy
| | - Martina Galli
- Dipartimento di Bioscienze, Università degli Studi di Milano, Via Celoria 26, 20133 Milano, Italy
- Present Address: IFOM, Istituto FIRC di Oncologia Molecolare, Via Adamello 16, 20139 Milano, Italy
| | - Elena Galati
- Dipartimento di Bioscienze, Università degli Studi di Milano, Via Celoria 26, 20133 Milano, Italy
| | - Giuseppe Rotondo
- Dipartimento di Bioscienze, Università degli Studi di Milano, Via Celoria 26, 20133 Milano, Italy
| | - Guido Roberto Gallo
- Dipartimento di Bioscienze, Università degli Studi di Milano, Via Celoria 26, 20133 Milano, Italy
| | - Davide Panigada
- Dipartimento di Bioscienze, Università degli Studi di Milano, Via Celoria 26, 20133 Milano, Italy
| | - Paolo Plevani
- Dipartimento di Bioscienze, Università degli Studi di Milano, Via Celoria 26, 20133 Milano, Italy
| | - Marco Muzi-Falconi
- Dipartimento di Bioscienze, Università degli Studi di Milano, Via Celoria 26, 20133 Milano, Italy
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7
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Miller TE, Henkels KM, Huddleston M, Salisbury R, Hussain SM, Sasaki AT, Cho KJ. Depletion of phosphatidylinositol 4-phosphate at the Golgi translocates K-Ras to mitochondria. J Cell Sci 2019; 132:jcs.231886. [PMID: 31331963 DOI: 10.1242/jcs.231886] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Accepted: 07/12/2019] [Indexed: 01/05/2023] Open
Abstract
Ras proteins are small GTPases localized to the plasma membrane (PM), which regulate cellular proliferation, apoptosis and differentiation. After a series of post-translational modifications, H-Ras and N-Ras traffic to the PM from the Golgi via the classical exocytic pathway, but the exact mechanism of K-Ras trafficking to the PM from the ER is not fully characterized. ATP5G1 (also known as ATP5MC1) is one of the three proteins that comprise subunit c of the F 0 complex of the mitochondrial ATP synthase. In this study, we show that overexpression of the mitochondrial targeting sequence of ATP5G1 perturbs glucose metabolism, inhibits oncogenic K-Ras signaling, and redistributes phosphatidylserine (PtdSer) to mitochondria and other endomembranes, resulting in K-Ras translocation to mitochondria. Also, it depletes phosphatidylinositol 4-phosphate (PI4P) at the Golgi. Glucose supplementation restores PtdSer and K-Ras PM localization and PI4P at the Golgi. We further show that inhibition of the Golgi-localized PI4-kinases (PI4Ks) translocates K-Ras, and PtdSer to mitochondria and endomembranes, respectively. We conclude that PI4P at the Golgi regulates the PM localization of PtdSer and K-Ras.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Taylor E Miller
- Department of Biochemistry and Molecular Biology, Boonshoft School of Medicine, Wright State University, OH 45435, USA
| | - Karen M Henkels
- Department of Biochemistry and Molecular Biology, Boonshoft School of Medicine, Wright State University, OH 45435, USA
| | - Mary Huddleston
- Human Signatures Branch, Human-Centered ISR Division, Airman Systems Directorate, 711 Human Performance Wing, Air Force Research Laboratory, Wright Patterson Air Force Base, OH 45433, USA
| | - Richard Salisbury
- Human Signatures Branch, Human-Centered ISR Division, Airman Systems Directorate, 711 Human Performance Wing, Air Force Research Laboratory, Wright Patterson Air Force Base, OH 45433, USA
| | - Saber M Hussain
- Human Signatures Branch, Human-Centered ISR Division, Airman Systems Directorate, 711 Human Performance Wing, Air Force Research Laboratory, Wright Patterson Air Force Base, OH 45433, USA
| | - Atsuo T Sasaki
- Division of Hematology and Oncology, Department of Internal Medicine, University of Cincinnati, Cincinnati, OH 45267, USA
| | - Kwang-Jin Cho
- Department of Biochemistry and Molecular Biology, Boonshoft School of Medicine, Wright State University, OH 45435, USA
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8
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Koch B, Tucey TM, Lo TL, Novakovic S, Boag P, Traven A. The Mitochondrial GTPase Gem1 Contributes to the Cell Wall Stress Response and Invasive Growth of Candida albicans. Front Microbiol 2017; 8:2555. [PMID: 29326680 PMCID: PMC5742345 DOI: 10.3389/fmicb.2017.02555] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Accepted: 12/08/2017] [Indexed: 01/27/2023] Open
Abstract
The interactions of mitochondria with the endoplasmic reticulum (ER) are crucial for maintaining proper mitochondrial morphology, function and dynamics. This enables cells to utilize their mitochondria optimally for energy production and anabolism, and it further provides for metabolic control over developmental decisions. In fungi, a key mechanism by which ER and mitochondria interact is via a membrane tether, the protein complex ERMES (ER-Mitochondria Encounter Structure). In the model yeast Saccharomyces cerevisiae, the mitochondrial GTPase Gem1 interacts with ERMES, and it has been proposed to regulate its activity. Here we report on the first characterization of Gem1 in a human fungal pathogen. We show that in Candida albicans Gem1 has a dominant role in ensuring proper mitochondrial morphology, and our data is consistent with Gem1 working with ERMES in this role. Mitochondrial respiration and steady state cellular phospholipid homeostasis are not impacted by inactivation of GEM1 in C. albicans. There are two major virulence-related consequences of disrupting mitochondrial morphology by GEM1 inactivation: C. albicans becomes hypersusceptible to cell wall stress, and is unable to grow invasively. In the gem1Δ/Δ mutant, it is specifically the invasive capacity of hyphae that is compromised, not the ability to transition from yeast to hyphal morphology, and this phenotype is shared with ERMES mutants. As a consequence of the hyphal invasion defect, the gem1Δ/Δ mutant is drastically hypovirulent in the worm infection model. Activation of the mitogen activated protein (MAP) kinase Cek1 is reduced in the gem1Δ/Δ mutant, and this function could explain both the susceptibility to cell wall stress and lack of invasive growth. This result establishes a new, respiration-independent mechanism of mitochondrial control over stress signaling and hyphal functions in C. albicans. We propose that ER-mitochondria interactions and the ER-Mitochondria Organizing Network (ERMIONE) play important roles in adaptive responses in fungi, in particular cell surface-related mechanisms that drive invasive growth and stress responsive behaviors that support fungal pathogenicity.
