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Huber RJ, Kim WD. Trafficking of adhesion and aggregation-modulating proteins during the early stages of Dictyostelium development. Cell Signal 2024; 121:111292. [PMID: 38986731 DOI: 10.1016/j.cellsig.2024.111292] [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: 07/03/2024] [Accepted: 07/06/2024] [Indexed: 07/12/2024]
Abstract
The social amoeba Dictyostelium discoideum has been studied for close to a century to better understand conserved cellular and developmental processes. The life cycle of this model eukaryote is composed of a unicellular growth phase and a multicellular developmental phase that is induced by starvation. When starved, individual cells undergo chemotactic aggregation to form multicellular mounds that develop into slugs. Terminal differentiation of cells within slugs forms fruiting bodies, each composed of a stalk that supports a mass of viable spores that germinate and restart the life cycle when nutrients become available. Calcium-dependent cell adhesion protein A (CadA) and countin (CtnA) are two proteins that regulate adhesion and aggregation, respectively, during the early stages of D. discoideum development. While the functions of these proteins have been well-studied, the mechanisms regulating their trafficking are not fully understood. In this study, we reveal pathways and cellular components that regulate the intracellular and extracellular amounts of CadA and CtnA during aggregation. During growth and starvation, CtnA localizes to cytoplasmic vesicles and punctae. We show that CtnA is glycosylated and this post-translational modification is required for its secretion. Upon autophagy induction, a signal peptide for secretion facilitates the release of CtnA from cells via a pathway involving the μ subunit of the AP3 complex (Apm3) and the WASP and SCAR homolog, WshA. Additionally, CtnA secretion is negatively regulated by the D. discoideum orthologs of the human non-selective cation channel mucolipin-1 (Mcln) and sorting receptor sortilin (Sort1). As for CadA, it localizes to the cell periphery in growth-phase and starved cells. The intracellular and extracellular amounts of CadA are modulated by autophagy genes (atg1, atg9), Apm3, WshA, and Mcln. We integrate these data with previously published findings to generate a comprehensive model summarizing the trafficking of CadA and CtnA in D. discoideum. Overall, this study enhances our understanding of protein trafficking during D. discoideum aggregation, and more broadly, provides insight into the multiple pathways that regulate protein trafficking and secretion in all eukaryotes.
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Affiliation(s)
- Robert J Huber
- Department of Biology, Trent University, Peterborough, Ontario, Canada.
| | - William D Kim
- Environmental and Life Sciences Graduate Program, Trent University, Peterborough, Ontario, Canada
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Wu J, Sheng Y, Mai S, Zhong Y, Dai S, Luo Y, Sheng X. The function of the ATG8 in the cilia and cortical microtubule maintenance of Euplotes amieti. PROTOPLASMA 2024:10.1007/s00709-024-01957-8. [PMID: 38769089 DOI: 10.1007/s00709-024-01957-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2023] [Accepted: 05/03/2024] [Indexed: 05/22/2024]
Abstract
Autophagy regulates the formation of primary cilia, which in turn affects autophagy. The relationship between autophagy and cilia is known to be bidirectional although the specific mechanisms involved have yet to be elucidated. In this study, we found for the first time that ATG8 protein localizes in the basal body of the dorsal kineties and the base of the ventral cirri in Euplotes amieti. ATG8 protein maintains the structural integrity of cilia and plays a role in the construction of the cortical ciliature and microtubule cytoskeleton associated with cilia. ATG8 gene interference leads to the degradation of IFT88, the transport protein in cilia, thus inhibiting the generation of cilia, and affecting the swing of cilia. This influences the swimming speed and cilia pattern, leading to death in Euplotes amieti.
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Affiliation(s)
- Junlin Wu
- Department of Biochemistry, Zunyi Medical University, Zunyi, 563000, People's Republic of China
| | - Yan Sheng
- Laboratory of Basic Medical Morphology, Zunyi Medical University, Zunyi, 563000, People's Republic of China
| | - Shihuan Mai
- School of Medical Imaging, Zunyi Medical University, Zunyi, 563000, People's Republic of China
| | - Yanhao Zhong
- School of Medical Imaging, Zunyi Medical University, Zunyi, 563000, People's Republic of China
| | - Shengrong Dai
- School of Medical Imaging, Zunyi Medical University, Zunyi, 563000, People's Republic of China
| | - Yupeng Luo
- School of Medical Imaging, Zunyi Medical University, Zunyi, 563000, People's Republic of China
| | - Xin Sheng
- Department of Biochemistry, Zunyi Medical University, Zunyi, 563000, People's Republic of China.
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3
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Huber RJ, Kim WD, Wilson-Smillie MLDM. Mechanisms regulating the intracellular trafficking and release of CLN5 and CTSD. Traffic 2024; 25:e12925. [PMID: 38272448 DOI: 10.1111/tra.12925] [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: 08/01/2023] [Revised: 11/20/2023] [Accepted: 11/21/2023] [Indexed: 01/27/2024]
Abstract
Ceroid lipofuscinosis neuronal 5 (CLN5) and cathepsin D (CTSD) are soluble lysosomal enzymes that also localize extracellularly. In humans, homozygous mutations in CLN5 and CTSD cause CLN5 disease and CLN10 disease, respectively, which are two subtypes of neuronal ceroid lipofuscinosis (commonly known as Batten disease). The mechanisms regulating the intracellular trafficking of CLN5 and CTSD and their release from cells are not well understood. Here, we used the social amoeba Dictyostelium discoideum as a model system to examine the pathways and cellular components that regulate the intracellular trafficking and release of the D. discoideum homologs of human CLN5 (Cln5) and CTSD (CtsD). We show that both Cln5 and CtsD contain signal peptides for secretion that facilitate their release from cells. Like Cln5, extracellular CtsD is glycosylated. In addition, Cln5 release is regulated by the amount of extracellular CtsD. Autophagy induction promotes the release of Cln5, and to a lesser extent CtsD. Release of Cln5 requires the autophagy proteins Atg1, Atg5, and Atg9, as well as autophagosomal-lysosomal fusion. Atg1 and Atg5 are required for the release of CtsD. Together, these data support a model where Cln5 and CtsD are actively released from cells via their signal peptides for secretion and pathways linked to autophagy. The release of Cln5 and CtsD from cells also requires microfilaments and the D. discoideum homologs of human AP-3 complex mu subunit, the lysosomal-trafficking regulator LYST, mucopilin-1, and the Wiskott-Aldrich syndrome-associated protein WASH, which all regulate lysosomal exocytosis in this model organism. These findings suggest that lysosomal exocytosis also facilitates the release of Cln5 and CtsD from cells. In addition, we report the roles of ABC transporters, microtubules, osmotic stress, and the putative D. discoideum homologs of human sortilin and cation-independent mannose-6-phosphate receptor in regulating the intracellular/extracellular distribution of Cln5 and CtsD. In total, this study identifies the cellular mechanisms regulating the release of Cln5 and CtsD from D. discoideum cells and provides insight into how altered trafficking of CLN5 and CTSD causes disease in humans.
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Affiliation(s)
- Robert J Huber
- Department of Biology, Trent University, Peterborough, Ontario, Canada
- Environmental and Life Sciences Graduate Program, Trent University, Peterborough, Ontario, Canada
| | - William D Kim
- Environmental and Life Sciences Graduate Program, Trent University, Peterborough, Ontario, Canada
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4
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Rahman RJ, Rijal R, Jing S, Chen TA, Ismail I, Gomer RH. Polyphosphate uses mTOR, pyrophosphate, and Rho GTPase components to potentiate bacterial survival in Dictyostelium. mBio 2023; 14:e0193923. [PMID: 37754562 PMCID: PMC10653871 DOI: 10.1128/mbio.01939-23] [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: 07/25/2023] [Accepted: 07/31/2023] [Indexed: 09/28/2023] Open
Abstract
IMPORTANCE Although most bacteria are quickly killed after phagocytosis by a eukaryotic cell, some pathogenic bacteria escape death after phagocytosis. Pathogenic Mycobacterium species secrete polyP, and the polyP is necessary for the bacteria to prevent their killing after phagocytosis. Conversely, exogenous polyP prevents the killing of ingested bacteria that are normally killed after phagocytosis by human macrophages and the eukaryotic microbe Dictyostelium discoideum. This suggests the possibility that in these cells, a signal transduction pathway is used to sense polyP and prevent killing of ingested bacteria. In this report, we identify key components of the polyP signal transduction pathway in D. discoideum. In cells lacking these components, polyP is unable to inhibit killing of ingested bacteria. The pathway components have orthologs in human cells, and an exciting possibility is that pharmacologically blocking this pathway in human macrophages would cause them to kill ingested pathogens such as Mycobacterium tuberculosis.
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Affiliation(s)
- Ryan J. Rahman
- Department of Biology, Texas A&M University, College Station, Texas, USA
| | - Ramesh Rijal
- Department of Biology, Texas A&M University, College Station, Texas, USA
| | - Shiyu Jing
- Department of Biology, Texas A&M University, College Station, Texas, USA
| | - Te-An Chen
- Department of Biology, Texas A&M University, College Station, Texas, USA
| | - Issam Ismail
- Department of Biology, Texas A&M University, College Station, Texas, USA
| | - Richard H. Gomer
- Department of Biology, Texas A&M University, College Station, Texas, USA
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Xiong Q, Feng R, Fischer S, Karow M, Stumpf M, Meßling S, Nitz L, Müller S, Clemen CS, Song N, Li P, Wu C, Eichinger L. Proteasomes of Autophagy-Deficient Cells Exhibit Alterations in Regulatory Proteins and a Marked Reduction in Activity. Cells 2023; 12:1514. [PMID: 37296637 PMCID: PMC10252828 DOI: 10.3390/cells12111514] [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: 04/03/2023] [Accepted: 05/26/2023] [Indexed: 06/12/2023] Open
Abstract
Autophagy and the ubiquitin proteasome system are the two major processes for the clearance and recycling of proteins and organelles in eukaryotic cells. Evidence is accumulating that there is extensive crosstalk between the two pathways, but the underlying mechanisms are still unclear. We previously found that autophagy 9 (ATG9) and 16 (ATG16) proteins are crucial for full proteasomal activity in the unicellular amoeba Dictyostelium discoideum. In comparison to AX2 wild-type cells, ATG9-and ATG16- cells displayed a 60%, and ATG9-/16- cells a 90%, decrease in proteasomal activity. Mutant cells also showed a significant increase in poly-ubiquitinated proteins and contained large ubiquitin-positive protein aggregates. Here, we focus on possible reasons for these results. Reanalysis of published tandem mass tag-based quantitative proteomic results of AX2, ATG9-, ATG16-, and ATG9-/16- cells revealed no change in the abundance of proteasomal subunits. To identify possible differences in proteasome-associated proteins, we generated AX2 wild-type and ATG16- cells expressing the 20S proteasomal subunit PSMA4 as GFP-tagged fusion protein, and performed co-immunoprecipitation experiments followed by mass spectrometric analysis. The results revealed no significant differences in the abundance of proteasomes between the two strains. However, we found enrichment as well as depletion of proteasomal regulators and differences in the ubiquitination of associated proteins for ATG16-, as compared to AX2 cells. Recently, proteaphagy has been described as a means to replace non-functional proteasomes. We propose that autophagy-deficient D. discoideum mutants suffer from inefficient proteaphagy, which results in the accumulation of modified, less-active, and also of inactive, proteasomes. As a consequence, these cells exhibit a dramatic decrease in proteasomal activity and deranged protein homeostasis.
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Affiliation(s)
- Qiuhong Xiong
- Shanxi Provincial Key Laboratory of Medical Molecular Cell Biology, Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institutes of Biomedical Sciences, Shanxi University, No. 92 Wucheng Road, Taiyuan 030006, China
| | - Rong Feng
- Shanxi Provincial Key Laboratory of Medical Molecular Cell Biology, Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institutes of Biomedical Sciences, Shanxi University, No. 92 Wucheng Road, Taiyuan 030006, China
| | - Sarah Fischer
- Center for Biochemistry, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Cologne, Germany
| | - Malte Karow
- Center for Biochemistry, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Cologne, Germany
| | - Maria Stumpf
- Center for Biochemistry, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Cologne, Germany
| | - Susanne Meßling
- Center for Biochemistry, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Cologne, Germany
| | - Leonie Nitz
- Center for Biochemistry, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Cologne, Germany
| | - Stefan Müller
- CECAD Proteomics Facility, Center for Molecular Medicine Cologne, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 26, 50931 Cologne, Germany
| | - Christoph S. Clemen
- Institute of Aerospace Medicine, German Aerospace Center (DLR), 51147 Cologne, Germany
- Institute of Vegetative Physiology, Medical Faculty, University of Cologne, 50931 Cologne, Germany
| | - Ning Song
- Shanxi Provincial Key Laboratory of Medical Molecular Cell Biology, Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institutes of Biomedical Sciences, Shanxi University, No. 92 Wucheng Road, Taiyuan 030006, China
| | - Ping Li
- Shanxi Provincial Key Laboratory of Medical Molecular Cell Biology, Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institutes of Biomedical Sciences, Shanxi University, No. 92 Wucheng Road, Taiyuan 030006, China
| | - Changxin Wu
- Shanxi Provincial Key Laboratory of Medical Molecular Cell Biology, Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institutes of Biomedical Sciences, Shanxi University, No. 92 Wucheng Road, Taiyuan 030006, China
| | - Ludwig Eichinger
- Center for Biochemistry, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Cologne, Germany
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Starling GP, Phillips BA, Ganesh S, King JS. Katnip is needed to maintain microtubule function and lysosomal delivery to autophagosomes and phagosomes. Mol Biol Cell 2023; 34:ar12. [PMID: 36598819 PMCID: PMC10011725 DOI: 10.1091/mbc.e22-02-0063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The efficient delivery of lysosomes is essential for many cell functions, such as the degradation of unwanted intracellular components by autophagy and the killing and digestion of extracellular microbes within phagosomes. Using the amoeba Dictyostelium discoideum, we find that cells lacking Katnip (Katanin interacting protein) have a general defect in lysosomal delivery and although they make autophagosomes and phagosomes correctly, cells are then unable to digest them. Katnip is largely unstudied yet highly conserved across evolution. Previously studies found that Katnip mutations in animals cause defects in cilia structure. Here we show that Katnip plays a more general role in maintaining microtubule function. We find that loss of Katnip has no overall effect on microtubule dynamics or organization, but is important for the transport and degradation of endocytic cargos. Strikingly, Katnip mutants become highly sensitive to GFP-tubulin expression, which leads to microtubule tangles, defective anaphase extension, and slow cell growth. Our findings establish a general role for Katnip in regulating microtubule function, beyond the roles previously described in cilia. We speculate this is via a key function in microtubule repair, needed to maintain endosomal trafficking and lysosomal degradation.
