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Bischof L, Schweitzer F, Schmitz HP, Heinisch JJ. The small yeast GTPase Rho5 requires specific mitochondrial outer membrane proteins for translocation under oxidative stress and interacts with the VDAC Por1. Eur J Cell Biol 2024; 103:151405. [PMID: 38503132 DOI: 10.1016/j.ejcb.2024.151405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Revised: 02/29/2024] [Accepted: 03/14/2024] [Indexed: 03/21/2024] Open
Abstract
Yeast Rho5 is a small GTPase which mediates the response to nutrient and oxidative stress, and triggers mitophagy and apoptosis. We here studied the rapid translocation of a GFP-tagged Rho5 to mitochondria under such stress conditions by live-cell fluorescence microscopy in the background of strains lacking different mitochondrial outer membrane proteins (MOMP). Fun14, Msp1 and Alo1 were found to be required for efficient recruitment of the GTPase, whereas translocation of Dck1 and Lmo1, the subunits of its dimeric GDP/GTP exchange factor (GEF), remained unaffected. An influence of the voltage-dependent anion channel (VDAC) Por1 on the association of GFP-Rho5 with mitochondria under oxidative stress conditions appeared to be strain-dependent. However, epistasis analyses and bimolecular fluorescence complementation (BiFC) studies indicate a genetic and physical interaction. All four strains lacking a single MOMP were investigated for their effect on mitophagy.
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Affiliation(s)
- Linnet Bischof
- Universität Osnabrück, Fachbereich Biologie/Chemie, AG Genetik, Barbarastr. 11, Osnabrück D-49076, Germany
| | - Franziska Schweitzer
- Universität Osnabrück, Fachbereich Biologie/Chemie, AG Genetik, Barbarastr. 11, Osnabrück D-49076, Germany
| | - Hans-Peter Schmitz
- Universität Osnabrück, Fachbereich Biologie/Chemie, AG Genetik, Barbarastr. 11, Osnabrück D-49076, Germany
| | - Jürgen J Heinisch
- Universität Osnabrück, Fachbereich Biologie/Chemie, AG Genetik, Barbarastr. 11, Osnabrück D-49076, Germany.
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Bailly C, Degand C, Laine W, Sauzeau V, Kluza J. Implication of Rac1 GTPase in molecular and cellular mitochondrial functions. Life Sci 2024; 342:122510. [PMID: 38387701 DOI: 10.1016/j.lfs.2024.122510] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Revised: 02/07/2024] [Accepted: 02/16/2024] [Indexed: 02/24/2024]
Abstract
Rac1 is a member of the Rho GTPase family which plays major roles in cell mobility, polarity and migration, as a fundamental regulator of actin cytoskeleton. Signal transduction by Rac1 occurs through interaction with multiple effector proteins, and its activity is regulated by guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs). The small protein is mainly anchored to the inner side of the plasma membrane but it can be found in endocellular compartments, notably endosomes and cell nuclei. The protein localizes also into mitochondria where it contributes to the regulation of mitochondrial dynamics, including both mitobiogenesis and mitophagy, in addition to signaling processes via different protein partners, such as the proapoptotic protein Bcl-2 and chaperone sigma-1 receptor (σ-1R). The mitochondrial form of Rac1 (mtRac1) has been understudied thus far, but it is as essential as the nuclear or plasma membrane forms, via its implication in regulation of oxidative stress and DNA damages. Rac1 is subject to diverse post-translational modifications, notably to a geranylgeranylation which contributes importantly to its mitochondrial import and its anchorage to mitochondrial membranes. In addition, Rac1 contributes to the mitochondrial translocation of other proteins, such as p53. The mitochondrial localization and functions of Rac1 are discussed here, notably in the context of human diseases such as cancers. Inhibitors of Rac1 have been identified (NSC-23766, EHT-1864) and some are being developed for the treatment of cancer (MBQ-167) or central nervous system diseases (JK-50561). Their effects on mtRac1 warrant further investigations. An overview of mtRac1 is provided here.