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Affiliation(s)
- Barbara Koch
- Infection and Immunity Program and the Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
| | - Timothy M Tucey
- Infection and Immunity Program and the Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
| | - Tricia L Lo
- Infection and Immunity Program and the Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
| | - Stevan Novakovic
- Development and Stem Cells Program and the Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
| | - Peter Boag
- Development and Stem Cells Program and the Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
| | - Ana Traven
- Infection and Immunity Program and the Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
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9
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Eisenberg-Bord M, Schuldiner M. Mitochatting - If only we could be a fly on the cell wall. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2017; 1864:1469-1480. [PMID: 28433686 DOI: 10.1016/j.bbamcr.2017.04.012] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 01/07/2017] [Revised: 04/12/2017] [Accepted: 04/18/2017] [Indexed: 12/24/2022]
Abstract
Mitochondria, cellular metabolic hubs, perform many essential processes and are required for the production of metabolites such as ATP, iron-sulfur clusters, heme, amino acids and nucleotides. To fulfill their multiple roles, mitochondria must communicate with all other organelles to exchange small molecules, ions and lipids. Since mitochondria are largely excluded from vesicular trafficking routes, they heavily rely on membrane contact sites. Contact sites are areas of close proximity between organelles that allow efficient transfer of molecules, saving the need for slow and untargeted diffusion through the cytosol. More globally, multiple metabolic pathways require coordination between mitochondria and additional organelles and mitochondrial activity affects all other cellular entities and vice versa. Therefore, uncovering the different means of mitochondrial communication will allow us a better understanding of mitochondria and may illuminate disease processes that occur in the absence of proper cross-talk. In this review we focus on how mitochondria interact with all other organelles and emphasize how this communication is essential for mitochondrial and cellular homeostasis. This article is part of a Special Issue entitled: Membrane Contact Sites edited by Christian Ungermann and Benoit Kornmann.
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Affiliation(s)
- Michal Eisenberg-Bord
- Department of Molecular Genetics, Weizmann Institute of Science, 7610001 Rehovot, Israel
| | - Maya Schuldiner
- Department of Molecular Genetics, Weizmann Institute of Science, 7610001 Rehovot, Israel.
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10
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Multiple roles of a putative vacuolar protein sorting associated protein 74, FgVPS74, in the cereal pathogen Fusarium graminearum. J Microbiol 2015; 53:243-9. [DOI: 10.1007/s12275-015-5067-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Revised: 02/11/2015] [Accepted: 02/11/2015] [Indexed: 11/26/2022]
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11
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Intrinsically disordered cytoplasmic domains of two cytokine receptors mediate conserved interactions with membranes. Biochem J 2015; 468:495-506. [PMID: 25846210 DOI: 10.1042/bj20141243] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Accepted: 04/07/2015] [Indexed: 01/29/2023]
Abstract
Class 1 cytokine receptors regulate essential biological processes through complex intracellular signalling networks. However, the structural platform for understanding their functions is currently incomplete as structure-function studies of the intracellular domains (ICDs) are critically lacking. The present study provides the first comprehensive structural characterization of any cytokine receptor ICD and demonstrates that the human prolactin (PRL) receptor (PRLR) and growth hormone receptor (GHR) ICDs are intrinsically disordered throughout their entire lengths. We show that they interact specifically with hallmark lipids of the inner plasma membrane leaflet through conserved motifs resembling immuno receptor tyrosine-based activation motifs (ITAMs). However, contrary to the observations made for ITAMs, lipid association of the PRLR and GHR ICDs was shown to be unaccompanied by changes in transient secondary structure and independent of tyrosine phosphorylation. The results of the present study provide a new structural platform for studying class 1 cytokine receptors and may implicate the membrane as an active component regulating intracellular signalling.
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12
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Chauvin S, Sobel A. Neuronal stathmins: A family of phosphoproteins cooperating for neuronal development, plasticity and regeneration. Prog Neurobiol 2015; 126:1-18. [DOI: 10.1016/j.pneurobio.2014.09.002] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2014] [Revised: 09/23/2014] [Accepted: 09/29/2014] [Indexed: 02/06/2023]
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13
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Abstract
For centuries yeast species have been popular hosts for classical biotechnology processes, such as baking, brewing, and wine making, and more recently for recombinant proteins production, thanks to the advantages of unicellular organisms (i.e., ease of genetic manipulation and rapid growth) together with the ability to perform eukaryotic posttranslational modifications. Moreover, yeast cells have been used for few decades as a tool for identifying the genes and pathways involved in basic cellular processes such as the cell cycle, aging, and stress response. In the budding yeast S. cerevisiae the Ras/cAMP/PKA pathway is directly involved in the regulation of metabolism, cell growth, stress resistance, and proliferation in response to the availability of nutrients and in the adaptation to glucose, controlling cytosolic cAMP levels and consequently the cAMP-dependent protein kinase (PKA) activity. Moreover, Ras signalling has been identified in several pathogenic yeasts as a key controller for virulence, due to its involvement in yeast morphogenesis. Nowadays, yeasts are still useful for Ras-like proteins investigation, both as model organisms and as a test tube to study variants of heterologous Ras-like proteins.
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Affiliation(s)
- Renata Tisi
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milan, Italy
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14
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Hartmann M, Hemmerlin A, Gas-Pascual E, Gerber E, Tritsch D, Rohmer M, Bach TJ. The effect of MEP pathway and other inhibitors on the intracellular localization of a plasma membrane-targeted, isoprenylable GFP reporter protein in tobacco BY-2 cells. F1000Res 2013; 2:170. [PMID: 24555083 DOI: 10.12688/f1000research.2-170.v1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 08/01/2013] [Indexed: 11/20/2022] Open
Abstract
We have established anin vivovisualization system for the geranylgeranylation of proteins in a stably transformed tobacco BY-2 cell line, based on the expression of a dexamethasone-inducible GFP fused to the carboxy-terminal basic domain of the rice calmodulin CaM61, which naturally bears a CaaL geranylgeranylation motif (GFP-BD-CVIL). By using pathway-specific inhibitors it was demonstrated that inhibition of the methylerythritol phosphate (MEP) pathway with known inhibitors like oxoclomazone and fosmidomycin, as well as inhibition of the protein geranylgeranyltransferase type 1 (PGGT-1), shifted the localization of the GFP-BD-CVIL protein from the membrane to the nucleus. In contrast, the inhibition of the mevalonate (MVA) pathway with mevinolin did not affect the localization. During the present work, this test system has been used to examine the effect of newly designed inhibitors of the MEP pathway and inhibitors of sterol biosynthesis such as squalestatin, terbinafine and Ro48-8071. In addition, we also studied the impact of different post-prenylation inhibitors or those suspected to affect the transport of proteins to the plasma membrane on the localization of the geranylgeranylable fusion protein GFP-BD-CVIL.