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Affiliation(s)
| | - Ben A Phillips
- Department of Biomedical Science, University of Sheffield
| | - Sahana Ganesh
- Department of Biomedical Science, University of Sheffield
| | - Jason S King
- Department of Biomedical Science, University of Sheffield
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7
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Vincent O, Antón-Esteban L, Bueno-Arribas M, Tornero-Écija A, Navas MÁ, Escalante R. The WIPI Gene Family and Neurodegenerative Diseases: Insights From Yeast and Dictyostelium Models. Front Cell Dev Biol 2021; 9:737071. [PMID: 34540850 PMCID: PMC8442847 DOI: 10.3389/fcell.2021.737071] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Accepted: 08/12/2021] [Indexed: 02/01/2023] Open
Abstract
WIPIs are a conserved family of proteins with a characteristic 7-bladed β-propeller structure. They play a prominent role in autophagy, but also in other membrane trafficking processes. Mutations in human WIPI4 cause several neurodegenerative diseases. One of them is BPAN, a rare disease characterized by developmental delay, motor disorders, and seizures. Autophagy dysfunction is thought to play an important role in this disease but the precise pathological consequences of the mutations are not well established. The use of simple models such as the yeast Saccharomyces cerevisiae and the social amoeba Dictyostelium discoideum provides valuable information on the molecular and cellular function of these proteins, but also sheds light on possible pathways that may be relevant in the search for potential therapies. Here, we review the function of WIPIs as well as disease-causing mutations with a special focus on the information provided by these simple models.
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Affiliation(s)
- Olivier Vincent
- Instituto de Investigaciones Biomédicas Alberto Sols CSIC/UAM, Madrid, Spain
| | - Laura Antón-Esteban
- Instituto de Investigaciones Biomédicas Alberto Sols CSIC/UAM, Madrid, Spain
| | | | - Alba Tornero-Écija
- Instituto de Investigaciones Biomédicas Alberto Sols CSIC/UAM, Madrid, Spain
| | - María-Ángeles Navas
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad Complutense de Madrid, Madrid, Spain
| | - Ricardo Escalante
- Instituto de Investigaciones Biomédicas Alberto Sols CSIC/UAM, Madrid, Spain
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8
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Tornero-Écija A, Tábara LC, Bueno-Arribas M, Antón-Esteban L, Navarro-Gómez C, Sánchez I, Vincent O, Escalante R. A Dictyostelium model for BPAN disease reveals a functional relationship between the WDR45/WIPI4 homolog Wdr45l and Vmp1 in the regulation of autophagy-associated PtdIns3P and ER stress. Autophagy 2021; 18:661-677. [PMID: 34328055 PMCID: PMC9037511 DOI: 10.1080/15548627.2021.1953262] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
PROPPINs are conserved PtdIns3P-binding proteins required for autophagosome biogenesis that fold into a characteristic group of seven-bladed beta-propellers. Mutations in WDR45/WIPI4, a human member of this family, lead to BPAN, a rare form of neurodegeneration. We have generated mutants for the two PROPPIN proteins present in the model system Dictyostelium discoideum (Atg18 and Wdr45l) and characterized their function. Lack of Wdr45l greatly impairs autophagy, while Atg18 only causes subtle defects in the maturation of autolysosomes. The strong phenotype of the Wdr45l mutant is strikingly similar to that observed in Dictyostelium cells lacking Vmp1, an ER protein required for omegasome formation. Common phenotypes include impaired growth in axenic medium, lack of aggregation, and local enrichment of PtdIns3P as determined by the use of lipid reporters. In addition, Vmp1 and Wdr45l mutants show a chronically active response to ER stress. For both mutants, this altered PtdIns3P localization can be prevented by the additional mutation of the upstream regulator Atg1, which also leads to recovery of axenic growth and reduction of ER stress. We propose that, in addition to an autophagy defect, local autophagy-associated PtdIns3P accumulation might contribute to the pathogenesis of BPAN by disrupting ER homeostasis. The introduction of BPAN-associated mutations in Dictyostelium Wdr45l reveals the impact of pathogenic residues on the function and localization of the protein.
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Affiliation(s)
- Alba Tornero-Écija
- C.S.I.C./U.A.M., Instituto De Investigaciones Biomédicas Alberto Sols, Madrid, Spain
| | - Luis-Carlos Tábara
- C.S.I.C./U.A.M., Instituto De Investigaciones Biomédicas Alberto Sols, Madrid, Spain
| | - Miranda Bueno-Arribas
- C.S.I.C./U.A.M., Instituto De Investigaciones Biomédicas Alberto Sols, Madrid, Spain
| | - Laura Antón-Esteban
- C.S.I.C./U.A.M., Instituto De Investigaciones Biomédicas Alberto Sols, Madrid, Spain
| | | | - Irene Sánchez
- C.S.I.C./U.A.M., Instituto De Investigaciones Biomédicas Alberto Sols, Madrid, Spain
| | - Olivier Vincent
- C.S.I.C./U.A.M., Instituto De Investigaciones Biomédicas Alberto Sols, Madrid, Spain
| | - Ricardo Escalante
- C.S.I.C./U.A.M., Instituto De Investigaciones Biomédicas Alberto Sols, Madrid, Spain
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McLaren MD, Mathavarajah S, Kim WD, Yap SQ, Huber RJ. Aberrant Autophagy Impacts Growth and Multicellular Development in a Dictyostelium Knockout Model of CLN5 Disease. Front Cell Dev Biol 2021; 9:657406. [PMID: 34291044 PMCID: PMC8287835 DOI: 10.3389/fcell.2021.657406] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Accepted: 05/28/2021] [Indexed: 12/22/2022] Open
Abstract
Mutations in CLN5 cause a subtype of neuronal ceroid lipofuscinosis (NCL) called CLN5 disease. While the precise role of CLN5 in NCL pathogenesis is not known, recent work revealed that the protein has glycoside hydrolase activity. Previous work on the Dictyostelium discoideum homolog of human CLN5, Cln5, revealed its secretion during the early stages of development and its role in regulating cell adhesion and cAMP-mediated chemotaxis. Here, we used Dictyostelium to examine the effect of cln5-deficiency on various growth and developmental processes during the life cycle. During growth, cln5– cells displayed reduced cell proliferation, cytokinesis, viability, and folic acid-mediated chemotaxis. In addition, the growth of cln5– cells was severely impaired in nutrient-limiting media. Based on these findings, we assessed autophagic flux in growth-phase cells and observed that loss of cln5 increased the number of autophagosomes suggesting that the basal level of autophagy was increased in cln5– cells. Similarly, loss of cln5 increased the amounts of ubiquitin-positive proteins. During the early stages of multicellular development, the aggregation of cln5– cells was delayed and loss of the autophagy genes, atg1 and atg9, reduced the extracellular amount of Cln5. We also observed an increased amount of intracellular Cln5 in cells lacking the Dictyostelium homolog of the human glycoside hydrolase, hexosaminidase A (HEXA), further supporting the glycoside hydrolase activity of Cln5. This observation was also supported by our finding that CLN5 and HEXA expression are highly correlated in human tissues. Following mound formation, cln5– development was precocious and loss of cln5 affected spore morphology, germination, and viability. When cln5– cells were developed in the presence of the autophagy inhibitor ammonium chloride, the formation of multicellular structures was impaired, and the size of cln5– slugs was reduced relative to WT slugs. These results, coupled with the aberrant autophagic flux observed in cln5– cells during growth, support a role for Cln5 in autophagy during the Dictyostelium life cycle. In total, this study highlights the multifaceted role of Cln5 in Dictyostelium and provides insight into the pathological mechanisms that may underlie CLN5 disease.
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Affiliation(s)
- Meagan D McLaren
- Environmental and Life Sciences Graduate Program, Trent University, Peterborough, ON, Canada
| | | | - William D Kim
- Environmental and Life Sciences Graduate Program, Trent University, Peterborough, ON, Canada
| | - Shyong Q Yap
- Environmental and Life Sciences Graduate Program, Trent University, Peterborough, ON, Canada
| | - Robert J Huber
- Department of Biology, Trent University, Peterborough, ON, Canada
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10
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Yamada Y, Schaap P. The proppin Bcas3 and its interactor KinkyA localize to the early phagophore and regulate autophagy. Autophagy 2021; 17:640-655. [PMID: 32116088 PMCID: PMC8032249 DOI: 10.1080/15548627.2020.1725403] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Revised: 01/23/2020] [Accepted: 01/29/2020] [Indexed: 11/11/2022] Open
Abstract
To resolve the signaling mechanisms that mediate the starvation-induced processes of Dictyostelium sporulation and encystation, we performed insertional mutagenesis on cells harboring an mRFP-tagged spore gene. We isolated a mutant in kinkyA (knkA), a gene without known function, which formed fruiting bodies with a kinked stalk and lacking viable spores. Immunoprecipitation of lysates of KnkA-YFP-transformed knkA- cells yielded a mammalian BCAS3 homolog as a KnkA interactor. bcas3- phenocopied knkA- and Bcas3 colocalized with KnkA to puncta. Bcas3 shares sequence similarity with proppins (beta-propellors that bind phosphoinositides). Mutation of 2 Bcas3 residues that are essential for PtdIns3P binding in proppins prevented Bcas3 binding to PtdIns3P as well as punctate Bcas3 and KnkA localization. KnkA puncta also colocalized with small but not large vesicles that contain the autophagy protein Atg8 and were contiguous with the endoplasmic reticulum. knkA- and bcas3- cells showed a pronounced decrease of RFP-GFP-Atg8 in neutral early autophagosomes, indicating that KnkA and Bcas3 are required for macroautophagy/autophagy. Knockouts in atg7, atg5 or atg9 substantiated this finding by showing similar sporulation defects as knkA- and bcas3-. Defective Dictyostelium sporulation is evidently a useful diagnostic tool for the discovery of novel autophagy genes.Abbreviations: Atg: Autophagy-related; BCAS3: BCAS3 microtubule associated cell migration factor; cAMP: 3',5'-cyclic adenosine monophosphate; ER: endoplasmic reticulum; GFP: green fluorescent protein; PAS: phagophore assembly site; PRKA/PKA: protein kinase cAMP-dependent; Proppin: beta-propellers that bind phosphoinositides; PtdIns3P: phosphatidylinositol 3-phosphate; REMI: restriction enzyme-mediated insertional mutagenesis; RFP: red fluorescent protein; RT-qPCR: reverse transcriptase - quantitative polymerase chain reaction; WIPI: WD repeat domain, phosphoinositide interacting; YFP: yellow fluorescent protein.
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Affiliation(s)
- Yoko Yamada
- School of Life Sciences, University of Dundee, Dundee, UK
- Department of Biology, Faculty of Science, Toho University, Funabashi, Japan
| | - Pauline Schaap
- School of Life Sciences, University of Dundee, Dundee, UK
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11
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McGirr JA, Martin CH. Ecological divergence in sympatry causes gene misexpression in hybrids. Mol Ecol 2020; 29:2707-2721. [PMID: 32557903 DOI: 10.1111/mec.15512] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 05/21/2020] [Accepted: 06/01/2020] [Indexed: 12/17/2022]
Abstract
Ecological speciation occurs when reproductive isolation evolves as a byproduct of adaptive divergence between populations. Selection favouring gene regulatory divergence between species could result in transgressive levels of gene expression in F1 hybrids that may lower hybrid fitness. We combined 58 resequenced genomes with 124 transcriptomes to identify patterns of hybrid gene misexpression that may be driven by adaptive regulatory divergence within a young radiation of Cyprinodon pupfishes, which consists of a dietary generalist and two trophic specialists-a molluscivore and a scale-eater. We found more differential gene expression between closely related sympatric specialists than between allopatric generalist populations separated by 1,000 km. Intriguingly, 9.6% of genes that were differentially expressed between sympatric species were also misexpressed in F1 hybrids. A subset of these genes were in highly differentiated genomic regions and enriched for functions important for trophic specialization, including head, muscle and brain development. These regions also included genes that showed evidence of hard selective sweeps and were significantly associated with oral jaw length-the most rapidly diversifying skeletal trait in this radiation. Our results indicate that divergent ecological selection in sympatry can contribute to hybrid gene misexpression which may act as a reproductive barrier between nascent species.