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Affiliation(s)
- Christian Bailly
- University of Lille, CNRS, Inserm, CHU Lille, UMR9020 - UMR1277 - Canther - Cancer Heterogeneity, Plasticity and Resistance to Therapies, 59000 Lille, France; University of Lille, Faculty of Pharmacy, Institut de Chimie Pharmaceutique Albert Lespagnol (ICPAL), 3 rue du Professeur Laguesse, 59000 Lille, France; OncoWitan, Consulting Scientific Office, Lille (Wasquehal) 59290, France.
| | - Claire Degand
- University of Lille, CNRS, Inserm, CHU Lille, UMR9020 - UMR1277 - Canther - Cancer Heterogeneity, Plasticity and Resistance to Therapies, 59000 Lille, France
| | - William Laine
- University of Lille, CNRS, Inserm, CHU Lille, UMR9020 - UMR1277 - Canther - Cancer Heterogeneity, Plasticity and Resistance to Therapies, 59000 Lille, France
| | - Vincent Sauzeau
- Université de Nantes, CHU Nantes, CNRS, INSERM, Institut du thorax, Nantes, France
| | - Jérôme Kluza
- University of Lille, CNRS, Inserm, CHU Lille, UMR9020 - UMR1277 - Canther - Cancer Heterogeneity, Plasticity and Resistance to Therapies, 59000 Lille, France
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3
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Bischof L, Schweitzer F, Heinisch JJ. Functional Conservation of the Small GTPase Rho5/Rac1-A Tale of Yeast and Men. Cells 2024; 13:472. [PMID: 38534316 DOI: 10.3390/cells13060472] [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: 02/17/2024] [Revised: 03/02/2024] [Accepted: 03/06/2024] [Indexed: 03/28/2024] Open
Abstract
Small GTPases are molecular switches that participate in many essential cellular processes. Amongst them, human Rac1 was first described for its role in regulating actin cytoskeleton dynamics and cell migration, with a close relation to carcinogenesis. More recently, the role of Rac1 in regulating the production of reactive oxygen species (ROS), both as a subunit of NADPH oxidase complexes and through its association with mitochondrial functions, has drawn attention. Malfunctions in this context affect cellular plasticity and apoptosis, related to neurodegenerative diseases and diabetes. Some of these features of Rac1 are conserved in its yeast homologue Rho5. Here, we review the structural and functional similarities and differences between these two evolutionary distant proteins and propose yeast as a useful model and a device for high-throughput screens for specific drugs.
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Affiliation(s)
- Linnet Bischof
- AG Genetik, Fachbereich Biologie/Chemie, University of Osnabrück, Barbarastrasse 11, D-49076 Osnabrück, Germany
| | - Franziska Schweitzer
- AG Genetik, Fachbereich Biologie/Chemie, University of Osnabrück, Barbarastrasse 11, D-49076 Osnabrück, Germany
| | - Jürgen J Heinisch
- AG Genetik, Fachbereich Biologie/Chemie, University of Osnabrück, Barbarastrasse 11, D-49076 Osnabrück, Germany
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4
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Chen L, Champramary S, Sahu N, Indic B, Szűcs A, Nagy G, Maróti G, Pap B, Languar O, Vágvölgyi C, Nagy LG, Kredics L, Sipos G. Dual RNA-Seq Profiling Unveils Mycoparasitic Activities of Trichoderma atroviride against Haploid Armillaria ostoyae in Antagonistic Interaction Assays. Microbiol Spectr 2023; 11:e0462622. [PMID: 37140425 PMCID: PMC10269595 DOI: 10.1128/spectrum.04626-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2022] [Accepted: 04/11/2023] [Indexed: 05/05/2023] Open
Abstract
Armillaria ostoyae, a species among the destructive forest pathogens from the genus Armillaria, causes root rot disease on woody plants worldwide. Efficient control measures to limit the growth and impact of this severe underground pathogen are under investigation. In a previous study, a new soilborne fungal isolate, Trichoderma atroviride SZMC 24276 (TA), exhibited high antagonistic efficacy, which suggested that it could be utilized as a biocontrol agent. The dual culture assay results indicated that the haploid A. ostoyae-derivative SZMC 23085 (AO) (C18/9) is highly susceptible to the mycelial invasion of TA. In the present study, we analyzed the transcriptome of AO and that of TA in in vitro dual culture assays to test the molecular arsenal of Trichoderma antagonism and the defense mechanisms of Armillaria. We conducted time-course analysis and functional annotation and analyzed enriched pathways and differentially expressed genes including biocontrol-related candidate genes from TA and defense-related candidate genes from AO. The results indicated that TA deployed several biocontrol mechanisms when confronted with AO. In response, AO initiated multiple defense mechanisms to protect against the fungal attack. To our knowledge, the present study offers the first transcriptome analysis of a biocontrol fungus attacking AO. Overall, this study provides insights that aid the further exploration of plant pathogen-biocontrol agent interaction mechanisms. IMPORTANCE Armillaria species can survive for decades in the soil on dead woody debris, develop rapidly under favorable conditions, and harmfully infect newly planted forests. Our previous study found Trichoderma atroviride to be highly effective in controlling Armillaria growth; therefore, our current work explored the molecular mechanisms that might play a key role in Trichoderma-Armillaria interactions. Direct confrontation assays combined with time course-based dual transcriptome analysis provided a reliable system for uncovering the interactive molecular dynamics between the fungal plant pathogen and its mycoparasitic partner. Furthermore, using a haploid Armillaria isolate allowed us to survey the deadly prey-invading activities of the mycoparasite and the ultimate defensive strategies of its prey. Our current study provides detailed insights into the essential genes and mechanisms involved in Armillaria defense against Trichoderma and the genes potentially involved in the efficiency of Trichoderma to control Armillaria. In addition, using a sensitive haploid Armillaria strain (C18/9), with its complete genome data already available, also offers the opportunity to test possible variable molecular responses of Armillaria ostoyae toward diverse Trichoderma isolates with various biocontrol abilities. Initial molecular tests of the dual interactions may soon help to develop a targeted biocontrol intervention with mycoparasites against plant pathogens.