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Affiliation(s)
- Michael Hartmann
- Département Réseaux Métaboliques, Institut de Biologie Moléculaire des Plantes, CNRS UPR 2357, Université de Strasbourg, F-67083 Strasbourg, France ; Current address: Institute of Biological Chemistry, Washington State University, Pullman WA, 99164-6340, USA
| | - Andrea Hemmerlin
- Département Réseaux Métaboliques, Institut de Biologie Moléculaire des Plantes, CNRS UPR 2357, Université de Strasbourg, F-67083 Strasbourg, France
| | - Elisabet Gas-Pascual
- Département Réseaux Métaboliques, Institut de Biologie Moléculaire des Plantes, CNRS UPR 2357, Université de Strasbourg, F-67083 Strasbourg, France ; Current address: Department of Horticulture and Crop Science, Ohio State University, Wooster OH, 44691, USA
| | - Esther Gerber
- Département Réseaux Métaboliques, Institut de Biologie Moléculaire des Plantes, CNRS UPR 2357, Université de Strasbourg, F-67083 Strasbourg, France ; Current address: Deinove SA, F-34830 Clapiers, France
| | - Denis Tritsch
- UMR 7177 CNRS, Laboratoire de Chimie et Biochimie des Microorganismes, Institut de Chimie de Strasbourg, Université de Strasbourg, F-67008 Strasbourg, France
| | - Michel Rohmer
- UMR 7177 CNRS, Laboratoire de Chimie et Biochimie des Microorganismes, Institut de Chimie de Strasbourg, Université de Strasbourg, F-67008 Strasbourg, France
| | - Thomas J Bach
- Département Réseaux Métaboliques, Institut de Biologie Moléculaire des Plantes, CNRS UPR 2357, Université de Strasbourg, F-67083 Strasbourg, France
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15
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Hartmann M, Hemmerlin A, Gas-Pascual E, Gerber E, Tritsch D, Rohmer M, Bach TJ. The effect of MEP pathway and other inhibitors on the intracellular localization of a plasma membrane-targeted, isoprenylable GFP reporter protein in tobacco BY-2 cells. F1000Res 2013; 2:170. [PMID: 24555083 PMCID: PMC3886798 DOI: 10.12688/f1000research.2-170.v2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 11/12/2013] [Indexed: 11/20/2022] Open
Abstract
We have established an
in vivo visualization system for the geranylgeranylation of proteins in a stably transformed tobacco BY-2 cell line, based on the expression of a dexamethasone-inducible GFP fused to the carboxy-terminal basic domain of the rice calmodulin CaM61, which naturally bears a CaaL geranylgeranylation motif (GFP-BD-CVIL). By using pathway-specific inhibitors it was demonstrated that inhibition of the methylerythritol phosphate (MEP) pathway with known inhibitors like oxoclomazone and fosmidomycin, as well as inhibition of the protein geranylgeranyltransferase type 1 (PGGT-1), shifted the localization of the GFP-BD-CVIL protein from the membrane to the nucleus. In contrast, the inhibition of the mevalonate (MVA) pathway with mevinolin did not affect the localization. During the present work, this test system has been used to examine the effect of newly designed inhibitors of the MEP pathway and inhibitors of sterol biosynthesis such as squalestatin, terbinafine and Ro48-8071. In addition, we also studied the impact of different post-prenylation inhibitors or those suspected to affect the transport of proteins to the plasma membrane on the localization of the geranylgeranylable fusion protein GFP-BD-CVIL.
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Affiliation(s)
- Michael Hartmann
- Département Réseaux Métaboliques, Institut de Biologie Moléculaire des Plantes, CNRS UPR 2357, Université de Strasbourg, F-67083 Strasbourg, France ; Current address: Institute of Biological Chemistry, Washington State University, Pullman WA, 99164-6340, USA
| | - Andrea Hemmerlin
- Département Réseaux Métaboliques, Institut de Biologie Moléculaire des Plantes, CNRS UPR 2357, Université de Strasbourg, F-67083 Strasbourg, France
| | - Elisabet Gas-Pascual
- Département Réseaux Métaboliques, Institut de Biologie Moléculaire des Plantes, CNRS UPR 2357, Université de Strasbourg, F-67083 Strasbourg, France ; Current address: Department of Horticulture and Crop Science, Ohio State University, Wooster OH, 44691, USA
| | - Esther Gerber
- Département Réseaux Métaboliques, Institut de Biologie Moléculaire des Plantes, CNRS UPR 2357, Université de Strasbourg, F-67083 Strasbourg, France ; Current address: Deinove SA, F-34830 Clapiers, France
| | - Denis Tritsch
- UMR 7177 CNRS, Laboratoire de Chimie et Biochimie des Microorganismes, Institut de Chimie de Strasbourg, Université de Strasbourg, F-67008 Strasbourg, France
| | - Michel Rohmer
- UMR 7177 CNRS, Laboratoire de Chimie et Biochimie des Microorganismes, Institut de Chimie de Strasbourg, Université de Strasbourg, F-67008 Strasbourg, France
| | - Thomas J Bach
- Département Réseaux Métaboliques, Institut de Biologie Moléculaire des Plantes, CNRS UPR 2357, Université de Strasbourg, F-67083 Strasbourg, France
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16
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Abstract
Oncogenic mutant K-Ras is highly prevalent in multiple human tumors. Despite significant efforts to directly target Ras activity, no K-Ras-specific inhibitors have been developed and taken into the clinic. Since Ras proteins must be anchored to the inner leaflet of the plasma membrane (PM) for full biological activity, we devised a high-content screen to identify molecules with ability to displace K-Ras from the PM. Here we summarize the biochemistry and biology of three classes of compound identified by this screening method that inhibit K-Ras PM targeting: staurosporine and analogs, fendiline, and metformin. All three classes of compound significantly abrogate cell proliferation and Ras signaling in K-Ras-transformed cancer cells. Taken together, these studies provide an important proof of concept that blocking PM localization of K-Ras is a tractable therapeutic target.
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Affiliation(s)
- Kwang-Jin Cho
- Department of Integrative Biology and Pharmacology, The University of Texas Medical School at Houston, Houston, Texas, USA
| | - Dharini van der Hoeven
- Department of Diagnostic and Biomedical Sciences, The University of Texas School of Dentistry at Houston, Houston, Texas, USA
| | - John F Hancock
- Department of Integrative Biology and Pharmacology, The University of Texas Medical School at Houston, Houston, Texas, USA.
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17
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Leadsham JE, Sanders G, Giannaki S, Bastow EL, Hutton R, Naeimi WR, Breitenbach M, Gourlay CW. Loss of cytochrome c oxidase promotes RAS-dependent ROS production from the ER resident NADPH oxidase, Yno1p, in yeast. Cell Metab 2013; 18:279-86. [PMID: 23931758 DOI: 10.1016/j.cmet.2013.07.005] [Citation(s) in RCA: 118] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2013] [Revised: 05/14/2013] [Accepted: 06/25/2013] [Indexed: 10/26/2022]
Abstract
Many disease states, including the aging process, are associated with the accumulation of mitochondria harboring respiratory dysfunction. Mitochondrial dysfunction is often accompanied by increased ROS levels that can contribute to cellular dysfunction and disease etiology. Here we use the model eukaryote S. cerevisiae to investigate whether reduced cytochrome c oxidase (COX) activity, commonly reported in aging organisms and associated with neurodegenerative disorders, leads to ROS production from mitochondria. We provide evidence that although reduced COX complex activity correlates with ROS accumulation, mitochondria are not the major production center. Instead we show that COX-deficient mitochondria activate Ras upon their outer membrane that establishes a pro-ROS accumulation environment by suppressing antioxidant defenses and the ERAD-mediated turnover of the ER-localized NADPH oxidase Yno1p. Our data suggest that dysfunctional mitochondria can serve as a signaling platform to promote the loss of redox homeostasis, ROS accumulation, and accelerate aging in yeast.