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Affiliation(s)
- Joseph A McGirr
- Department of Biology, University of North Carolina, Chapel Hill, NC
| | - Christopher H Martin
- Department of Biology, University of North Carolina, Chapel Hill, NC.,Department of Integrative Biology and Museum of Vertebrate Zoology, University of California, Berkeley, CA
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12
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Karow M, Fischer S, Meßling S, Konertz R, Riehl J, Xiong Q, Rijal R, Wagle P, S. Clemen C, Eichinger L. Functional Characterisation of the Autophagy ATG12~5/16 Complex in Dictyostelium discoideum. Cells 2020; 9:cells9051179. [PMID: 32397394 PMCID: PMC7290328 DOI: 10.3390/cells9051179] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Revised: 05/04/2020] [Accepted: 05/06/2020] [Indexed: 12/21/2022] Open
Abstract
Macroautophagy, a highly conserved and complex intracellular degradative pathway, involves more than 20 core autophagy (ATG) proteins, among them the hexameric ATG12~5/16 complex, which is part of the essential ubiquitin-like conjugation systems in autophagy. Dictyostelium discoideumatg5 single, atg5/12 double, and atg5/12/16 triple gene knock-out mutant strains displayed similar defects in the conjugation of ATG8 to phosphatidylethanolamine, development, and cell viability upon nitrogen starvation. This implies that ATG5, 12 and 16 act as a functional unit in canonical autophagy. Macropinocytosis of TRITC dextran and phagocytosis of yeast were significantly decreased in ATG5¯ and ATG5¯/12¯ and even further in ATG5¯/12¯/16¯ cells. In contrast, plaque growth on Klebsiella aerogenes was about twice as fast for ATG5¯ and ATG5¯/12¯/16¯ cells in comparison to AX2, but strongly decreased for ATG5¯/12¯ cells. Along this line, phagocytic uptake of Escherichia coli was significantly reduced in ATG5¯/12¯ cells, while no difference in uptake, but a strong increase in membrane association of E. coli, was seen for ATG5¯ and ATG5¯/12¯/16¯ cells. Proteasomal activity was also disturbed in a complex fashion, consistent with an inhibitory activity of ATG16 in the absence of ATG5 and/or ATG12. Our results confirm the essential function of the ATG12~5/16 complex in canonical autophagy, and furthermore are consistent with autophagy-independent functions of the complex and its individual components. They also strongly support the placement of autophagy upstream of the ubiquitin-proteasome system (UPS), as a fully functional UPS depends on autophagy.
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Affiliation(s)
- Malte Karow
- Centre for Biochemistry, Institute of Biochemistry I, Medical Faculty, University of Cologne, 50931 Cologne, Germany; (M.K.); (S.F.); (S.M.); (R.K.); (J.R.)
| | - Sarah Fischer
- Centre for Biochemistry, Institute of Biochemistry I, Medical Faculty, University of Cologne, 50931 Cologne, Germany; (M.K.); (S.F.); (S.M.); (R.K.); (J.R.)
| | - Susanne Meßling
- Centre for Biochemistry, Institute of Biochemistry I, Medical Faculty, University of Cologne, 50931 Cologne, Germany; (M.K.); (S.F.); (S.M.); (R.K.); (J.R.)
| | - Roman Konertz
- Centre for Biochemistry, Institute of Biochemistry I, Medical Faculty, University of Cologne, 50931 Cologne, Germany; (M.K.); (S.F.); (S.M.); (R.K.); (J.R.)
| | - Jana Riehl
- Centre for Biochemistry, Institute of Biochemistry I, Medical Faculty, University of Cologne, 50931 Cologne, Germany; (M.K.); (S.F.); (S.M.); (R.K.); (J.R.)
| | - Qiuhong Xiong
- Institute of Biomedical Sciences, Shanxi University, No. 92 Wucheng Road, Taiyuan 030006, China;
| | - Ramesh Rijal
- Department of Biology, Texas A&M University, College Station, TX 77843-3474, USA;
| | - Prerana Wagle
- Bioinformatics Core Facility, CECAD Research Center, University of Cologne, 50931 Cologne, Germany;
| | - Christoph S. Clemen
- Institute of Aerospace Medicine, German Aerospace Center (DLR), 51147 Cologne, Germany;
- Center for Physiology and Pathophysiology, Institute of Vegetative Physiology, Medical Faculty, University of Cologne, 50931 Cologne, Germany
- Institute of Neuropathology, University Hospital Erlangen, Friedrich-Alexander University Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Ludwig Eichinger
- Centre for Biochemistry, Institute of Biochemistry I, Medical Faculty, University of Cologne, 50931 Cologne, Germany; (M.K.); (S.F.); (S.M.); (R.K.); (J.R.)
- Correspondence: ; Tel.: +49-221-478-6928; Fax: +49-221-478-97524
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13
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O'Day DH, Mathavarajah S, Myre MA, Huber RJ. Calmodulin-mediated events during the life cycle of the amoebozoan Dictyostelium discoideum. Biol Rev Camb Philos Soc 2020; 95:472-490. [PMID: 31774219 PMCID: PMC7079120 DOI: 10.1111/brv.12573] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Revised: 10/30/2019] [Accepted: 11/11/2019] [Indexed: 12/14/2022]
Abstract
This review focusses on the functions of intracellular and extracellular calmodulin, its target proteins and their binding proteins during the asexual life cycle of Dictyostelium discoideum. Calmodulin is a primary regulatory protein of calcium signal transduction that functions throughout all stages. During growth, it mediates autophagy, the cell cycle, folic acid chemotaxis, phagocytosis, and other functions. During mitosis, specific calmodulin-binding proteins translocate to alternative locations. Translocation of at least one cell adhesion protein is calmodulin dependent. When starved, cells undergo calmodulin-dependent chemotaxis to cyclic AMP generating a multicellular pseudoplasmodium. Calmodulin-dependent signalling within the slug sets up a defined pattern and polarity that sets the stage for the final events of morphogenesis and cell differentiation. Transected slugs undergo calmodulin-dependent transdifferentiation to re-establish the disrupted pattern and polarity. Calmodulin function is critical for stalk cell differentiation but also functions in spore formation, events that begin in the pseudoplasmodium. The asexual life cycle restarts with the calmodulin-dependent germination of spores. Specific calmodulin-binding proteins as well as some of their binding partners have been linked to each of these events. The functions of extracellular calmodulin during growth and development are also discussed. This overview brings to the forefront the central role of calmodulin, working through its numerous binding proteins, as a primary downstream regulator of the critical calcium signalling pathways that have been well established in this model eukaryote. This is the first time the function of calmodulin and its target proteins have been documented through the complete life cycle of any eukaryote.
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Affiliation(s)
- Danton H. O'Day
- Cell and Systems BiologyUniversity of TorontoTorontoOntarioM5S 3G5Canada
- Department of BiologyUniversity of Toronto MississaugaMississaugaOntarioL5L 1C6Canada
| | | | - Michael A. Myre
- Department of Biological Sciences, Kennedy College of SciencesUniversity of Massachusetts LowellLowellMassachusetts01854USA
| | - Robert J. Huber
- Department of BiologyTrent UniversityPeterboroughOntarioK9L 0G2Canada
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14
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Joshi V, Upadhyay A, Prajapati VK, Mishra A. How autophagy can restore proteostasis defects in multiple diseases? Med Res Rev 2020; 40:1385-1439. [PMID: 32043639 DOI: 10.1002/med.21662] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Revised: 01/03/2020] [Accepted: 01/28/2020] [Indexed: 12/12/2022]
Abstract
Cellular evolution develops several conserved mechanisms by which cells can tolerate various difficult conditions and overall maintain homeostasis. Autophagy is a well-developed and evolutionarily conserved mechanism of catabolism, which endorses the degradation of foreign and endogenous materials via autolysosome. To decrease the burden of the ubiquitin-proteasome system (UPS), autophagy also promotes the selective degradation of proteins in a tightly regulated way to improve the physiological balance of cellular proteostasis that may get perturbed due to the accumulation of misfolded proteins. However, the diverse as well as selective clearance of unwanted materials and regulations of several cellular mechanisms via autophagy is still a critical mystery. Also, the failure of autophagy causes an increase in the accumulation of harmful protein aggregates that may lead to neurodegeneration. Therefore, it is necessary to address this multifactorial threat for in-depth research and develop more effective therapeutic strategies against lethal autophagy alterations. In this paper, we discuss the most relevant and recent reports on autophagy modulations and their impact on neurodegeneration and other complex disorders. We have summarized various pharmacological findings linked with the induction and suppression of autophagy mechanism and their promising preclinical and clinical applications to provide therapeutic solutions against neurodegeneration. The conclusion, key questions, and future prospectives sections summarize fundamental challenges and their possible feasible solutions linked with autophagy mechanism to potentially design an impactful therapeutic niche to treat neurodegenerative diseases and imperfect aging.
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Affiliation(s)
- Vibhuti Joshi
- Cellular and Molecular Neurobiology Unit, Indian Institute of Technology Jodhpur, Karwar, India
| | - Arun Upadhyay
- Cellular and Molecular Neurobiology Unit, Indian Institute of Technology Jodhpur, Karwar, India
| | - Vijay K Prajapati
- Department of Biochemistry, School of Life Sciences, Central University of Rajasthan, Ajmer, India
| | - Amit Mishra
- Cellular and Molecular Neurobiology Unit, Indian Institute of Technology Jodhpur, Karwar, India
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15
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Maurya R, Kumar R, Saran S. AMPKα promotes basal autophagy induction in Dictyostelium discoideum. J Cell Physiol 2019; 235:4941-4953. [PMID: 31680241 DOI: 10.1002/jcp.29373] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Accepted: 10/07/2019] [Indexed: 01/24/2023]
Abstract
Autophagy is a degradation process, wherein long-lived proteins, damaged organelles, and protein aggregates are degraded to maintain cellular homeostasis. Upon starvation, 5'-AMP-activated protein kinase (AMPK) initiates autophagy. We show that ampkα- cells exhibit 50% reduction in pinocytosis and display defective phagocytosis. Re-expression of AMPKα in ampkα- cells co-localizes with red fluorescence protein-tagged bacteria. The ampkα- cells show reduced cell survival and autophagic flux under basal and starvation conditions. Co-immunoprecipitation studies show conservation of the AMPK-ATG1 axis in basal autophagy. Computational analyses suggest that the N-terminal region of DdATG1 is amenable for interaction with AMPK. Furthermore, β-actin was found to be a novel interacting partner of AMPK, attributed to the alteration in macropinocytosis and phagocytosis in the absence of AMPK. Additionally, ampkα- cells exhibit enhanced poly-ubiquitinated protein levels and allied large ubiquitin-positive protein aggregates. Our findings suggest that AMPK provides links among pinocytosis, phagocytosis, autophagy, and is a requisite for basal autophagy in Dictyostelium.
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Affiliation(s)
- Ranjana Maurya
- Molecular Cell and Developmental Biology Lab, School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Rakesh Kumar
- Molecular Cell and Developmental Biology Lab, School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Shweta Saran
- Molecular Cell and Developmental Biology Lab, School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
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16
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Santarriaga S, Fikejs A, Scaglione J, Scaglione KM. A Heat Shock Protein 48 (HSP48) Biomolecular Condensate Is Induced during Dictyostelium discoideum Development. mSphere 2019; 4:e00314-19. [PMID: 31217303 PMCID: PMC6584373 DOI: 10.1128/msphere.00314-19] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Accepted: 06/04/2019] [Indexed: 11/20/2022] Open
Abstract
The social amoeba Dictyostelium discoideum's proteome contains a vast array of simple sequence repeats, providing a unique model to investigate proteostasis. Upon conditions of cellular stress, D. discoideum undergoes a developmental process, transitioning from a unicellular amoeba to a multicellular fruiting body. Little is known about how proteostasis is maintained during D. discoideum's developmental process. Here, we have identified a novel α-crystallin domain-containing protein, heat shock protein 48 (HSP48), that is upregulated during D. discoideum development. HSP48 functions in part by forming a biomolecular condensate via its highly positively charged intrinsically disordered carboxy terminus. In addition to HSP48, the highly negatively charged primordial chaperone polyphosphate is also upregulated during D. discoideum development, and polyphosphate functions to stabilize HSP48. Upon germination, levels of both HSP48 and polyphosphate dramatically decrease, consistent with a role for HSP48 and polyphosphate during development. Together, our data demonstrate that HSP48 is strongly induced during Dictyostelium discoideum development. We also demonstrate that HSP48 forms a biomolecular condensate and that polyphosphate is necessary to stabilize the HSP48 biomolecular condensate.IMPORTANCE During cellular stress, many microbes undergo a transition to a dormant state. This includes the social amoeba Dictyostelium discoideum that transitions from a unicellular amoeba to a multicellular fruiting body upon starvation. In this work, we identify heat shock protein 48 (HSP48) as a chaperone that is induced during development. We also show that HSP48 forms a biomolecular condensate and is stabilized by polyphosphate. The findings here identify Dictyostelium discoideum as a novel microbe to investigate protein quality control pathways during the transition to dormancy.