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Affiliation(s)
- Liqiong Chen
- Department of Microbiology, Faculty of Science and Informatics, University of Szeged, Szeged, Hungary
| | - Simang Champramary
- Department of Microbiology, Faculty of Science and Informatics, University of Szeged, Szeged, Hungary
- Functional Genomics and Bioinformatics Group, Institute of Forest and Natural Resource Management, Faculty of Forestry, University of Sopron, Sopron, Hungary
| | - Neha Sahu
- Synthetic and Systems Biology Unit, Biological Research Center, Szeged, Hungary
| | - Boris Indic
- Functional Genomics and Bioinformatics Group, Institute of Forest and Natural Resource Management, Faculty of Forestry, University of Sopron, Sopron, Hungary
| | - Attila Szűcs
- Department of Microbiology, Faculty of Science and Informatics, University of Szeged, Szeged, Hungary
| | - Gábor Nagy
- Department of Microbiology, Faculty of Science and Informatics, University of Szeged, Szeged, Hungary
| | | | - Bernadett Pap
- Institute of Plant Biology, Biological Research Center, Szeged, Hungary
| | - Omar Languar
- Department of Microbiology, Faculty of Science and Informatics, University of Szeged, Szeged, Hungary
- Functional Genomics and Bioinformatics Group, Institute of Forest and Natural Resource Management, Faculty of Forestry, University of Sopron, Sopron, Hungary
| | - Csaba Vágvölgyi
- Department of Microbiology, Faculty of Science and Informatics, University of Szeged, Szeged, Hungary
| | - László G. Nagy
- Synthetic and Systems Biology Unit, Biological Research Center, Szeged, Hungary
| | - László Kredics
- Department of Microbiology, Faculty of Science and Informatics, University of Szeged, Szeged, Hungary
| | - György Sipos
- Functional Genomics and Bioinformatics Group, Institute of Forest and Natural Resource Management, Faculty of Forestry, University of Sopron, Sopron, Hungary
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The Intracellular Distribution of the Small GTPase Rho5 and Its Dimeric Guanidine Nucleotide Exchange Factor Dck1/Lmo1 Determine Their Function in Oxidative Stress Response. Int J Mol Sci 2022; 23:ijms23147896. [PMID: 35887245 PMCID: PMC9317549 DOI: 10.3390/ijms23147896] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Revised: 07/14/2022] [Accepted: 07/16/2022] [Indexed: 11/16/2022] Open
Abstract
Rho5, the yeast homolog of human Rac1, is a small GTPase which regulates the cell response to nutrient and oxidative stress by inducing mitophagy and apoptosis. It is activated by a dimeric GEF composed of the subunits Dck1 and Lmo1. Upon stress, all three proteins rapidly translocate from the cell surface (Rho5) and a diffuse cytosolic distribution (Dck1 and Lmo1) to mitochondria, with translocation of the GTPase depending on both GEF subunits. We here show that the latter associate with mitochondria independent from each other and from Rho5. The trapping of Dck1-GFP or GFP-Lmo1 to the mitochondrial surface by a specific nanobody fused to the transmembrane domain (TMD) of Fis1 results in a loss of function, mimicking the phenotypes of the respective gene deletions, dck1 or lmo1. Direct fusion of Rho5 to Fis1TMD, i.e., permanent attachment to the mitochondria, also mimics the phenotypes of an rho5 deletion. Together, these data suggest that the GTPase needs to be activated at the plasma membrane prior to its translocation in order to fulfill its function in the oxidative stress response. This notion is substantiated by the observation that strains carrying fusions of Rho5 to the cell wall integrity sensor Mid2, confining the GTPase to the plasma membrane, retained their function. We propose a model in which Rho5 activated at the plasma membrane represses the oxidative stress response under standard growth conditions. This repression is relieved upon its GEF-mediated translocation to mitochondria, thus triggering mitophagy and apoptosis.