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18
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Defects associated with mitochondrial DNA damage can be mitigated by increased vacuolar pH in Saccharomyces cerevisiae. Genetics 2013; 194:285-90. [PMID: 23502676 DOI: 10.1534/genetics.113.149708] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
While searching for mutations that alleviate detrimental effects of mitochondrial DNA (mtDNA) damage, we found that disrupting vacuolar biogenesis permitted survival of a sensitized yeast background after mitochondrial genome loss. Furthermore, elevating vacuolar pH increases proliferation after mtDNA deletion and reverses the protein import defect of mitochondria lacking DNA.
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19
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Qattan AT, Radulovic M, Crawford M, Godovac-Zimmermann J. Spatial distribution of cellular function: the partitioning of proteins between mitochondria and the nucleus in MCF7 breast cancer cells. J Proteome Res 2012; 11:6080-101. [PMID: 23051583 PMCID: PMC4261608 DOI: 10.1021/pr300736v] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Concurrent proteomics analysis of the nuclei and mitochondria of MCF7 breast cancer cells identified 985 proteins (40% of all detected proteins) present in both organelles. Numerous proteins from all five complexes involved in oxidative phosphorylation (e.g., NDUFA5, NDUFB10, NDUFS1, NDUF2, SDHA, UQRB, UQRC2, UQCRH, COX5A, COX5B, MT-CO2, ATP5A1, ATP5B, ATP5H, etc.), from the TCA-cycle (DLST, IDH2, IDH3A, OGDH, SUCLAG2, etc.), and from glycolysis (ALDOA, ENO1, FBP1, GPI, PGK1, TALDO1, etc.) were distributed to both the nucleus and mitochondria. In contrast, proteins involved in nuclear/mitochondrial RNA processing/translation and Ras/Rab signaling showed different partitioning patterns. The identity of the OxPhos, TCA-cycle, and glycolysis proteins distributed to both the nucleus and mitochondria provides evidence for spatio-functional integration of these processes over the two different subcellular organelles. We suggest that there are unrecognized aspects of functional coordination between the nucleus and mitochondria, that integration of core functional processes via wide subcellular distribution of constituent proteins is a common characteristic of cells, and that subcellular spatial integration of function may be a vital aspect of cancer.
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Affiliation(s)
- Amal T. Qattan
- Proteomics and Molecular Cell Dynamics, Division of Medicine, School of Life and Medical Sciences, University College London, Royal Free Campus, Rowland Hill Street NW3 2PF, United Kingdom
| | - Marko Radulovic
- Proteomics and Molecular Cell Dynamics, Division of Medicine, School of Life and Medical Sciences, University College London, Royal Free Campus, Rowland Hill Street NW3 2PF, United Kingdom
| | - Mark Crawford
- Proteomics and Molecular Cell Dynamics, Division of Medicine, School of Life and Medical Sciences, University College London, Royal Free Campus, Rowland Hill Street NW3 2PF, United Kingdom
| | - Jasminka Godovac-Zimmermann
- Proteomics and Molecular Cell Dynamics, Division of Medicine, School of Life and Medical Sciences, University College London, Royal Free Campus, Rowland Hill Street NW3 2PF, United Kingdom
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20
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Fendiline inhibits K-Ras plasma membrane localization and blocks K-Ras signal transmission. Mol Cell Biol 2012; 33:237-51. [PMID: 23129805 DOI: 10.1128/mcb.00884-12] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Ras proteins regulate signaling pathways important for cell growth, differentiation, and survival. Oncogenic mutant Ras proteins are commonly expressed in human tumors, with mutations of the K-Ras isoform being most prevalent. To be active, K-Ras must undergo posttranslational processing and associate with the plasma membrane. We therefore devised a high-content screening assay to search for inhibitors of K-Ras plasma membrane association. Using this assay, we identified fendiline, an L-type calcium channel blocker, as a specific inhibitor of K-Ras plasma membrane targeting with no detectable effect on the localization of H- and N-Ras. Other classes of L-type calcium channel blockers did not mislocalize K-Ras, suggesting a mechanism that is unrelated to calcium channel blockade. Fendiline did not inhibit K-Ras posttranslational processing but significantly reduced nanoclustering of K-Ras and redistributed K-Ras from the plasma membrane to the endoplasmic reticulum (ER), Golgi apparatus, endosomes, and cytosol. Fendiline significantly inhibited signaling downstream of constitutively active K-Ras and endogenous K-Ras signaling in cells transformed by oncogenic H-Ras. Consistent with these effects, fendiline blocked the proliferation of pancreatic, colon, lung, and endometrial cancer cell lines expressing oncogenic mutant K-Ras. Taken together, these results suggest that inhibitors of K-Ras plasma membrane localization may have utility as novel K-Ras-specific anticancer therapeutics.
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21
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Broggi S, Martegani E, Colombo S. Live-cell imaging of endogenous Ras-GTP shows predominant Ras activation at the plasma membrane and in the nucleus in Saccharomyces cerevisiae. Int J Biochem Cell Biol 2012; 45:384-94. [PMID: 23127800 DOI: 10.1016/j.biocel.2012.10.013] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2012] [Revised: 10/02/2012] [Accepted: 10/25/2012] [Indexed: 10/27/2022]
Abstract
Ras proteins function as a point of convergence for different signalling pathways in eukaryotes and are involved in many cellular responses; their different subcellular locations could regulate distinct functions. To investigate the localization of active Ras in vivo in Saccharomyces cerevisiae, we expressed a probe consisting of a GFP fusion with a trimeric Ras binding domain of Raf1 (eGFP-RBD3), which binds Ras-GTP with a much higher affinity than Ras-GDP. Our results show that in wild type cells active Ras accumulates mainly at the plasma membrane and in the nucleus during growth on medium containing glucose, while it accumulates mainly in mitochondria in wild type glucose-starved cells and relocalizes to the plasma membrane and to the nucleus upon addition of this sugar. A similar pattern is observed in a strain deleted in the CYR1 gene indicating that the absence of adenylate cyclase does not impair the localization of Ras-GTP. Remarkably, in a gpa2Δ, but not in a gpr1Δ mutant, active Ras accumulates in internal membranes and mitochondria, both when cells are growing on glucose medium or are starved, indicating that Gpa2, but not Gpr1 is required for the recruitment of Ras-GTP at the plasma membrane and in the nucleus. Moreover, deletion of both HXK1 and HXK2 also causes a mitochondrial localization of the probe, which relocalizes to the plasma membrane and to the nucleus upon expression of HXK2 on a centromeric plasmid, suggesting that this kinase is involved in the proper localization of active Ras.