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Affiliation(s)
| | - Alicia Fikejs
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Jamie Scaglione
- Department of Computational and Physical Sciences, Carroll University, Waukesha, Wisconsin, USA
| | - K Matthew Scaglione
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
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17
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Yamada Y, Schaap P. Cyclic AMP induction of Dictyostelium prespore gene expression requires autophagy. Dev Biol 2019; 452:114-126. [PMID: 31051160 PMCID: PMC6598861 DOI: 10.1016/j.ydbio.2019.04.017] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2019] [Revised: 04/06/2019] [Accepted: 04/25/2019] [Indexed: 12/27/2022]
Abstract
Dictyostelium discoideum amoebas display colonial multicellularity where starving amoebas aggregate to form migrating slugs and fruiting bodies consisting of spores and three supporting cell types. To resolve the cell signalling mechanism that control sporulation, we use insertional mutagenesis of amoebas transformed with fusion constructs of spore genes and red fluorescent protein. We identified the defective gene in a mutant lacking spore gene expression as the autophagy gene Atg7. Directed knock-out of atg7 and of autophagy genes like atg5 and atg9 yielded a similar phenotype, with lack of viable spores and excessive differentiation of stalk cells. The atg7-, atg5- and atg9- cells were specifically defective in cAMP induction of prespore genes, but showed enhanced cAMP stimulation of prestalk genes at the same developmental stage. The lack of prespore gene induction in the autophagy mutants was not due to deleterious effects of loss of autophagy on known components of the cAMP pathway, such as cAMP receptors and their cAMP-induced phosphorylation and internalization, PKA and the transcription factors SpaA and GbfA, or to lack of NH3 production by proteolysis, which was previously suggested to stimulate the spore pathway. Our continued mutagenesis approach is the most likely to yield the intriguing link between autophagy and prespore gene induction. A screen for Dictyostelium sporulation mutants identified autophagy gene atg7. Atg7-, atg5-and atg9-cells cannot form viable spores, but show normal stalk formation. Atg7-, atg5-and atg9-are specifically defective in cAMP induction of prespore genes. Atg7-, atg5-and atg9-show normal to enhanced cAMP induction of prestalk genes. PKA overexpression does not restore sporulation in autophagy mutants.
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Affiliation(s)
- Yoko Yamada
- School of Life Sciences, University of Dundee, DD15EH, Dundee, UK
| | - Pauline Schaap
- School of Life Sciences, University of Dundee, DD15EH, Dundee, UK.
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18
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Sharma D, Otto G, Warren EC, Beesley P, King JS, Williams RSB. Gamma secretase orthologs are required for lysosomal activity and autophagic degradation in Dictyostelium discoideum, independent of PSEN (presenilin) proteolytic function. Autophagy 2019; 15:1407-1418. [PMID: 30806144 PMCID: PMC6613883 DOI: 10.1080/15548627.2019.1586245] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Mutations in the γ-secretase complex are strongly associated with familial Alzheimer disease. Both proteolytic and non-proteolytic functions for the γ-secretase complex have been previously described in mammalian model organisms, but their relative contributions to disease pathology remain unclear. Here, we dissect the roles of orthologs of the γ-secretase components in the model system Dictyostelium, focusing on endocytosis, lysosomal activity and autophagy. In this model, we show that the orthologs of PSEN (psenA and psenB), Ncstn (nicastrin) and Aph-1 (gamma-secretase subunit Aph-1), are necessary for optimal fluid-phase uptake by macropinocytosis and in multicellular development under basic pH conditions. Disruption of either psenA/B or Aph-1 proteins also leads to disrupted phagosomal proteolysis as well as decreased autophagosomal acidification and autophagic flux. This indicates a general defect in lysosomal trafficking and degradation, which we show leads to the accumulation of ubiquitinated protein aggregates in cells lacking psenA/B and Aph-1 proteins. Importantly, we find that all the endocytic defects observed in Dictyostelium PSEN ortholog mutants can be fully rescued by proteolytically inactive Dictyostelium psenB and human PSEN1 proteins. Our data therefore demonstrates an evolutionarily conserved non-proteolytic role for presenilin, and γ-secretase component orthologs, in maintaining Dictyostelium lysosomal trafficking and autophagy. Abbreviations: Atg8: autophagy protein 8a; Aph-1: gamma-secretase subunit Aph-1; crtA: calreticulin; ER: endoplasmic reticulum; GFP: green fluorescent protein; GSK3B: glycogen synthase kinase 3 beta; Ncstn: nicastrin; PSEN1: presenilin 1; psenA and psenB: Dictyostelium presenilin A and B; TRITC; tetramethylrhodamine isothiocyanate.
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Affiliation(s)
- Devdutt Sharma
- a School of Biological Sciences , Royal Holloway, University of London , Egham , UK
| | - Grant Otto
- a School of Biological Sciences , Royal Holloway, University of London , Egham , UK
| | - Eleanor C Warren
- a School of Biological Sciences , Royal Holloway, University of London , Egham , UK
| | - Philip Beesley
- a School of Biological Sciences , Royal Holloway, University of London , Egham , UK
| | - Jason S King
- b Department of Biomedical Sciences , University of Sheffield , Sheffield , UK
| | - Robin S B Williams
- a School of Biological Sciences , Royal Holloway, University of London , Egham , UK
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19
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Muñoz-Braceras S, Tornero-Écija AR, Vincent O, Escalante R. VPS13A is closely associated with mitochondria and is required for efficient lysosomal degradation. Dis Model Mech 2019; 12:dmm036681. [PMID: 30709847 PMCID: PMC6398486 DOI: 10.1242/dmm.036681] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Accepted: 01/22/2019] [Indexed: 12/11/2022] Open
Abstract
Members of the VPS13 family are associated with various human diseases. In particular, the loss of function of VPS13A leads to chorea-acanthocytosis (ChAc), a rare neurodegenerative disease without available curative treatments. Autophagy has been considered a promising therapeutic target because the absence of VPS13A causes a defective autophagy flux. However, the mechanistic details of this deficiency are unknown. Here, we identified Rab7A as an interactor of one of the VPS13 family members in Dictyostelium discoideum and showed that this interaction is conserved between the human homologs VPS13A and RAB7A in HeLa cells. As RAB7A is a key player in endosome trafficking, we addressed the possible function of VPS13A in endosome dynamics and lysosome degradation. Our results suggest that the decrease in autophagy observed in the absence of VPS13A may be the result of a more general defect in endocytic trafficking and lysosomal degradation. Unexpectedly, we found that VPS13A is closely localized to mitochondria, suggesting that the role of VPS13A in the endolysosomal pathway might be related to inter-organelle communication. We show that VPS13A localizes at the interface between mitochondria-endosomes and mitochondria-endoplasmic reticulum and that the presence of membrane contact sites is altered in the absence of VPS13A. Based on these findings, we propose that therapeutic strategies aimed at modulating the endolysosomal pathway could be beneficial in the treatment of ChAc.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Sandra Muñoz-Braceras
- Instituto de Investigaciones Biomédicas Alberto Sols, Department of Experimental Models of Human Diseases, Consejo Superior de Investigaciones Científicas (CSIC)/Universidad Autónoma Madrid (UAM), 28029-Madrid, Spain
| | - Alba R Tornero-Écija
- Instituto de Investigaciones Biomédicas Alberto Sols, Department of Experimental Models of Human Diseases, Consejo Superior de Investigaciones Científicas (CSIC)/Universidad Autónoma Madrid (UAM), 28029-Madrid, Spain
| | - Olivier Vincent
- Instituto de Investigaciones Biomédicas Alberto Sols, Department of Experimental Models of Human Diseases, Consejo Superior de Investigaciones Científicas (CSIC)/Universidad Autónoma Madrid (UAM), 28029-Madrid, Spain
| | - Ricardo Escalante
- Instituto de Investigaciones Biomédicas Alberto Sols, Department of Experimental Models of Human Diseases, Consejo Superior de Investigaciones Científicas (CSIC)/Universidad Autónoma Madrid (UAM), 28029-Madrid, Spain
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20
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Functional Characterization of Ubiquitin-Like Core Autophagy Protein ATG12 in Dictyostelium discoideum. Cells 2019; 8:cells8010072. [PMID: 30669443 PMCID: PMC6356199 DOI: 10.3390/cells8010072] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 01/15/2019] [Accepted: 01/17/2019] [Indexed: 12/12/2022] Open
Abstract
Autophagy is a highly conserved intracellular degradative pathway that is crucial for cellular homeostasis. During autophagy, the core autophagy protein ATG12 plays, together with ATG5 and ATG16, an essential role in the expansion of the autophagosomal membrane. In this study we analyzed gene replacement mutants of atg12 in Dictyostelium discoideum AX2 wild-type and ATG16‾ cells. RNAseq analysis revealed a strong enrichment of, firstly, autophagy genes among the up-regulated genes and, secondly, genes implicated in cell motility and phagocytosis among the down-regulated genes in the generated ATG12‾, ATG16‾ and ATG12‾/16‾ cells. The mutant strains showed similar defects in fruiting body formation, autolysosome maturation, and cellular viability, implying that ATG12 and ATG16 act as a functional unit in canonical autophagy. In contrast, ablation of ATG16 or of ATG12 and ATG16 resulted in slightly more severe defects in axenic growth, macropinocytosis, and protein homeostasis than ablation of only ATG12, suggesting that ATG16 fulfils an additional function in these processes. Phagocytosis of yeast, spore viability, and maximal cell density were much more affected in ATG12‾/16‾ cells, indicating that both proteins also have cellular functions independent of each other. In summary, we show that ATG12 and ATG16 fulfil autophagy-independent functions in addition to their role in canonical autophagy.
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21
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Xiong Q, Li W, Li P, Yang M, Wu C, Eichinger L. The Role of ATG16 in Autophagy and The Ubiquitin Proteasome System. Cells 2018; 8:cells8010002. [PMID: 30577509 PMCID: PMC6356889 DOI: 10.3390/cells8010002] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Revised: 12/17/2018] [Accepted: 12/18/2018] [Indexed: 02/07/2023] Open
Abstract
Autophagy and the ubiquitin proteasome system (UPS) are the two major cellular degradation pathways, which are critical for the maintenance of cell homeostasis. The two pathways differ in their mechanisms and clients. The evolutionary conserved ATG16 plays a key role in autophagy and appears to link autophagy with the UPS. Here, we review the role of ATG16 in different species. We summarize the current knowledge of its functions in autophagosome membrane expansion and autophagosome formation, in Crohn’s disease, and in bacterial sequestration. In addition, we provide information on its autophagy-independent functions and its role in the crosstalk between autophagy and the UPS.
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Affiliation(s)
- Qiuhong Xiong
- Institute of Biomedical Sciences, Shanxi University, No.92 Wucheng Road, Taiyuan 030006, China.
| | - Wenjing Li
- Institute of Biomedical Sciences, Shanxi University, No.92 Wucheng Road, Taiyuan 030006, China.
| | - Ping Li
- Institute of Biomedical Sciences, Shanxi University, No.92 Wucheng Road, Taiyuan 030006, China.
| | - Min Yang
- Institute of Biomedical Sciences, Shanxi University, No.92 Wucheng Road, Taiyuan 030006, China.
| | - Changxin Wu
- Institute of Biomedical Sciences, Shanxi University, No.92 Wucheng Road, Taiyuan 030006, China.
| | - Ludwig Eichinger
- Center for Biochemistry, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Cologne, Germany.
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22
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Xiong Q, Fischer S, Karow M, Müller R, Meßling S, Eichinger L. ATG16 mediates the autophagic degradation of the 19S proteasomal subunits PSMD1 and PSMD2. Eur J Cell Biol 2018; 97:523-532. [PMID: 30269947 DOI: 10.1016/j.ejcb.2018.09.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Revised: 08/06/2018] [Accepted: 09/10/2018] [Indexed: 12/27/2022] Open
Abstract
Autophagy and the ubiquitin proteasome system are the two major cellular processes for protein and organelle recycling and clearance in eukaryotic cells. Evidence is accumulating that these two pathways are interrelated through adaptor proteins. Here, we found that PSMD1 and PSMD2, both components of the 19S regulatory particle of the proteasome, directly interact with Dictyostelium discoideum autophagy 16 (ATG16), a core autophagosomal protein. ATG16 is composed of an N-terminal domain, which is responsible for homo-dimerization and binding to ATG5 and a C-terminal β-propeller structure. Deletion analysis of ATG16 showed that the N-terminal half of ATG16 interacted directly only with PSMD1, while the C-terminal half interacted with both, PSMD1 and PSMD2. RFP-tagged PSMD1 as well as PSMD2 were enriched in large puncta, reminiscent of autophagosomes, in wild-type cells. These puncta were absent in atg16‾ and atg9‾/16‾ cells and weaker and less frequent in atg9‾ cells, showing that ATG16 was crucial and the autophagic process important for their formation. Co-expression of ATG16-GFP or GFP-ATG8a(LC3) with RFP-PSMD1 or RFP-PSMD2, respectively, in atg16‾ or wild-type cells revealed many instances of co-localization, suggesting that RFP-PSMD1 or RFP-PSMD2 positive puncta constitute autophagosomes. LysoTracker® labeling and a proteolytic cleavage assay confirmed that PSMD1 and PSMD2 were present in lysosomes in wild-type cells. In vivo, ATG16 is required for their enrichment in ATG8a positive puncta, which mature into autolysosomes. We propose that ATG16 links autophagy and the ubiquitin proteasome system.