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Yi W, Zhu R, Hou X, Wu F, Feng R. Integrated Analysis Reveals S100a8/a9 Regulates Autophagy and Apoptosis through the MAPK and PI3K-AKT Signaling Pathway in the Early Stage of Myocardial Infarction. Cells 2022; 11:cells11121911. [PMID: 35741040 PMCID: PMC9221389 DOI: 10.3390/cells11121911] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Revised: 06/07/2022] [Accepted: 06/09/2022] [Indexed: 11/16/2022] Open
Abstract
Myocardial infarction (MI), a type of coronary heart disease, has had a significantly increased incidence in recent years. The balance of cardiomyocyte apoptosis and autophagy after MI is one of the main determinants of patient prognosis. Both affect myocardial fibrosis and ventricular remodeling and regulate cell survival. However, there are few studies on the regulation mechanism of cardiomyocyte autophagy and apoptosis in the early stage after MI. In this study, based on analyzing the scRNA-seq and mRNA-seq data of mice in the early stage of MI, we found that the expression of S100a8 and S100a9 increased first and then decreased in the early stage of MI, and their expression level changed with the number of neutrophils. Further, through the functional enrichment analysis of the differentially expressed genes, we found that S100a8 and S100a9 were simultaneously associated with autophagy and apoptosis and could regulate autophagy and apoptosis of cardiomyocytes through MAPK or PI3K-AKT signaling pathways. This study provides valuable insights for clarifying the pathogenesis of early stage MI and improving its early treatment.
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Affiliation(s)
| | | | | | | | - Rui Feng
- Correspondence: ; Tel.: +86-13386840836; Fax: +86-024-31939448
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7
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Musielak M, Sterk CC, Schubert F, Meyer C, Paululat A, Heinisch JJ. The small GTPase KlRho5 responds to oxidative stress and affects cytokinesis. J Cell Sci 2021; 134:271953. [PMID: 34435638 DOI: 10.1242/jcs.258301] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Accepted: 08/19/2021] [Indexed: 01/11/2023] Open
Abstract
Rho5 is the yeast homolog of the human small GTPase Rac1. We characterized the genes encoding Rho5 and the subunits of its dimeric activating guanine-nucleotide-exchange factor (GEF), Dck1 and Lmo1, in the yeast Kluyveromyces lactis. Rapid translocation of the three GFP-tagged components to mitochondria upon oxidative stress and carbon starvation indicate a similar function of KlRho5 in energy metabolism and mitochondrial dynamics as described for its Saccharomyces cerevisiae homolog. Accordingly, Klrho5 deletion mutants are hyper-resistant towards hydrogen peroxide. Moreover, synthetic lethalities of rho5 deletions with key components in nutrient sensing, such as sch9 and gpr1, are not conserved in K. lactis. Instead, Klrho5 deletion mutants display morphological defects with strengthened lateral cell walls and protruding bud scars. The latter result from aberrant cytokinesis, as observed by following the budding process in vivo and by transmission electron microscopy of the bud neck region. This phenotype can be suppressed by KlCDC42G12V, which encodes a hyper-active variant. Data from live-cell fluorescence microscopy support the notion that KlRho5 interferes with the actin moiety of the contractile actomyosin ring, with consequences different from those previously reported for mutants lacking myosin.