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Affiliation(s)
- Serena Broggi
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milan, Italy
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22
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Cho KJ, Park JH, Piggott AM, Salim AA, Gorfe AA, Parton RG, Capon RJ, Lacey E, Hancock JF. Staurosporines disrupt phosphatidylserine trafficking and mislocalize Ras proteins. J Biol Chem 2012; 287:43573-84. [PMID: 23124205 DOI: 10.1074/jbc.m112.424457] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Oncogenic mutant Ras is frequently expressed in human cancers, but no anti-Ras drugs have been developed. Since membrane association is essential for Ras biological activity, we developed a high content assay for inhibitors of Ras plasma membrane localization. We discovered that staurosporine and analogs potently inhibit Ras plasma membrane binding by blocking endosomal recycling of phosphatidylserine, resulting in redistribution of phosphatidylserine from plasma membrane to endomembrane. Staurosporines are more active against K-Ras than H-Ras. K-Ras is displaced to endosomes and undergoes proteasomal-independent degradation, whereas H-Ras redistributes to the Golgi and is not degraded. K-Ras nanoclustering on the plasma membrane is also inhibited. Ras mislocalization does not correlate with protein kinase C inhibition or induction of apoptosis. Staurosporines selectively abrogate K-Ras signaling and proliferation of K-Ras-transformed cells. These results identify staurosporines as novel inhibitors of phosphatidylserine trafficking, yield new insights into the role of phosphatidylserine and electrostatics in Ras plasma membrane targeting, and validate a new target for anti-Ras therapeutics.
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Affiliation(s)
- Kwang-jin Cho
- Department of Integrative Biology and Pharmacology, The University of Texas Medical School-Houston, Houston, Texas 77030, USA
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23
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Abstract
Availability of key nutrients, such as sugars, amino acids, and nitrogen compounds, dictates the developmental programs and the growth rates of yeast cells. A number of overlapping signaling networks--those centered on Ras/protein kinase A, AMP-activated kinase, and target of rapamycin complex I, for instance--inform cells on nutrient availability and influence the cells' transcriptional, translational, posttranslational, and metabolic profiles as well as their developmental decisions. Here I review our current understanding of the structures of the networks responsible for assessing the quantity and quality of carbon and nitrogen sources. I review how these signaling pathways impinge on transcriptional, metabolic, and developmental programs to optimize survival of cells under different environmental conditions. I highlight the profound knowledge we have gained on the structure of these signaling networks but also emphasize the limits of our current understanding of the dynamics of these signaling networks. Moreover, the conservation of these pathways has allowed us to extrapolate our finding with yeast to address issues of lifespan, cancer metabolism, and growth control in more complex organisms.
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Affiliation(s)
- James R Broach
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA.
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24
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HIV Assembly and Budding: Ca(2+) Signaling and Non-ESCRT Proteins Set the Stage. Mol Biol Int 2012; 2012:851670. [PMID: 22761998 PMCID: PMC3384956 DOI: 10.1155/2012/851670] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Accepted: 03/26/2012] [Indexed: 12/16/2022] Open
Abstract
More than a decade has elapsed since the link between the endosomal sorting complex required for transport (ESCRT) machinery and HIV-1 protein trafficking and budding was first identified. L domains in HIV-1 Gag mediate recruitment of ESCRT which function in bud abscission releasing the viral particle from the host cell. Beyond virus budding, the ESCRT machinery is also involved in the endocytic pathway, cytokinesis, and autophagy. In the past few years, the number of non-ESCRT host proteins shown to be required in the assembly process has also grown. In this paper, we highlight the role of recently identified cellular factors that link ESCRT machinery to calcium signaling machinery and we suggest that this liaison contributes to setting the stage for productive ESCRT recruitment and mediation of abscission. Parallel paradigms for non-ESCRT roles in virus budding and cytokinesis will be discussed.
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25
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Belotti F, Tisi R, Paiardi C, Rigamonti M, Groppi S, Martegani E. Localization of Ras signaling complex in budding yeast. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1823:1208-16. [PMID: 22575457 DOI: 10.1016/j.bbamcr.2012.04.016] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2011] [Revised: 04/26/2012] [Accepted: 04/30/2012] [Indexed: 10/28/2022]
Abstract
In Saccharomyces cerevisiae, cAMP/pKA pathway plays a major role in metabolism, stress resistance and proliferation control. cAMP is produced by adenylate cyclase, which is activated both by Gpr1/Gpa2 system and Ras proteins, regulated by Cdc25/Sdc25 guanine exchange factors and Ira GTPase activator proteins. Recently, both Ras2 and Cdc25 RasGEF were reported to localize not only in plasma membrane but also in internal membranes. Here, the subcellular localization of Ras signaling complex proteins was investigated both by fluorescent tagging and by biochemical cell membrane fractionation on sucrose gradients. Although a consistent minor fraction of Ras signaling complex components was found in plasma membrane during exponential growth on glucose, Cdc25 appears to localize mainly on ER membranes, while Ira2 and Cyr1 are also significantly present on mitochondria. Moreover, PKA Tpk1 catalytic subunit overexpression induces Ira2 protein to move from mitochondria to ER membranes. These data confirm the hypothesis that different branches of Ras signaling pathways could involve different subcellular compartments, and that relocalization of Ras signaling complex components is subject to PKA control.
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Affiliation(s)
- Fiorella Belotti
- Department of Biotechnology and Biosciences, Umiversity of Milano-Bicocca, Milan, Italy
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26
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Marshall PA, Netzel N, Guintchev JW. Assessing compensation for loss of vacuolar function in Saccharomyces cerevisiae. Can J Microbiol 2012; 58:132-44. [PMID: 22260156 DOI: 10.1139/w11-114] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We analyzed how Saccharomyces cerevisiae cells compensate for the lack of a functional vacuole, an acidic membrane-bound degradative and ion storage compartment. We hypothesized that cells lacking a functional vacuole would compensate for the loss of the functions of the vacuole by altering gene expression and (or) metabolic flux. We used gene expression profiling and Biolog phenotype microarray analysis to determine the compensatory mechanisms of cells lacking vacuolar function. In steady state, vps33 and vps41 cells changed the transcriptional profile of some genes, but no complete pathways were upregulated or downregulated. We treated vps41 cells with calcium to tease out cellular compensation for loss of vacuole function under ionic stress; however, changes in gene expression were not utilized to compensate for loss of vacuole function under stress either, as genes whose transcriptional profiles were changed did not function together in any one cellular process. Phenotype microarray analysis indicated that logarithmically growing vps33 or vps41 cells did not seem to compensate for loss of vacuolar function but instead demonstrated additional pleiotropic phenotypes due to the function of the vacuole. Under rich media conditions, yeast utilize the vacuole to regulate stress, ion response, and peptide degradation. However, loss of the vacuole does not lead to observable compensation mechanisms.
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Affiliation(s)
- Pamela A Marshall
- Division of Mathematical and Natural Sciences, New College of Interdisciplinary Arts and Sciences, Arizona State University, Phoenix, AZ 85069, USA.
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27
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Abstract
S-palmitoylation describes the reversible attachment of fatty acids (predominantly palmitate) onto cysteine residues via a labile thioester bond. This posttranslational modification impacts protein functionality by regulating membrane interactions, intracellular sorting, stability, and membrane micropatterning. Several recent findings have provided a tantalizing insight into the regulation and spatiotemporal dynamics of protein palmitoylation. In mammalian cells, the Golgi has emerged as a possible super-reaction center for the palmitoylation of peripheral membrane proteins, whereas palmitoylation reactions on post-Golgi compartments contribute to the regulation of specific substrates. In addition to palmitoylating and depalmitoylating enzymes, intracellular palmitoylation dynamics may also be controlled through interplay with distinct posttranslational modifications, such as phosphorylation and nitrosylation.