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Affiliation(s)
- Qiuhong Xiong
- Center for Biochemistry, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Cologne, Germany.; Institute of Biomedical Sciences, Shanxi University, No. 92 Wucheng Road, 030006 Taiyuan, Shanxi, China
| | - Sarah Fischer
- Center for Biochemistry, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Cologne, Germany
| | - Malte Karow
- Center for Biochemistry, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Cologne, Germany
| | - Rolf Müller
- Center for Biochemistry, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Cologne, Germany
| | - Susanne Meßling
- Center for Biochemistry, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Cologne, Germany
| | - Ludwig Eichinger
- Center for Biochemistry, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Cologne, Germany..
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Lohia R, Jain P, Jain M, Mishra H, Burma PK, Shrivastava A, Saran S. Deletion of Dictyostelium discoideum Sir2A impairs cell proliferation and inhibits autophagy. J Biosci 2018. [DOI: 10.1007/s12038-018-9753-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Cardenal-Muñoz E, Barisch C, Lefrançois LH, López-Jiménez AT, Soldati T. When Dicty Met Myco, a (Not So) Romantic Story about One Amoeba and Its Intracellular Pathogen. Front Cell Infect Microbiol 2018; 7:529. [PMID: 29376033 PMCID: PMC5767268 DOI: 10.3389/fcimb.2017.00529] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Accepted: 12/18/2017] [Indexed: 01/06/2023] Open
Abstract
In recent years, Dictyostelium discoideum has become an important model organism to study the cell biology of professional phagocytes. This amoeba not only shares many molecular features with mammalian macrophages, but most of its fundamental signal transduction pathways are conserved in humans. The broad range of existing genetic and biochemical tools, together with its suitability for cell culture and live microscopy, make D. discoideum an ideal and versatile laboratory organism. In this review, we focus on the use of D. discoideum as a phagocyte model for the study of mycobacterial infections, in particular Mycobacterium marinum. We look in detail at the intracellular cycle of M. marinum, from its uptake by D. discoideum to its active or passive egress into the extracellular medium. In addition, we describe the molecular mechanisms that both the mycobacterial invader and the amoeboid host have developed to fight against each other, and compare and contrast with those developed by mammalian phagocytes. Finally, we introduce the methods and specific tools that have been used so far to monitor the D. discoideum-M. marinum interaction.
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Affiliation(s)
- Elena Cardenal-Muñoz
- Department of Biochemistry, Sciences II, Faculty of Sciences, University of Geneva, Geneva, Switzerland
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25
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Effect of Multipurpose Solution Combined With Autophagy Inhibitors on Adhesion of Acanthamoeba trophozoites to Silicone Hydrogel Contact Lenses. Cornea 2017; 36:1538-1543. [DOI: 10.1097/ico.0000000000001340] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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26
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Methods to Monitor and Quantify Autophagy in the Social Amoeba Dictyostelium discoideum. Cells 2017; 6:cells6030018. [PMID: 28671610 PMCID: PMC5617964 DOI: 10.3390/cells6030018] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Revised: 06/27/2017] [Accepted: 06/28/2017] [Indexed: 12/30/2022] Open
Abstract
Autophagy is a eukaryotic catabolic pathway that degrades and recycles cellular components to maintain homeostasis. It can target protein aggregates, superfluous biomolecular complexes, dysfunctional and damaged organelles, as well as pathogenic intracellular microbes. Autophagy is a dynamic process in which the different stages from initiation to final degradation of cargo are finely regulated. Therefore, the study of this process requires the use of a palette of techniques, which are continuously evolving and whose interpretation is not trivial. Here, we present the social amoeba Dictyostelium discoideum as a relevant model to study autophagy. Several methods have been developed based on the tracking and observation of autophagosomes by microscopy, analysis of changes in expression of autophagy genes and proteins, and examination of the autophagic flux with various techniques. In this review, we discuss the pros and cons of the currently available techniques to assess autophagy in this organism.
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Martínez-García R, Tarnita CE. Seasonality can induce coexistence of multiple bet-hedging strategies in Dictyostelium discoideum via storage effect. J Theor Biol 2017; 426:104-116. [PMID: 28536035 DOI: 10.1016/j.jtbi.2017.05.019] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2016] [Revised: 05/05/2017] [Accepted: 05/17/2017] [Indexed: 02/06/2023]
Abstract
The social amoeba Dictyostelium discoideum has been recently suggested as an example of bet-hedging in microbes. In the presence of resources, amoebae reproduce as unicellular organisms. Resource depletion, however, leads to a starvation phase in which the population splits between aggregators, which form a fruiting body made of a stalk and resistant spores, and non-aggregators, which remain as vegetative cells. Spores are favored when starvation periods are long, but vegetative cells can exploit resources in environments where food replenishes quickly. The investment in aggregators versus non-aggregators can therefore be understood as a bet-hedging strategy that evolves in response to stochastic starvation times. A genotype (or strategy) is defined by the balance between each type of cells. In this framework, if the ecological conditions on a patch are defined in terms of the mean starvation time (i.e. time between the onset of starvation and the arrival of a new food pulse), a single genotype dominates each environment, which is inconsistent with the huge genetic diversity observed in nature. Here we investigate whether seasonality, represented by a periodic, wet-dry alternation in the mean starvation times, allows the coexistence of several strategies in a single patch. We study this question in a non-spatial (well-mixed) setting in which different strains compete for a common pool of resources over a sequence of growth-starvation cycles. We find that seasonality induces a temporal storage effect that can promote the stable coexistence of multiple genotypes. Two conditions need to be met in our model. First, there has to be a temporal niche partitioning (two well-differentiated habitats within the year), which requires not only different mean starvation times between seasons but also low variance within each season. Second, each season's well-adapted strain has to grow and create a large enough population that permits its survival during the subsequent unfavorable season, which requires the number of growth-starvation cycles within each season to be sufficiently large. These conditions allow the coexistence of two bet-hedging strategies. Additional tradeoffs among life-history traits can expand the range of coexistence and increase the number of coexisting strategies, contributing toward explaining the genetic diversity observed in D. discoideum. Although focused on this cellular slime mold, our results are general and may be easily extended to other microbes.
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Affiliation(s)
- Ricardo Martínez-García
- Department of Ecology and Evolutionary Biology, Princeton University. Princeton NJ 08544, USA
| | - Corina E Tarnita
- Department of Ecology and Evolutionary Biology, Princeton University. Princeton NJ 08544, USA.
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Mycobacterium marinum antagonistically induces an autophagic response while repressing the autophagic flux in a TORC1- and ESX-1-dependent manner. PLoS Pathog 2017; 13:e1006344. [PMID: 28414774 PMCID: PMC5407849 DOI: 10.1371/journal.ppat.1006344] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Revised: 04/27/2017] [Accepted: 04/11/2017] [Indexed: 12/18/2022] Open
Abstract
Autophagy is a eukaryotic catabolic process also participating in cell-autonomous defence. Infected host cells generate double-membrane autophagosomes that mature in autolysosomes to engulf, kill and digest cytoplasmic pathogens. However, several bacteria subvert autophagy and benefit from its machinery and functions. Monitoring infection stages by genetics, pharmacology and microscopy, we demonstrate that the ESX-1 secretion system of Mycobacterium marinum, a close relative to M. tuberculosis, upregulates the transcription of autophagy genes, and stimulates autophagosome formation and recruitment to the mycobacteria-containing vacuole (MCV) in the host model organism Dictyostelium. Antagonistically, ESX-1 is also essential to block the autophagic flux and deplete the MCV of proteolytic activity. Activators of the TORC1 complex localize to the MCV in an ESX-1-dependent manner, suggesting an important role in the manipulation of autophagy by mycobacteria. Our findings suggest that the infection by M. marinum activates an autophagic response that is simultaneously repressed and exploited by the bacterium to support its survival inside the MCV. One of the cell-autonomous defence pathways against intracellular pathogens is autophagy, an ancestral eukaryotic process surprisingly conserved throughout evolution. Recent studies have highlighted contradictory roles for autophagy during mycobacterial infection. Whereas some studies revealed a role for autophagy to control intracellular bacterial growth, others brought evidence that mycobacteria somehow inhibit autophagic killing. Here, we demonstrate for the first time that Mycobacterium marinum induces both an early autophagic response and its simultaneous repression by blocking the autophagic digestion. This antagonistic manipulation of autophagy is dependent on a functional ESX-1-secretion system, which secretes the membrane-damaging factor ESAT-6, proposed to participate in the perforation of the M. marinum-containing vacuole (MCV). We show here that these membrane damages activate the formation of autophagosomes and their recruitment to the MCV. However, M. marinum also utilizes its ESX-1 secretion system to avoid killing inside autolysosomes by blocking the autophagic flux. In addition, we bring evidence that this manipulation of autophagy is orchestrated via the regulation of TORC1, the major eukaryotic kinase complex controlling nutrient-sensing and cell metabolism.
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Meßling S, Matthias J, Xiong Q, Fischer S, Eichinger L. The two Dictyostelium discoideum autophagy 8 proteins have distinct autophagic functions. Eur J Cell Biol 2017; 96:312-324. [PMID: 28413119 DOI: 10.1016/j.ejcb.2017.03.014] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Revised: 03/23/2017] [Accepted: 03/23/2017] [Indexed: 12/16/2022] Open
Abstract
Autophagy is a highly conserved cellular degradation pathway which is crucial for various cellular processes. The autophagic process is subdivided in the initiation, autophagosome maturation and lysosomal degradation phases and involves more than forty core and accessory autophagy-related (ATG) proteins. Autophagy 8 (ATG8, in mammals LC3) is a well-established marker of autophagy and is linked to the autophagic membrane from initiation until fusion with the lysosome. We generated single and double knock-out mutants of the two Dictyostelium paralogues, ATG8a and ATG8b, as well as strains that expressed RFP-ATG8a and/or GFP-ATG8b, RFP-ATG8b, RFP-GFP-ATG8a or RFP-GFP-ATG8b in different knock-out mutants. The ATG8b¯ mutant displayed only subtle phenotypic changes in comparison to AX2 wild-type cells. In contrast, deletion of ATG8a resulted in a complex phenotype with delayed development, reduced growth, phagocytosis and cell viability, an increase in ubiquitinylated proteins and a concomitant decrease in proteasomal activity. The phenotype of the ATG8a¯/b¯ strain was, except for cell viability, in all aforementioned aspects more severe, showing that both proteins function in parallel during most analysed cellular processes. Immunofluorescence analysis of knock-out strains expressing either RFP-GFP-ATG8a or RFP-GFP-ATG8b suggests a crucial function for ATG8b in autophagosome-lysosome fusion. Quantitative analysis of strains expressing RFP-ATG8a, RFP-ATG8b, or RFP-ATG8a and GFP-ATG8b revealed that ATG8b generally localised to small and large vesicles, whereas ATG8a preferentially co-localised with ATG8b on large vesicles, indicating that ATG8b associated with nascent autophagosomes before ATG8a, which is supported by previous results (Matthias et al., 2016). Deconvoluted confocal fluorescence images showed that ATG8b localised around ATG8a and was presumably mainly present on the outer membrane of the autophagosome while ATG8a appears to be mainly associated with the inner membrane. In summary, our data show that ATG8a and ATG8b have distinct functions and are involved in canonical as well as non-canonical autophagy. The data further suggest that ATG8b predominantly acts as adapter for the autophagy machinery at the outer and ATG8a as cargo receptor at the inner membrane of the autophagosome.
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Affiliation(s)
- Susanne Meßling
- Center for Biochemistry, Institute of Biochemistry I, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Cologne, Germany
| | - Jan Matthias
- Center for Biochemistry, Institute of Biochemistry I, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Cologne, Germany
| | - Qiuhong Xiong
- Center for Biochemistry, Institute of Biochemistry I, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Cologne, Germany
| | - Sarah Fischer
- Center for Biochemistry, Institute of Biochemistry I, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Cologne, Germany
| | - Ludwig Eichinger
- Center for Biochemistry, Institute of Biochemistry I, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Cologne, Germany.
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Martínez-García R, Tarnita CE. Lack of Ecological and Life History Context Can Create the Illusion of Social Interactions in Dictyostelium discoideum. PLoS Comput Biol 2016; 12:e1005246. [PMID: 27977666 PMCID: PMC5157950 DOI: 10.1371/journal.pcbi.1005246] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Accepted: 11/14/2016] [Indexed: 12/13/2022] Open
Abstract
Studies of social microbes often focus on one fitness component (reproductive success within the social complex), with little information about or attention to other stages of the life cycle or the ecological context. This can lead to paradoxical results. The life cycle of the social amoeba Dictyostelium discoideum includes a multicellular stage in which not necessarily clonal amoebae aggregate upon starvation to form a possibly chimeric (genetically heterogeneous) fruiting body made of dead stalk cells and spores. The lab-measured reproductive skew in the spores of chimeras indicates strong social antagonism that should result in low genotypic diversity, which is inconsistent with observations from nature. Two studies have suggested that this inconsistency stems from the one-dimensional assessment of fitness (spore production) and that the solution lies in tradeoffs between multiple life-history traits, e.g.: spore size versus viability; and spore-formation (via aggregation) versus staying vegetative (as non-aggregated cells). We develop an ecologically-grounded, socially-neutral model (i.e. no social interactions between genotypes) for the life cycle of social amoebae in which we theoretically explore multiple non-social life-history traits, tradeoffs and tradeoff-implementing mechanisms. We find that spore production comes at the expense of time to complete aggregation, and, depending on the experimental setup, spore size and viability. Furthermore, experimental results regarding apparent social interactions within chimeric mixes can be qualitatively recapitulated under this neutral hypothesis, without needing to invoke social interactions. This allows for simple potential resolutions to the previously paradoxical results. We conclude that the complexities of life histories, including social behavior and multicellularity, can only be understood in the appropriate multidimensional ecological context, when considering all stages of the life cycle. Fitness in social microbes is often measured in terms of reproductive success in the social stage, with little regard to other stages of the life cycle (e.g. solitary) or to the ecological context. This approach can lead to seemingly paradoxical results that point to complex social interactions (e.g., social cheating) among individuals in the population. However, recent experimental studies in Dictyostelium discoideum, one of the most studied social microbes, have highlighted various tradeoffs among previously ignored non-social traits that should affect fitness. We develop an ecologically-motivated socially-neutral model for the life cycle of D. discoideum that combines these proposed traits and tradeoffs and proposes new ones to determine whether existing observations can be explained without the need to invoke social interactions. We confirm this expectation and conclude that the complexities of social behavior can only be understood in the appropriate ecological context, when considering a complete description of the life cycle.