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Affiliation(s)
- Marius Musielak
- Universität Osnabrück, Fachbereich Biologie/Chemie, AG Genetik, Barbarastr. 11, D-49076 Osnabrück, Germany
| | - Carolin C Sterk
- Universität Osnabrück, Fachbereich Biologie/Chemie, AG Genetik, Barbarastr. 11, D-49076 Osnabrück, Germany
| | - Felix Schubert
- Universität Osnabrück, Fachbereich Biologie/Chemie, AG Genetik, Barbarastr. 11, D-49076 Osnabrück, Germany
| | - Christian Meyer
- Universität Osnabrück, Fachbereich Biologie/Chemie, AG Zoologie, Barbarastr. 11, D-49076 Osnabrück, Germany
| | - Achim Paululat
- Universität Osnabrück, Fachbereich Biologie/Chemie, AG Zoologie, Barbarastr. 11, D-49076 Osnabrück, Germany
| | - Jürgen J Heinisch
- Universität Osnabrück, Fachbereich Biologie/Chemie, AG Genetik, Barbarastr. 11, D-49076 Osnabrück, Germany
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8
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Huang S, Deng W, Wang P, Yan Y, Xie C, Cao X, Chen M, Zhang C, Shi D, Dong Y, Cheng P, Xu H, Zhu W, Hu Z, Tang B, Zhu J. Fermitin family member 2 promotes melanoma progression by enhancing the binding of p-α-Pix to Rac1 to activate the MAPK pathway. Oncogene 2021; 40:5626-5638. [PMID: 34321603 PMCID: PMC8445820 DOI: 10.1038/s41388-021-01954-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 06/06/2021] [Accepted: 07/09/2021] [Indexed: 01/02/2023]
Abstract
We identified fermitin family member 2 (FERMT2, also known as kindlin-2) as a potential target in A375 cell line by siRNA library screening. Drugs that target mutant BRAF kinase lack durable efficacy in the treatment of melanoma because of acquired resistance, thus the identification of novel therapeutic targets is needed. Immunohistochemistry was used to identify kindlin-2 expression in melanoma samples. The interaction between kindlin-2 and Rac1 or p-Rac/Cdc42 guanine nucleotide exchange factor 6 (α-Pix) was investigated. Finally, the tumor suppressive role of kindlin-2 was validated in vitro and in vivo. Analysis of clinical samples and Oncomine data showed that higher levels of kindlin-2 predicted a more advanced T stage and M stage and facilitated metastasis and recurrence. Kindlin-2 knockdown significantly inhibited melanoma growth and migration, whereas kindlin-2 overexpression had the inverse effects. Further study showed that kindlin-2 could specifically bind to p-α-Pix(S13) and Rac1 to induce a switch from the inactive Rac1-GDP conformation to the active Rac1-GTP conformation and then stimulate the downstream MAPK pathway. Moreover, we revealed that a Rac1 inhibitor suppressed melanoma growth and metastasis and the combination of the Rac1 inhibitor and vemurafenib resulted in a better therapeutic outcome than monotherapy in melanoma with high kindlin-2 expression and BRAF mutation. Our results demonstrated that kindlin-2 promoted melanoma progression, which was attributed to specific binding to p-α-Pix(S13) and Rac1 to stimulate the downstream MAPK pathway. Thus, kindlin-2 could be a potential therapeutic target for treating melanoma.
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Affiliation(s)
- Shaobin Huang
- The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, China
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center of Cancer Medicine, Guangzhou, China
- The Sixth Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Wuguo Deng
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center of Cancer Medicine, Guangzhou, China
| | - Peng Wang
- The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, China
| | - Yue Yan
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center of Cancer Medicine, Guangzhou, China
| | - Chuanbo Xie
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center of Cancer Medicine, Guangzhou, China
| | - Xiaoling Cao
- The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, China
| | - Miao Chen
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center of Cancer Medicine, Guangzhou, China
| | - Changlin Zhang
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center of Cancer Medicine, Guangzhou, China
| | - Dingbo Shi
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center of Cancer Medicine, Guangzhou, China
| | - Yunxian Dong
- The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, China
| | - Pu Cheng
- The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, China
| | - Hailin Xu
- The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, China
| | - Wenkai Zhu
- Department of Chemistry, Portland State University, Portland, OR, USA
| | - Zhicheng Hu
- The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, China.
| | - Bing Tang
- The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, China.
| | - Jiayuan Zhu
- The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, China.
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9
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Sterk C, Gräber L, Schmitz HP, Heinisch JJ. Analysis of Functional Domains in Rho5, the Yeast Homolog of Human Rac1 GTPase, in Oxidative Stress Response. Int J Mol Sci 2019; 20:ijms20225550. [PMID: 31703278 PMCID: PMC6888954 DOI: 10.3390/ijms20225550] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 11/03/2019] [Accepted: 11/05/2019] [Indexed: 12/23/2022] Open
Abstract
The small GTPase Rho5 of Saccharomyces cerevisiae is required for proper regulation of different signaling pathways, which includes the response to cell wall, osmotic, nutrient, and oxidative stress. We here show that proper in vivo function and intracellular distribution of Rho5 depends on its hypervariable region at the carboxyterminal end, which includes the CAAX box for lipid modification, a preceding polybasic region (PBR) carrying a serine residue, and a 98 amino acid–specific insertion only present in Rho5 of S. cerevisiae but not in its human homolog Rac1. Results from trapping GFP-Rho5 variants to the mitochondrial surface suggest that the GTPase needs to be activated at the plasma membrane prior to its translocation to mitochondria in order to fulfil its role in oxidative stress response. These findings are supported by heterologous expression of a codon-optimized human RAC1 gene, which can only complement a yeast rho5 deletion in a chimeric fusion with RHO5 sequences that restore the correct spatiotemporal distribution of the encoded protein.
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