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Affiliation(s)
- Christine Salaun
- Institut National de la Santé et de la Recherche Médicale U845, Faculte de Medecine Paris Descartes, 75730 Paris, Cedex 15, France
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28
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Manandhar SP, Hildebrandt ER, Jacobsen WH, Santangelo GM, Schmidt WK. Chemical inhibition of CaaX protease activity disrupts yeast Ras localization. Yeast 2010; 27:327-43. [PMID: 20162532 DOI: 10.1002/yea.1756] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Proteins possessing a C-terminal CaaX motif, such as the Ras GTPases, undergo extensive post-translational modification that includes attachment of an isoprenoid lipid, proteolytic processing and carboxylmethylation. Inhibition of the enzymes involved in these processes is considered a cancer-therapeutic strategy. We previously identified nine in vitro inhibitors of the yeast CaaX protease Rce1p in a chemical library screen (Manandhar et al., 2007). Here, we demonstrate that these agents disrupt the normal plasma membrane distribution of yeast GFP-Ras reporters in a manner that pharmacologically phenocopies effects observed upon genetic loss of CaaX protease function. Consistent with Rce1p being the in vivo target of the inhibitors, we observe that compound-induced delocalization is suppressed by increasing the gene dosage of RCE1. Moreover, we observe that Rce1p biochemical activity associated with inhibitor-treated cells is inversely correlated with compound dose. Genetic loss of CaaX proteolysis results in mistargeting of GFP-Ras2p to subcellular foci that are positive for the endoplasmic reticulum marker Sec63p. Pharmacological inhibition of CaaX protease activity also delocalizes GFP-Ras2p to foci, but these foci are not as strongly positive for Sec63p. Lastly, we demonstrate that heterologously expressed human Rce1p can mediate proper targeting of yeast Ras and that its activity can also be perturbed by some of the above inhibitors. Together, these results indicate that disrupting the proteolytic modification of Ras GTPases impacts their in vivo trafficking.
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Affiliation(s)
- Surya P Manandhar
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
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29
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Vinnakota KC, Mitchell DA, Deschenes RJ, Wakatsuki T, Beard DA. Analysis of the diffusion of Ras2 in Saccharomyces cerevisiae using fluorescence recovery after photobleaching. Phys Biol 2010; 7:026011. [PMID: 20526029 DOI: 10.1088/1478-3975/7/2/026011] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Binding, lateral diffusion and exchange are fundamental dynamic processes involved in protein association with cellular membranes. In this study, we developed numerical simulations of lateral diffusion and exchange of fluorophores in membranes with arbitrary bleach geometry and exchange of the membrane-localized fluorophore with the cytosol during fluorescence recovery after photobleaching (FRAP) experiments. The model simulations were used to design FRAP experiments with varying bleach region sizes on plasma membrane-localized wild-type GFP-Ras2 with a dual lipid anchor and mutant GFP-Ras2C318S with a single lipid anchor in live yeast cells to investigate diffusional mobility and the presence of any exchange processes operating in the time scale of our experiments. Model parameters estimated using data from FRAP experiments with a 1 microm x 1 microm bleach region-of-interest (ROI) and a 0.5 microm x 0.5 microm bleach ROI showed that GFP-Ras2, single or dual lipid modified, diffuses as single species with no evidence of exchange with a cytoplasmic pool. This is the first report of Ras2 mobility in the yeast plasma membrane. The methods developed in this study are generally applicable for studying diffusion and exchange of membrane-associated fluorophores using FRAP on commercial confocal laser scanning microscopes.
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Affiliation(s)
- Kalyan C Vinnakota
- Biotechnology and Bioengineering Center, Medical College of Wisconsin, Milwaukee, WI 53226, USA
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30
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Du W, Ayscough KR. Methyl beta-cyclodextrin reduces accumulation of reactive oxygen species and cell death in yeast. Free Radic Biol Med 2009; 46:1478-87. [PMID: 19272445 DOI: 10.1016/j.freeradbiomed.2009.02.032] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2008] [Revised: 02/20/2009] [Accepted: 02/23/2009] [Indexed: 01/10/2023]
Abstract
Stabilized F-actin structures have been shown to be detrimental to both mammalian and yeast cells. In yeast, stabilization of actin caused by addition of jasplakinolide, by point mutations in the act1 gene, or by deletion of certain genes that regulate F-actin leads to cell death with hallmarks of apoptosis. In particular, there is an elevation in the levels of reactive oxygen species, and we have shown the importance of the Ras/cAMP pathway for this effect. Here we show that in yeast cells deleted for end3, which functions to regulate actin organization during endocytosis, treatment of cells with methyl beta-cyclodextrin reduces levels of reactive oxygen species and inhibits cell death progression. Methyl beta-cyclodextrin is widely used to disrupt lipid rafts that contain cholesterol. The mechanism through which the rescue is achieved was investigated and we demonstrate that methyl beta-cyclodextrin reduces accumulation of Ras2 at the plasma membrane in Deltaend3 cells. We use FRAP and live cell imaging to determine the possible mechanism through which methyl beta-cyclodextrin functions to elicit this effect on Ras2 localization. Finally, we demonstrate that addition of methyl beta-cyclodextrin to wild-type cells can act to protect cells from acute oxidative stress caused by addition of hydrogen peroxide.
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Affiliation(s)
- Wei Du
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK
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31
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Abstract
Differential subcellular compartmentalization of the three main Ras isoforms (H-Ras, N-Ras and K-Ras) is believed to underlie their biological differences. Modulatable interactions between cellular membranes and Ras C-terminal hypervariable region motifs determine differences in trafficking and the relative proportions of each isoform in cell-surface signalling nanoclusters and intracellular endoplasmic reticulum/Golgi, endosomal and mitochondrial compartments. Ras regulators, effectors and scaffolds are also differentially distributed, potentially enabling preferential coupling to specific signalling pathways in each subcellular location. Here we summarize the mechanisms underlying compartment-specific Ras signalling and the outputs generated.
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32
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Leadsham JE, Miller K, Ayscough KR, Colombo S, Martegani E, Sudbery P, Gourlay CW. Whi2p links nutritional sensing to actin-dependent Ras-cAMP-PKA regulation and apoptosis in yeast. J Cell Sci 2009; 122:706-15. [PMID: 19208759 DOI: 10.1242/jcs.042424] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Elucidating the mechanisms by which eukaryotic cells coordinate environmental signals with intracellular ;fate' decisions, such as apoptosis, remains one of the important challenges facing cell biologists. It has recently emerged that the dynamic nature of the actin cytoskeleton is an important factor in the linkage of sensation of extracellular stimuli to signalling mechanisms that regulate programmed cell death. In yeast, actin has been shown to play a role in the regulation of apoptosis as cells prepare themselves for quiescence in the face of nutritional exhaustion, by facilitating the shutdown of Ras-cAMP-PKA pathway activity. Here, we demonstrate that the loss of Whi2p function, a protein known to influence cell cycle exit under conditions of nutritional stress, leads to cell death in yeast that displays the hallmarks of actin-mediated apoptosis. We show that actin-mediated apoptosis occurs as a result of inappropriate Ras-cAMP-PKA activity in Deltawhi2 cells. Cells lacking Whi2p function exhibit an aberrant accumulation of activated Ras2 at the mitochondria in response to nutritional depletion. This study provides evidence that the shutdown of cAMP-PKA signalling activity in wild-type cells involves Whi2p-dependent targeting of Ras2p to the vacuole for proteolysis. We also demonstrate for the first time that Whi2p-dependent regulation of cAMP-PKA signalling plays a physiological role in the differentiation of yeast colonies by facilitating elaboration of distinct zones of cell death.