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Affiliation(s)
- Ricardo Martínez-García
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton NJ, United States of America
| | - Corina E Tarnita
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton NJ, United States of America
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31
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Koller B, Schramm C, Siebert S, Triebel J, Deland E, Pfefferkorn AM, Rickerts V, Thewes S. Dictyostelium discoideum as a Novel Host System to Study the Interaction between Phagocytes and Yeasts. Front Microbiol 2016; 7:1665. [PMID: 27818653 PMCID: PMC5073093 DOI: 10.3389/fmicb.2016.01665] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Accepted: 10/05/2016] [Indexed: 01/26/2023] Open
Abstract
The social amoeba Dictyostelium discoideum is a well-established model organism to study the interaction between bacteria and phagocytes. In contrast, research using D. discoideum as a host model for fungi is rare. We describe a comprehensive study, which uses D. discoideum as a host model system to investigate the interaction with apathogenic (Saccharomyces cerevisiae) and pathogenic (Candida sp.) yeast. We show that Dictyostelium can be co-cultivated with yeasts on solid media, offering a convenient test to study the interaction between fungi and phagocytes. We demonstrate that a number of D. discoideum mutants increase (atg1-, kil1-, kil2-) or decrease (atg6-) the ability of the amoebae to predate yeast cells. On the yeast side, growth characteristics, reduced phagocytosis rate, as well as known virulence factors of C. albicans (EFG1, CPH1, HGC1, ICL1) contribute to the resistance of yeast cells against predation by the amoebae. Investigating haploid C. albicans strains, we suggest using the amoebae plate test for screening purposes after random mutagenesis. Finally, we discuss the potential of our adapted amoebae plate test to use D. discoideum for risk assessment of yeast strains.
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Affiliation(s)
- Barbara Koller
- Department of Biology, Chemistry, Pharmacy, Institute for Biology - Microbiology, Freie Universität Berlin Berlin, Germany
| | - Christin Schramm
- Department of Biology, Chemistry, Pharmacy, Institute for Biology - Microbiology, Freie Universität BerlinBerlin, Germany; FG16, Robert Koch InstituteBerlin, Germany
| | - Susann Siebert
- Department of Biology, Chemistry, Pharmacy, Institute for Biology - Microbiology, Freie Universität Berlin Berlin, Germany
| | - János Triebel
- Department of Biology, Chemistry, Pharmacy, Institute for Biology - Microbiology, Freie Universität Berlin Berlin, Germany
| | - Eric Deland
- Department of Biology, Chemistry, Pharmacy, Institute for Biology - Microbiology, Freie Universität Berlin Berlin, Germany
| | - Anna M Pfefferkorn
- Department of Biology, Chemistry, Pharmacy, Institute for Biology - Microbiology, Freie Universität Berlin Berlin, Germany
| | | | - Sascha Thewes
- Department of Biology, Chemistry, Pharmacy, Institute for Biology - Microbiology, Freie Universität Berlin Berlin, Germany
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Mesquita A, Cardenal-Muñoz E, Dominguez E, Muñoz-Braceras S, Nuñez-Corcuera B, Phillips BA, Tábara LC, Xiong Q, Coria R, Eichinger L, Golstein P, King JS, Soldati T, Vincent O, Escalante R. Autophagy in Dictyostelium: Mechanisms, regulation and disease in a simple biomedical model. Autophagy 2016; 13:24-40. [PMID: 27715405 DOI: 10.1080/15548627.2016.1226737] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Autophagy is a fast-moving field with an enormous impact on human health and disease. Understanding the complexity of the mechanism and regulation of this process often benefits from the use of simple experimental models such as the social amoeba Dictyostelium discoideum. Since the publication of the first review describing the potential of D. discoideum in autophagy, significant advances have been made that demonstrate both the experimental advantages and interest in using this model. Since our previous review, research in D. discoideum has shed light on the mechanisms that regulate autophagosome formation and contributed significantly to the study of autophagy-related pathologies. Here, we review these advances, as well as the current techniques to monitor autophagy in D. discoideum. The comprehensive bioinformatics search of autophagic proteins that was a substantial part of the previous review has not been revisited here except for those aspects that challenged previous predictions such as the composition of the Atg1 complex. In recent years our understanding of, and ability to investigate, autophagy in D. discoideum has evolved significantly and will surely enable and accelerate future research using this model.
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Affiliation(s)
- Ana Mesquita
- a Instituto de Investigaciones Biomédicas "Alberto Sols" (CSIC-UAM) , Madrid , Spain.,b University of Cincinnati College of Medicine , Cincinnati , OH , USA
| | - Elena Cardenal-Muñoz
- c Départment de Biochimie , Faculté des Sciences, Université de Genève , Switzerland
| | - Eunice Dominguez
- a Instituto de Investigaciones Biomédicas "Alberto Sols" (CSIC-UAM) , Madrid , Spain.,d Departamento de Genética Molecular , Instituto de Fisiología Celular, Universidad Nacional Autónoma de México , Mexico City , México
| | - Sandra Muñoz-Braceras
- a Instituto de Investigaciones Biomédicas "Alberto Sols" (CSIC-UAM) , Madrid , Spain
| | | | - Ben A Phillips
- e Department of Biomedical Sciences , University of Sheffield , UK
| | - Luis C Tábara
- a Instituto de Investigaciones Biomédicas "Alberto Sols" (CSIC-UAM) , Madrid , Spain
| | - Qiuhong Xiong
- f Center for Biochemistry, Medical Faculty, University of Cologne , Cologne , Germany
| | - Roberto Coria
- d Departamento de Genética Molecular , Instituto de Fisiología Celular, Universidad Nacional Autónoma de México , Mexico City , México
| | - Ludwig Eichinger
- f Center for Biochemistry, Medical Faculty, University of Cologne , Cologne , Germany
| | - Pierre Golstein
- g Centre d'Immunologie de Marseille-Luminy, Aix Marseille Université UM2 , Inserm, U1104, CNRS UMR7280, Marseille , France
| | - Jason S King
- e Department of Biomedical Sciences , University of Sheffield , UK
| | - Thierry Soldati
- c Départment de Biochimie , Faculté des Sciences, Université de Genève , Switzerland
| | - Olivier Vincent
- a Instituto de Investigaciones Biomédicas "Alberto Sols" (CSIC-UAM) , Madrid , Spain
| | - Ricardo Escalante
- a Instituto de Investigaciones Biomédicas "Alberto Sols" (CSIC-UAM) , Madrid , Spain
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Mesquita A, Tábara LC, Martinez-Costa O, Santos-Rodrigo N, Vincent O, Escalante R. Dissecting the function of Atg1 complex in Dictyostelium autophagy reveals a connection with the pentose phosphate pathway enzyme transketolase. Open Biol 2016; 5:rsob.150088. [PMID: 26246495 PMCID: PMC4554924 DOI: 10.1098/rsob.150088] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The network of protein–protein interactions of the Dictyostelium discoideum autophagy pathway was investigated by yeast two-hybrid screening of the conserved autophagic proteins Atg1 and Atg8. These analyses confirmed expected interactions described in other organisms and also identified novel interactors that highlight the complexity of autophagy regulation. The Atg1 kinase complex, an essential regulator of autophagy, was investigated in detail here. The composition of the Atg1 complex in D. discoideum is more similar to mammalian cells than to Saccharomyces cerevisiae as, besides Atg13, it contains Atg101, a protein not conserved in this yeast. We found that Atg101 interacts with Atg13 and genetic disruption of these proteins in Dictyostelium leads to an early block in autophagy, although the severity of the developmental phenotype and the degree of autophagic block is higher in Atg13-deficient cells. We have also identified a protein containing zinc-finger B-box and FNIP motifs that interacts with Atg101. Disruption of this protein increases autophagic flux, suggesting that it functions as a negative regulator of Atg101. We also describe the interaction of Atg1 kinase with the pentose phosphate pathway enzyme transketolase (TKT). We found changes in the activity of endogenous TKT activity in strains lacking or overexpressing Atg1, suggesting the presence of an unsuspected regulatory pathway between autophagy and the pentose phosphate pathway in Dictyostelium that seems to be conserved in mammalian cells.
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Affiliation(s)
- Ana Mesquita
- Instituto de Investigaciones Biomédicas Alberto Sols, CSIC/UAM, Madrid, Spain
| | - Luis C Tábara
- Instituto de Investigaciones Biomédicas Alberto Sols, CSIC/UAM, Madrid, Spain
| | | | | | - Olivier Vincent
- Instituto de Investigaciones Biomédicas Alberto Sols, CSIC/UAM, Madrid, Spain
| | - Ricardo Escalante
- Instituto de Investigaciones Biomédicas Alberto Sols, CSIC/UAM, Madrid, Spain
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Xiong Q, Ünal C, Matthias J, Steinert M, Eichinger L. The phenotypes of ATG9, ATG16 and ATG9/16 knock-out mutants imply autophagy-dependent and -independent functions. Open Biol 2016; 5:150008. [PMID: 25878144 PMCID: PMC4422124 DOI: 10.1098/rsob.150008] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Macroautophagy is a highly conserved intracellular bulk degradation system of all eukaryotic cells. It is governed by a large number of autophagy proteins (ATGs) and is crucial for many cellular processes. Here, we describe the phenotypes of Dictyostelium discoideum ATG16(-) and ATG9(-)/16(-) cells and compare them to the previously reported ATG9(-) mutant. ATG16 deficiency caused an increase in the expression of several core autophagy genes, among them atg9 and the two atg8 paralogues. The single and double ATG9 and ATG16 knock-out mutants had complex phenotypes and displayed severe and comparable defects in pinocytosis and phagocytosis. Uptake of Legionella pneumophila was reduced. In addition, ATG9(-) and ATG16(-) cells had dramatic defects in autophagy, development and proteasomal activity which were much more severe in the ATG9(-)/16(-) double mutant. Mutant cells showed an increase in poly-ubiquitinated proteins and contained large ubiquitin-positive protein aggregates which partially co-localized with ATG16-GFP in ATG9(-)/16(-) cells. The more severe autophagic, developmental and proteasomal phenotypes of ATG9(-)/16(-) cells imply that ATG9 and ATG16 probably function in parallel in autophagy and have in addition autophagy-independent functions in further cellular processes.
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Affiliation(s)
- Qiuhong Xiong
- Zentrum für Biochemie, Medizinische Fakultät, Universität zu Köln, Joseph-Stelzmann-Strasse 52, Köln 50931, Germany
| | - Can Ünal
- Institut für Mikrobiologie, Technische Universität Braunschweig, Spielmannstrasse 7, Braunschweig 38106, Germany Fen Fakültesi, Türk-Alman-Üniversitesi, Istanbul 34820, Turkey
| | - Jan Matthias
- Zentrum für Biochemie, Medizinische Fakultät, Universität zu Köln, Joseph-Stelzmann-Strasse 52, Köln 50931, Germany
| | - Michael Steinert
- Institut für Mikrobiologie, Technische Universität Braunschweig, Spielmannstrasse 7, Braunschweig 38106, Germany Helmholtz Centre for Infection Research, Braunschweig 38124, Germany
| | - Ludwig Eichinger
- Zentrum für Biochemie, Medizinische Fakultät, Universität zu Köln, Joseph-Stelzmann-Strasse 52, Köln 50931, Germany
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The two Dictyostelium autophagy eight proteins, ATG8a and ATG8b, associate with the autophagosome in succession. Eur J Cell Biol 2016; 95:15-25. [DOI: 10.1016/j.ejcb.2015.10.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Revised: 10/27/2015] [Accepted: 10/29/2015] [Indexed: 12/19/2022] Open
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Dissection of Francisella-Host Cell Interactions in Dictyostelium discoideum. Appl Environ Microbiol 2015; 82:1586-1598. [PMID: 26712555 DOI: 10.1128/aem.02950-15] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Accepted: 12/22/2015] [Indexed: 12/31/2022] Open
Abstract
Francisella bacteria cause severe disease in both vertebrates and invertebrates and include one of the most infectious human pathogens. Mammalian cell lines have mainly been used to study the mechanisms by which Francisella manipulates its host to replicate within a large variety of hosts and cell types, including macrophages. Here, we describe the establishment of a genetically and biochemically tractable infection model: the amoeba Dictyostelium discoideum combined with the fish pathogen Francisella noatunensis subsp. noatunensis. Phagocytosed F. noatunensis subsp. noatunensis interacts with the endosomal pathway and escapes further phagosomal maturation by translocating into the host cell cytosol. F. noatunensis subsp. noatunensis lacking IglC, a known virulence determinant required for Francisella intracellular replication, follows the normal phagosomal maturation and does not grow in Dictyostelium. The attenuation of the F. noatunensis subsp. noatunensis ΔiglC mutant was confirmed in a zebrafish embryo model, where growth of F. noatunensis subsp. noatunensis ΔiglC was restricted. In Dictyostelium, F. noatunensis subsp. noatunensis interacts with the autophagic machinery. The intracellular bacteria colocalize with autophagic markers, and when autophagy is impaired (Dictyostelium Δatg1), F. noatunensis subsp. noatunensis accumulates within Dictyostelium cells. Altogether, the Dictyostelium-F. noatunensis subsp. noatunensis infection model recapitulates the course of infection described in other host systems. The genetic and biochemical tractability of the system allows new approaches to elucidate the dynamic interactions between pathogenic Francisella and its host organism.