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Affiliation(s)
- Jane E Leadsham
- Department of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, UK
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Greaves J, Prescott GR, Gorleku OA, Chamberlain LH. The fat controller: roles of palmitoylation in intracellular protein trafficking and targeting to membrane microdomains (Review). Mol Membr Biol 2008; 26:67-79. [PMID: 19115144 DOI: 10.1080/09687680802620351] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The attachment of palmitic acid to the amino acid cysteine via thioester linkage (S-palmitoylation) is a common post-translational modification of eukaryotic proteins. In this review, we discuss the role of palmitoylation as a versatile protein sorting signal, regulating protein trafficking between distinct intracellular compartments and the micro-localization of proteins within membranes.
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Affiliation(s)
- Jennifer Greaves
- The Centre for Integrative Physiology, School of Biomedical Sciences, University of Edinburgh, Edinburgh, UK
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34
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Henis YI, Hancock JF, Prior IA. Ras acylation, compartmentalization and signaling nanoclusters (Review). Mol Membr Biol 2008; 26:80-92. [PMID: 19115142 DOI: 10.1080/09687680802649582] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Ras proteins have become paradigms for isoform- and compartment-specific signaling. Recent work has shown that Ras isoforms are differentially distributed within cell surface signaling nanoclusters and on endomembranous compartments. The critical feature regulating Ras protein localization and isoform-specific functions is the C-terminal hypervariable region (HVR). In this review we discuss the differential post-translational modifications and reversible targeting functions of Ras isoform HVR motifs. We describe how compartmentalized Ras signaling has specific functional consequences and how cell surface signaling nanoclusters generate precise signaling outputs.
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Affiliation(s)
- Yoav I Henis
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
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Tisi R, Belotti F, Paiardi C, Brunetti F, Martegani E. The budding yeast RasGEF Cdc25 reveals an unexpected nuclear localization. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2008; 1783:2363-74. [DOI: 10.1016/j.bbamcr.2008.09.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2008] [Revised: 09/10/2008] [Accepted: 09/10/2008] [Indexed: 11/26/2022]
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36
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Zhuravliova E, Barbakadze T, Narmania N, Sepashvili M, Mikeladze DG. Hypoinsulinemia alleviates the GRF1/Ras/Akt anti-apoptotic pathway and induces alterations of mitochondrial ras trafficking in neuronal cells. Neurochem Res 2008; 34:1076-82. [PMID: 19002579 DOI: 10.1007/s11064-008-9877-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/23/2008] [Indexed: 02/04/2023]
Abstract
Recent observations have established that interruption of insulin production causes deficits in learning and memory formation. We have studied the mechanism of insulin's neuroprotective effect on primary neuronal cells and in streptozotocin (STZ)-induced diabetic rat brain. We have found that in hippocampal neuronal cells insulin increases the content of farnesylated Ras and phosphorylated form of Akt. Besides, the treatment of cells by insulin leads to the activation of mitochondrial cytochrome oxidase, which is inhibited by manumycin, a farnesyltransferase inhibitor. During experimental diabetes, the content of membrane-bound GRF1 was decreased in rat hippocampus that was correlated with the reduction in mitochondrial Ras and phosphorylated forms of Akt. This redistribution in Ras-GRF system was accompanied by the alteration in the activities of CREB, NF-kB (p65) and c-Rel transcription factors. We have proposed that hypoinsulinemia induces the inhibition of Ras signalling in the neuronal cells additionally by abnormality of Ras trafficking into mitochondria.
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Affiliation(s)
- E Zhuravliova
- Department of Biochemistry, I. Beritashvili Institute of Physiology, Tbilisi, Georgia
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37
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Maynard TM, Meechan DW, Dudevoir ML, Gopalakrishna D, Peters AZ, Heindel CC, Sugimoto TJ, Wu Y, Lieberman JA, Lamantia AS. Mitochondrial localization and function of a subset of 22q11 deletion syndrome candidate genes. Mol Cell Neurosci 2008; 39:439-51. [PMID: 18775783 DOI: 10.1016/j.mcn.2008.07.027] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2007] [Revised: 05/12/2008] [Accepted: 07/30/2008] [Indexed: 10/21/2022] Open
Abstract
Six genes in the 1.5 Mb region of chromosome 22 deleted in DiGeorge/22q11 deletion syndrome-Mrpl40, Prodh, Slc25a1, Txnrd2, T10, and Zdhhc8-encode mitochondrial proteins. All six genes are expressed in the brain, and maximal expression coincides with peak forebrain synaptogenesis shortly after birth. Furthermore, their protein products are associated with brain mitochondria, including those in synaptic terminals. Among the six, only Zddhc8 influences mitochondria-regulated apoptosis when overexpressed, and appears to interact biochemically with established mitochondrial proteins. Zdhhc8 has an apparent interaction with Uqcrc1, a component of mitochondrial complex III. The two proteins are coincidently expressed in pre-synaptic processes; however, Zdhhc8 is more frequently seen in glutamatergic terminals. 22q11 deletion may alter metabolic properties of cortical mitochondria during early post-natal life, since expression complex III components, including Uqcrc1, is significantly increased at birth in a mouse model of 22q11 deletion, and declines to normal values in adulthood. Our results suggest that altered dosage of one, or several 22q11 mitochondrial genes, particularly during early post-natal cortical development, may disrupt neuronal metabolism or synaptic signaling.
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Affiliation(s)
- T M Maynard
- Department of Cell and Molecular Physiology, The University of North Carolina School of Medicine, Chapel Hill, NC 27599-7545, USA
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Davis-Hanna A, Piispanen AE, Stateva LI, Hogan DA. Farnesol and dodecanol effects on the Candida albicans Ras1-cAMP signalling pathway and the regulation of morphogenesis. Mol Microbiol 2008; 67:47-62. [PMID: 18078440 DOI: 10.1111/j.1365-2958.2007.06013.x] [Citation(s) in RCA: 196] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Candida albicans hypha formation which has been stimulated via the Ras1-cAMP-Efg1 signalling cascade is inhibited by farnesol, a C. albicans autoregulatory factor, and small molecules such as dodecanol. In cultures containing farnesol or dodecanol, hypha formation was restored upon addition of dibutyryl-cAMP. The CAI4-Ras1(G13V) strain, which carries a dominant-active variant of Ras1 and forms hyphae in the absence of inducing stimuli, grew as yeast in medium with farnesol or dodecanol; the heat shock sensitivity of the CAI4-Ras1(G13V) strain was also suppressed by these compounds. Neither Pde1 nor Pde2 was necessary for the repression of hyphal growth by farnesol or dodecanol. Two transcripts, CTA1 and HSP12, which are at higher levels upon mutation of Ras1 or Cdc35, were increased in abundance in cells grown with farnesol or dodecanol. Microscopic analysis of strains carrying CTA1 and HWP1 promoter fusions grown with intermediate concentrations of farnesol or dodecanol indicated a link between cells with the increased expression of cAMP-repressed genes and cells repressed for hypha formation. Because several cAMP-controlled outputs are affected by farnesol and dodecanol, our findings suggest that these compounds impact activity of the Ras1-Cdc35 pathway, thus leading to an alteration of C. albicans morphology.