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Loomis WF. Genetic control of morphogenesis in Dictyostelium. Dev Biol 2015; 402:146-61. [PMID: 25872182 PMCID: PMC4464777 DOI: 10.1016/j.ydbio.2015.03.016] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Revised: 03/12/2015] [Accepted: 03/25/2015] [Indexed: 01/06/2023]
Abstract
Cells grow, move, expand, shrink and die in the process of generating the characteristic shapes of organisms. Although the structures generated during development of the social amoeba Dictyostelium discoideum look nothing like the structures seen in metazoan embryogenesis, some of the morphogenetic processes used in their making are surprisingly similar. Recent advances in understanding the molecular basis for directed cell migration, cell type specific sorting, differential adhesion, secretion of matrix components, pattern formation, regulation and terminal differentiation are reviewed. Genes involved in Dictyostelium aggregation, slug formation, and culmination of fruiting bodies are discussed.
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Affiliation(s)
- William F Loomis
- Cell and Developmental Biology, Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093, United States.
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Muñoz-Braceras S, Calvo R, Escalante R. TipC and the chorea-acanthocytosis protein VPS13A regulate autophagy inDictyosteliumand human HeLa cells. Autophagy 2015; 11:918-27. [DOI: 10.1080/15548627.2015.1034413] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
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Autophagy inhibitors as a potential antiamoebic treatment for Acanthamoeba keratitis. Antimicrob Agents Chemother 2015; 59:4020-5. [PMID: 25896709 DOI: 10.1128/aac.05165-14] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2014] [Accepted: 04/16/2015] [Indexed: 02/06/2023] Open
Abstract
Acanthamoeba cysts are resistant to extreme physical and chemical conditions. Autophagy is an essential pathway for encystation of Acanthamoeba cells. To evaluate the possibility of an autophagic Acanthamoeba encystation mechanism, we evaluated autophagy inhibitors, such as 3-methyladenine (3MA), LY294002, wortmannin, bafilomycin A, and chloroquine. Among these autophagy inhibitors, the use of 3MA and chloroquine showed a significant reduction in the encystation ratio in Acanthamoeba cells. Wortmannin also inhibited the formation of mature cysts, while LY294002 and bafilomycin A did not affect the encystation of Acanthamoeba cells. Transmission electron microscopy revealed that 3MA and wortmannin inhibited autophagy formation and that chloroquine interfered with the formation of autolysosomes. Inhibition of autophagy or autolysosome formation resulted in a significant block in the encystation in Acanthamoeba cells. Clinical treatment with 0.02% polyhexamethylene biguanide (PHMB) showed high cytopathic effects on Acanthamoeba trophozoites and cysts; however, it also revealed high cytopathic effects on human corneal epithelial cells. In this study, we investigated effects of the combination of a low (0.00125%) concentration of PHMB with each of the autophagy inhibitors 3MA, wortmannin, and chloroquine on Acanthamoeba and human corneal epithelial cells. These new combination treatments showed low cytopathic effects on human corneal cells and high cytopathic effects on Acanthamoeba cells. Taken together, these results provide fundamental information for optimizing the treatment of Acanthamoeba keratitis.
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Abstract
In contrast to mechanisms mediating uptake of intracellular bacterial pathogens, bacterial egress and cell-to-cell transmission are poorly understood. Previously, we showed that the transmission of pathogenic mycobacteria between phagocytic cells also depends on nonlytic ejection through an F-actin based structure, called the ejectosome. How the host cell maintains integrity of its plasma membrane during the ejection process was unknown. Here, we reveal an unexpected function for the autophagic machinery in nonlytic spreading of bacteria. We show that ejecting mycobacteria are escorted by a distinct polar autophagocytic vacuole. If autophagy is impaired, cell-to-cell transmission is inhibited, the host plasma membrane becomes compromised and the host cells die. These findings highlight a previously unidentified, highly ordered interaction between bacteria and the autophagic pathway and might represent the ancient way to ensure nonlytic egress of bacteria.
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Fouque E, Yefimova M, Trouilhé MC, Quellard N, Fernandez B, Rodier MH, Thomas V, Humeau P, Héchard Y. Morphological Study of the Encystment and Excystment of Vermamoeba vermiformis
Revealed Original Traits. J Eukaryot Microbiol 2014; 62:327-37. [DOI: 10.1111/jeu.12185] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Revised: 08/19/2014] [Accepted: 08/25/2014] [Indexed: 11/30/2022]
Affiliation(s)
- Emilie Fouque
- Université de Poitiers; UMR CNRS 7267; Ecologie et Biologie des Interactions (EBI); 1 rue G. Bonnet 86073 Poitiers Cedex France
- Sechenov Institute of Evolutionary Physiology and Biochemistry; Russian Academy of Sciences; 194223 Saint-Petersburg Russia
| | - Marina Yefimova
- Université de Poitiers; ERL 7368 CNRS; Signalisation et Transports Ioniques Membranaires (STIM); 1 rue G. Bonnet 86073 Poitiers Cedex France
- Sechenov Institute of Evolutionary Physiology and Biochemistry; Russian Academy of Sciences; 194223 Saint-Petersburg Russia
| | - Marie-Cécile Trouilhé
- Scientific and Technical Center for Building; AQUASIM; 11 rue Henri Picherit BP 82341 44323 Nantes Cedex 3 France
| | - Nathalie Quellard
- Université de Poitiers; Service d'Anatomie et Cytologie Pathologiques; CHU de Poitiers; 2 rue de la Milétrie 86000 Poitiers France
| | - Béatrice Fernandez
- Université de Poitiers; Service d'Anatomie et Cytologie Pathologiques; CHU de Poitiers; 2 rue de la Milétrie 86000 Poitiers France
| | - Marie-Hélène Rodier
- Université de Poitiers; UMR CNRS 7267; Ecologie et Biologie des Interactions (EBI); 1 rue G. Bonnet 86073 Poitiers Cedex France
| | | | - Philippe Humeau
- Scientific and Technical Center for Building; AQUASIM; 11 rue Henri Picherit BP 82341 44323 Nantes Cedex 3 France
| | - Yann Héchard
- Université de Poitiers; UMR CNRS 7267; Ecologie et Biologie des Interactions (EBI); 1 rue G. Bonnet 86073 Poitiers Cedex France
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Calvo-Garrido J, King JS, Muñoz-Braceras S, Escalante R. Vmp1 regulates PtdIns3P signaling during autophagosome formation in Dictyostelium discoideum. Traffic 2014; 15:1235-46. [PMID: 25131297 DOI: 10.1111/tra.12210] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Revised: 08/13/2014] [Accepted: 08/13/2014] [Indexed: 01/08/2023]
Abstract
Generation and turnover of phosphatidylinositol 3-phosphate (PtdIns3P) signaling is essential for autophagosome formation and other membrane traffic processes. In both Dictyostelium discoideum and mammalian cells, autophagosomes are formed from specialized regions of the endoplasmic reticulum (ER), called omegasomes, which are enriched in the signaling lipid PtdIns3P. Vacuole membrane protein 1 (Vmp1) is a multispanning membrane protein localized at the ER that is required for autophagosome formation. There are conflicting reports in the literature as to whether Vmp1 is strictly required or not for autophagy-related PtdIns3P signaling and its hierarchical relationship with Atg1 and PI3K. We have now addressed these questions in the Dictyostelium model. We show that Dictyostelium cells lacking Vmp1 have elevated and aberrant PtdIns3P signaling on the ER, resulting in an increased and persistent recruitment of Atg18 and other autophagic proteins. This indicates that Vmp1 is not strictly essential for the generation of PtdIns3P signaling but rather suggests a role in the correct turnover or modulation of this signaling. Of interest, these PtdIns3P-enriched regions of the ER surround ubiquitinated protein aggregates but are unable to form functional autophagosomes. vmp1 null cells also have additional defects in macropinocytosis and growth, which are not shared by other autophagy mutants. Remarkably, we show that these defects and also the aberrant PtdIns3P distribution are largely suppressed by the concomitant loss of Atg1, indicating that aberrant autophagic signaling on the ER inhibits macropinocytosis. These results suggest that Atg1 functions upstream of Vmp1 in this signaling pathway and demonstrates a previously unappreciated link between abnormal autophagy signaling and macropinocytosis.
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Affiliation(s)
- Javier Calvo-Garrido
- Instituto de Investigaciones Biomédicas Alberto Sols, C.S.I.C./U.A.M., Madrid, 28029, Spain
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Dubravcic D, van Baalen M, Nizak C. An evolutionarily significant unicellular strategy in response to starvation in Dictyostelium social amoebae. F1000Res 2014; 3:133. [PMID: 25309731 PMCID: PMC4184345 DOI: 10.12688/f1000research.4218.1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 12/01/2014] [Indexed: 02/04/2024] Open
Abstract
The social amoeba Dictyostelium discoideum is widely studied for its multicellular development program as a response to starvation. Aggregates of up to 10 (6) cells form fruiting bodies containing (i) dormant spores (~80%) that can persist for months in the absence of nutrients, and (ii) dead stalk cells (~20%) that promote the dispersion of the spores towards nutrient-rich areas. It is often overlooked that not all cells aggregate upon starvation. Using a new quantitative approach based on time-lapse fluorescence microscopy and a low ratio of reporting cells, we have quantified this fraction of non-aggregating cells. In realistic starvation conditions, up to 15% of cells do not aggregate, which makes this third cell fate a significant component of the population-level response of social amoebae to starvation. Non-aggregating cells have an advantage over cells in aggregates since they resume growth earlier upon arrival of new nutrients, but have a shorter lifespan under prolonged starvation. We find that phenotypic heterogeneities linked to cell nutritional state bias the representation of cells in the aggregating vs. non-aggregating fractions, and thus affect population partitioning. Next, we report that the fraction of non-aggregating cells depends on genetic factors that regulate the timing of starvation, signal sensing efficiency and aggregation efficiency. In addition, interactions between clones in mixtures of non-isogenic cells affect the partitioning of each clone into both fractions. We further build a numerical model to test the evolutionary significance of the non-aggregating cell fraction. The partitioning of cells into aggregating and non-aggregating fractions is optimal in fluctuating environments with an unpredictable duration of starvation periods. Our study highlights the unicellular component of the response of social amoebae to starvation, and thus extends its evolutionary and ecological framework.
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Affiliation(s)
- Darja Dubravcic
- CNRS, LIPHY, F-38000 Grenoble, France
- Laboratory of Ecology and Evolution, CNRS UMR7625, Ecole Normale Supérieure, Université Pierre et Marie Curie, Paris Universitas, CNRS, Paris, France
| | - Minus van Baalen
- Laboratory of Ecology and Evolution, CNRS UMR7625, Ecole Normale Supérieure, Université Pierre et Marie Curie, Paris Universitas, CNRS, Paris, France
| | - Clément Nizak
- CNRS, LIPHY, F-38000 Grenoble, France
- Laboratory of Biochemistry, UMR 8231 ESPCI ParisTech/CNRS, PSL Research University, Paris, France
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44
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Dubravcic D, van Baalen M, Nizak C. An evolutionarily significant unicellular strategy in response to starvation in Dictyostelium social amoebae. F1000Res 2014; 3:133. [PMID: 25309731 PMCID: PMC4184345 DOI: 10.12688/f1000research.4218.2] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 12/01/2014] [Indexed: 11/20/2022] Open
Abstract
The social amoeba Dictyostelium discoideum is widely studied for its multicellular development program as a response to starvation. Aggregates of up to 10 (6) cells form fruiting bodies containing (i) dormant spores (~80%) that can persist for months in the absence of nutrients, and (ii) dead stalk cells (~20%) that promote the dispersion of the spores towards nutrient-rich areas. It is often overlooked that not all cells aggregate upon starvation. Using a new quantitative approach based on time-lapse fluorescence microscopy and a low ratio of reporting cells, we have quantified this fraction of non-aggregating cells. In realistic starvation conditions, up to 15% of cells do not aggregate, which makes this third cell fate a significant component of the population-level response of social amoebae to starvation. Non-aggregating cells have an advantage over cells in aggregates since they resume growth earlier upon arrival of new nutrients, but have a shorter lifespan under prolonged starvation. We find that phenotypic heterogeneities linked to cell nutritional state bias the representation of cells in the aggregating vs. non-aggregating fractions, and thus affect population partitioning. Next, we report that the fraction of non-aggregating cells depends on genetic factors that regulate the timing of starvation, signal sensing efficiency and aggregation efficiency. In addition, interactions between clones in mixtures of non-isogenic cells affect the partitioning of each clone into both fractions. We further build a numerical model to test the evolutionary significance of the non-aggregating cell fraction. The partitioning of cells into aggregating and non-aggregating fractions is optimal in fluctuating environments with an unpredictable duration of starvation periods. Our study highlights the unicellular component of the response of social amoebae to starvation, and thus extends its evolutionary and ecological framework.
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Affiliation(s)
- Darja Dubravcic
- CNRS, LIPHY, F-38000 Grenoble, France ; Laboratory of Ecology and Evolution, CNRS UMR7625, Ecole Normale Supérieure, Université Pierre et Marie Curie, Paris Universitas, CNRS, Paris, France
| | - Minus van Baalen
- Laboratory of Ecology and Evolution, CNRS UMR7625, Ecole Normale Supérieure, Université Pierre et Marie Curie, Paris Universitas, CNRS, Paris, France
| | - Clément Nizak
- CNRS, LIPHY, F-38000 Grenoble, France ; Laboratory of Biochemistry, UMR 8231 ESPCI ParisTech/CNRS, PSL Research University, Paris, France
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Annesley SJ, Chen S, Francione LM, Sanislav O, Chavan AJ, Farah C, De Piazza SW, Storey CL, Ilievska J, Fernando SG, Smith PK, Lay ST, Fisher PR. Dictyostelium, a microbial model for brain disease. Biochim Biophys Acta Gen Subj 2013; 1840:1413-32. [PMID: 24161926 DOI: 10.1016/j.bbagen.2013.10.019] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Revised: 10/05/2013] [Accepted: 10/10/2013] [Indexed: 12/25/2022]
Abstract
BACKGROUND Most neurodegenerative diseases are associated with mitochondrial dysfunction. In humans, mutations in mitochondrial genes result in a range of phenotypic outcomes which do not correlate well with the underlying genetic cause. Other neurodegenerative diseases are caused by mutations that affect the function and trafficking of lysosomes, endosomes and autophagosomes. Many of the complexities of these human diseases can be avoided by studying them in the simple eukaryotic model Dictyostelium discoideum. SCOPE OF REVIEW This review describes research using Dictyostelium to study cytopathological pathways underlying a variety of neurodegenerative diseases including mitochondrial, lysosomal and vesicle trafficking disorders. MAJOR CONCLUSIONS Generalised mitochondrial respiratory deficiencies in Dictyostelium produce a consistent pattern of defective phenotypes that are caused by chronic activation of a cellular energy sensor AMPK (AMP-activated protein kinase) and not ATP deficiency per se. Surprisingly, when individual subunits of Complex I are knocked out, both AMPK-dependent and AMPK-independent, subunit-specific phenotypes are observed. Many nonmitochondrial proteins associated with neurological disorders have homologues in Dictyostelium and are associated with the function and trafficking of lysosomes and endosomes. Conversely, some genes associated with neurodegenerative disorders do not have homologues in Dictyostelium and this provides a unique avenue for studying these mutated proteins in the absence of endogeneous protein. GENERAL SIGNIFICANCE Using the Dictyostelium model we have gained insights into the sublethal cytopathological pathways whose dysregulation contributes to phenotypic outcomes in neurodegenerative disease. This work is beginning to distinguish correlation, cause and effect in the complex network of cross talk between the various organelles involved. This article is part of a Special Issue entitled Frontiers of Mitochondrial Research.
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Affiliation(s)
- S J Annesley
- Department of Microbiology, La Trobe University, Plenty Rd., Bundoora, VIC, Australia, 3086
| | - S Chen
- Department of Microbiology, La Trobe University, Plenty Rd., Bundoora, VIC, Australia, 3086
| | - L M Francione
- Department of Microbiology, La Trobe University, Plenty Rd., Bundoora, VIC, Australia, 3086
| | - O Sanislav
- Department of Microbiology, La Trobe University, Plenty Rd., Bundoora, VIC, Australia, 3086
| | - A J Chavan
- Department of Microbiology, La Trobe University, Plenty Rd., Bundoora, VIC, Australia, 3086
| | - C Farah
- Department of Microbiology, La Trobe University, Plenty Rd., Bundoora, VIC, Australia, 3086
| | - S W De Piazza
- Department of Microbiology, La Trobe University, Plenty Rd., Bundoora, VIC, Australia, 3086
| | - C L Storey
- Department of Microbiology, La Trobe University, Plenty Rd., Bundoora, VIC, Australia, 3086
| | - J Ilievska
- Department of Microbiology, La Trobe University, Plenty Rd., Bundoora, VIC, Australia, 3086
| | - S G Fernando
- Department of Microbiology, La Trobe University, Plenty Rd., Bundoora, VIC, Australia, 3086
| | - P K Smith
- Department of Microbiology, La Trobe University, Plenty Rd., Bundoora, VIC, Australia, 3086
| | - S T Lay
- Department of Microbiology, La Trobe University, Plenty Rd., Bundoora, VIC, Australia, 3086
| | - P R Fisher
- Department of Microbiology, La Trobe University, Plenty Rd., Bundoora, VIC, Australia, 3086.
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Rodríguez-Ruiz A, Marigómez I, Boatti L, Viarengo A. Dictyostelium discoideum developmental cycle (DDDC) assay: a tool for Hg toxicity assessment and soil health screening. THE SCIENCE OF THE TOTAL ENVIRONMENT 2013; 450-451:39-50. [PMID: 23454908 DOI: 10.1016/j.scitotenv.2013.01.060] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2012] [Revised: 01/19/2013] [Accepted: 01/19/2013] [Indexed: 06/01/2023]
Abstract
The social amoeba Dictyostelium discoideum has been proposed for assessing stress responses to pollutants in soil and it has already been successfully employed in the aquatic environment. Presently, we developed the DDDC assay (D. discoideum developmental cycle assay) for both soil toxicity assessment and soil health screening. The DDDC assay is primarily aimed at determining the capacity of D. discoideum to undergo its developmental programme forming a fruiting body, measured in terms of fruiting body formation inhibition and fruiting body size factor, which may be considered an indication of its ecological fitness (potential for spore dispersal). A second objective of the solid phase DDDC assay is to identify potential mechanisms of toxic action on the developmental cycle, for which three checkpoints are examined: (a) aggregation arrest, (b) migration arrest, and (c) culmination arrest. Presently, conditions for the DDDC assay such as soil texture, soil water content, soil pH, food availability and incubation time were investigated and optimized. In addition, both solid and liquid phase variants of the DDDC assay were applied to assess the toxicity of Hg, at regulatory concentrations. The developmental cycle and ecological fitness were affected from the exposure to 0.3 mg Hg/kg dry-wt soil onwards. The DDDC assay has been shown to be a high sensitivity test.
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Affiliation(s)
- Amaia Rodríguez-Ruiz
- Ekoiz-Berrilur Consortium, CBET Res. Grp. Zoology & Animal Cell Biology Dept., Science & Technol. Fac., University of the Basque Country (UPV/EHU), Sarriena 48940 Leioa-Bizkaia, Basque Country, Spain
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Arhzaouy K, Strucksberg KH, Tung SM, Tangavelou K, Stumpf M, Faix J, Schröder R, Clemen CS, Eichinger L. Heteromeric p97/p97R155C complexes induce dominant negative changes in wild-type and autophagy 9-deficient Dictyostelium strains. PLoS One 2012; 7:e46879. [PMID: 23056506 PMCID: PMC3463532 DOI: 10.1371/journal.pone.0046879] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Accepted: 09/06/2012] [Indexed: 11/19/2022] Open
Abstract
Heterozygous mutations in the human VCP (p97) gene cause autosomal-dominant IBMPFD (inclusion body myopathy with early onset Paget's disease of bone and frontotemporal dementia), ALS14 (amyotrophic lateral sclerosis with or without frontotemporal dementia) and HSP (hereditary spastic paraplegia). Most prevalent is the R155C point mutation. We studied the function of p97 in the social amoeba Dictyostelium discoideum and have generated strains that ectopically express wild-type (p97) or mutant p97 (p97(R155C)) fused to RFP in AX2 wild-type and autophagy 9 knock-out (ATG9(KO)) cells. Native gel electrophoresis showed that both p97 and p97(R155C) assemble into hexamers. Co-immunoprecipitation studies revealed that endogenous p97 and p97(R155C)-RFP form heteromers. The mutant strains displayed changes in cell growth, phototaxis, development, proteasomal activity, ubiquitinylated proteins, and ATG8(LC3) indicating mis-regulation of multiple essential cellular processes. Additionally, immunofluorescence analysis revealed an increase of protein aggregates in ATG9(KO)/p97(R155C)-RFP and ATG9(KO) cells. They were positive for ubiquitin in both strains, however, solely immunoreactive for p97 in the ATG9(KO) mutant. A major finding is that the expression of p97(R155C)-RFP in the ATG9(KO) strain partially or fully rescued the pleiotropic phenotype. We also observed dose-dependent effects of p97 on several cellular processes. Based on findings in the single versus the double mutants we propose a novel mode of p97 interaction with the core autophagy protein ATG9 which is based on mutual inhibition.
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Affiliation(s)
- Khalid Arhzaouy
- Intitute for Biochemistry I, Medical Faculty, University of Cologne, Cologne, Germany
| | - Karl-Heinz Strucksberg
- Intitute for Biochemistry I, Medical Faculty, University of Cologne, Cologne, Germany
- Institute of Neuropathology, University Hospital Erlangen, Erlangen, Germany
| | - Sze Man Tung
- Intitute for Biochemistry I, Medical Faculty, University of Cologne, Cologne, Germany
| | | | - Maria Stumpf
- Intitute for Biochemistry I, Medical Faculty, University of Cologne, Cologne, Germany
| | - Jan Faix
- Institute for Biophysical Chemistry, Hannover Medical School, Hannover, Germany
| | - Rolf Schröder
- Institute of Neuropathology, University Hospital Erlangen, Erlangen, Germany
| | - Christoph S. Clemen
- Intitute for Biochemistry I, Medical Faculty, University of Cologne, Cologne, Germany
| | - Ludwig Eichinger
- Intitute for Biochemistry I, Medical Faculty, University of Cologne, Cologne, Germany
- * E-mail:
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Abstract
The ability to respond and adapt to changes in the physical environment is a universal and essential cellular property. Here we demonstrated that cells respond to mechanical compressive stress by rapidly inducing autophagosome formation. We measured this response in both Dictyostelium and mammalian cells, indicating that this is an evolutionarily conserved, general response to mechanical stress. In Dictyostelium, the number of autophagosomes increased 20-fold within 10 min of 1 kPa pressure being applied and a similar response was seen in mammalian cells after 30 min. We showed in both cell types that autophagy is highly sensitive to changes in mechanical pressure and the response is graduated, with half-maximal responses at ~0.2 kPa, similar to other mechano-sensitive responses. We further showed that the mechanical induction of autophagy is TOR-independent and transient, lasting until the cells adapt to their new environment and recover their shape. The autophagic response is therefore part of an integrated response to mechanical challenge, allowing cells to cope with a continuously changing physical environment.
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Affiliation(s)
- Jason S King
- Beatson Institute for Cancer Research, Glasgow, Scotland, UK.
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Lipopolysaccharide induction of autophagy is associated with enhanced bactericidal activity in Dictyostelium discoideum. Biochem Biophys Res Commun 2012; 422:417-22. [PMID: 22575510 DOI: 10.1016/j.bbrc.2012.05.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Accepted: 05/01/2012] [Indexed: 11/21/2022]
Abstract
Innate immune cells respond to microbial invaders using pattern recognition receptors that detect conserved microbial patterns. Among the cellular processes stimulated downstream of pattern recognition machinery is the initiation of autophagy, which plays protective roles against intracellular microbes. We have shown recently that Dictyostelium discoideum, which takes up bacteria for nutritive purposes, may employ pattern recognition machinery to respond to bacterial prey, as D. discoideum cells upregulate bactericidal activity upon stimulation by lipopolysaccharide (LPS). Here we extend these findings, showing that LPS treatment leads to induction of autophagosomal maturation in cells responding to the bacteria Staphylococcus aureus. Cells treated with the autophagy-inducing drug rapamycin clear internalized bacteria at an accelerated rate, while LPS-enhanced clearance of bacteria is reduced in cells deficient for the autophagy-related genes atg1 and atg9. These findings link microbial pattern recognition with autophagy in the social amoeba D. discoideum.
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50
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Role of ATG8 and autophagy in programmed nuclear degradation in Tetrahymena thermophila. EUKARYOTIC CELL 2012; 11:494-506. [PMID: 22366125 DOI: 10.1128/ec.05296-11] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Autophagy is an evolutionarily conserved mechanism for the degradation of cellular components, but its role in enucleation during differentiation has not been established. Tetrahymena thermophila is a unicellular eukaryote with two functionally distinct nuclei, the somatic (macro-) and the germ line (micro-) nuclei. These nuclei are produced during sexual reproduction (conjugation), which involves differentiation and selective degradation of several specific nuclei. To examine the role of autophagy in nuclear degradation, we studied the function of two ATG8 genes in Tetrahymena. Through fluorescent protein tagging, we found that both proteins are targeted to degrading nuclei at specific stages, with some enrichment on the nuclear periphery, suggesting the formation of autophagosomes surrounding these nuclei. In addition, ATG8 knockout mutant cells showed a pronounced delay in nuclear degradation without apparently preventing the completion of other developmental events. This evidence provided direct support for a critical role for autophagy in programmed nuclear degradation. The results also showed differential roles for two ATG8 genes, with ATG8-65 playing a more significant role in starvation than ATG8-2, although both are important in nuclear degradation.
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