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Affiliation(s)
- Amber Davis-Hanna
- Department of Microbiology and Immunology, Dartmouth Medical School, Hanover, NH 03755, USA
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Nuclear translocation of Gln3 in response to nutrient signals requires Golgi-to-endosome trafficking in Saccharomyces cerevisiae. Proc Natl Acad Sci U S A 2008; 105:7194-9. [PMID: 18443284 DOI: 10.1073/pnas.0801087105] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The yeast Saccharomyces cerevisiae has developed specialized mechanisms that enable growth on suboptimal nitrogen sources. Exposure of yeast cells to poor nitrogen sources or treatment with the Tor kinase inhibitor rapamycin elicits activation of Gln3 and transcription of nitrogen catabolite-repressed (NCR) genes whose products function in scavenging and metabolizing nitrogen. Here, we show that mutations in class C and D Vps components, which mediate Golgi-to-endosome vesicle transport, impair nuclear translocation of Gln3, NCR gene activation, and growth in poor nitrogen sources. In nutrient-replete conditions, a significant fraction of Gln3 is peripherally associated with light membranes and partially colocalizes with Vps10-containing foci. These results reveal a role for Golgi-to-endosome vesicular trafficking in TORC1-controlled nuclear translocation of Gln3 and support a model in which Tor-mediated signaling in response to nutrient cues occurs in these compartments. These findings have important implications for nutrient sensing and growth control via mTor pathways in metazoans.
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40
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Galmiche A, Fueller J, Santel A, Krohne G, Wittig I, Doye A, Rolando M, Flatau G, Lemichez E, Rapp UR. Isoform-specific interaction of C-RAF with mitochondria. J Biol Chem 2008; 283:14857-66. [PMID: 18356164 DOI: 10.1074/jbc.m709098200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The proteins of the RAF family (A-RAF, B-RAF, and C-RAF) are serine/threonine kinases that play important roles in development, mature cell regulation, and cancer. Although it is widely held that their localization on membranes is an important aspect of their function, there are few data that address this aspect of their mode of action. Here, we report that each member of the RAF family exhibits a specific distribution at the level of cellular membranes and that C-RAF is the only isoform that directly targets mitochondria. We found that the RAF kinases exhibit intrinsic differences in terms of mitochondrial affinity and that C-RAF is the only isoform that binds this organelle efficiently. This affinity is conferred by the C-RAF amino-terminal domain and does not depend on the presence of RAS GTPases on the surface of mitochondria. Finally, we analyzed the consequences of C-RAF activation on mitochondria and observed that this event dramatically changes their morphology and their subcellular distribution. Our observations indicate that: (i) RAF kinases exhibit different localizations at the level of cellular membranes; (ii) C-RAF is the only isoform that directly binds mitochondria; and (iii) through its functional coupling with MEK, C-RAF regulates the shape and the cellular distribution of mitochondria.
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Affiliation(s)
- Antoine Galmiche
- Institut für Medizinische Strahlenkunde und Zellforschung, University of Würzburg, Würzburg, Germany.
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Omerovic J, Laude AJ, Prior IA. Ras proteins: paradigms for compartmentalised and isoform-specific signalling. Cell Mol Life Sci 2007; 64:2575-89. [PMID: 17628742 PMCID: PMC2561238 DOI: 10.1007/s00018-007-7133-8] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Ras GTPases mediate a wide variety of cellular processes by converting a multitude of extracellular stimuli into specific biological responses including proliferation, differentiation and survival. In mammalian cells, three ras genes encode four Ras isoforms (H-Ras, K-Ras4A, K-Ras4B and N-Ras) that are highly homologous but functionally distinct. Differences between the isoforms, including their post-translational modifications and intracellular sorting, mean that Ras has emerged as an important model system of compartmentalised signalling and membrane biology. Ras isoforms in different subcellular locations are proposed to recruit distinct upstream and downstream accessory proteins and activate multiple signalling pathways. Here, we summarise data relating to isoform-specific signalling, its role in disease and the mechanisms promoting compartmentalised signalling. Further understanding of this field will reveal the role of Ras signalling in development, cellular homeostasis and cancer and may suggest new therapeutic approaches.
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Affiliation(s)
- J. Omerovic
- Physiological Laboratory, University of Liverpool, Crown St., Liverpool, L69 3BX UK
| | - A. J. Laude
- Physiological Laboratory, University of Liverpool, Crown St., Liverpool, L69 3BX UK
| | - I. A. Prior
- Physiological Laboratory, University of Liverpool, Crown St., Liverpool, L69 3BX UK
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Galmiche A, Fueller J. RAF kinases and mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2007; 1773:1256-62. [PMID: 17442414 DOI: 10.1016/j.bbamcr.2006.10.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2006] [Revised: 10/19/2006] [Accepted: 10/20/2006] [Indexed: 01/29/2023]
Abstract
Over the past decade, several investigators reported that a fraction of the RAF kinases are recruited to the mitochondria. Although we are still far from a global understanding of the molecular consequences of RAF translocation on mitochondrial physiology and metabolism, the recent description of some molecular interactions that are established by C-RAF in this organelle, principally with the proteins Bcl-2 and Bag-1, provides some clues. Here, we discuss the possible contribution of RAF targeting to mitochondria to their modulation of apoptosis signaling, as well as to this organelle's physiology. In addition, we discuss the possible modulation of the mitochondrial metabolism by RAF oncogenes in the context of cancer.
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Affiliation(s)
- Antoine Galmiche
- Institut für Medizinische Strahlenkunde und Zellforschung (MSZ), University of Würzburg, D-97078 Würzburg, Germany.
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Abstract
Palmitate modifies both peripheral and integral membrane proteins and its addition can be permanent or transient, which makes it unique among the lipid modifications of proteins. The presence of palmitate on a protein affects how the protein interacts with lipids and proteins in a membrane compartment, and the reversibility of palmitoylation allows different modes of trafficking between membrane compartments. Here, we review recent studies that have provided insights into the mechanisms that mediate the functional consequences of this versatile modification.
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Affiliation(s)
- Maurine E Linder
- Department of Cell Biology and Physiology, Washington University School of Medicine, Box 8228, 660 South Euclid Avenue, St. Louis, Missouri 63110, USA.
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44
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Current awareness on yeast. Yeast 2006. [DOI: 10.1002/yea.1319] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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