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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] [MESH Headings] [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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2
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Voss L, Foster OK, Harper L, Morris C, Lavoy S, Brandt JN, Peloza K, Handa S, Maxfield A, Harp M, King B, Eichten V, Rambo FM, Hermann GJ. An ABCG Transporter Functions in Rab Localization and Lysosome-Related Organelle Biogenesis in Caenorhabditis elegans. Genetics 2020; 214:419-445. [PMID: 31848222 PMCID: PMC7017009 DOI: 10.1534/genetics.119.302900] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Accepted: 12/11/2019] [Indexed: 12/20/2022] Open
Abstract
ABC transporters couple ATP hydrolysis to the transport of substrates across cellular membranes. This protein superfamily has diverse activities resulting from differences in their cargo and subcellular localization. Our work investigates the role of the ABCG family member WHT-2 in the biogenesis of gut granules, a Caenorhabditis elegans lysosome-related organelle. In addition to being required for the accumulation of birefringent material within gut granules, WHT-2 is necessary for the localization of gut granule proteins when trafficking pathways to this organelle are partially disrupted. The role of WHT-2 in gut granule protein targeting is likely linked to its function in Rab GTPase localization. We show that WHT-2 promotes the gut granule association of the Rab32 family member GLO-1 and the endolysosomal RAB-7, identifying a novel function for an ABC transporter. WHT-2 localizes to gut granules where it could play a direct role in controlling Rab localization. Loss of CCZ-1 and GLO-3, which likely function as a guanine nucleotide exchange factor (GEF) for GLO-1, lead to similar disruption of GLO-1 localization. We show that CCZ-1, like GLO-3, is localized to gut granules. WHT-2 does not direct the gut granule association of the GLO-1 GEF and our results point to WHT-2 functioning differently than GLO-3 and CCZ-1 Point mutations in WHT-2 that inhibit its transport activity, but not its subcellular localization, lead to the loss of GLO-1 from gut granules, while other WHT-2 activities are not completely disrupted, suggesting that WHT-2 functions in organelle biogenesis through transport-dependent and transport-independent activities.
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Affiliation(s)
- Laura Voss
- Department of Biology, Lewis & Clark College, Portland, Oregon
| | - Olivia K Foster
- Department of Biology, Lewis & Clark College, Portland, Oregon
| | - Logan Harper
- Department of Biology, Lewis & Clark College, Portland, Oregon
| | - Caitlin Morris
- Department of Biology, Lewis & Clark College, Portland, Oregon
| | - Sierra Lavoy
- Department of Biology, Lewis & Clark College, Portland, Oregon
| | - James N Brandt
- Department of Biology, Lewis & Clark College, Portland, Oregon
| | - Kimberly Peloza
- Department of Biology, Lewis & Clark College, Portland, Oregon
| | - Simran Handa
- Department of Biology, Lewis & Clark College, Portland, Oregon
| | - Amanda Maxfield
- Department of Biology, Lewis & Clark College, Portland, Oregon
| | - Marie Harp
- Department of Biology, Lewis & Clark College, Portland, Oregon
| | - Brian King
- Department of Biology, Lewis & Clark College, Portland, Oregon
| | | | - Fiona M Rambo
- Department of Biology, Lewis & Clark College, Portland, Oregon
| | - Greg J Hermann
- Department of Biology, Lewis & Clark College, Portland, Oregon
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3
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Lorkowski SW, Brubaker G, Gulshan K, Smith JD. V-ATPase (Vacuolar ATPase) Activity Required for ABCA1 (ATP-Binding Cassette Protein A1)-Mediated Cholesterol Efflux. Arterioscler Thromb Vasc Biol 2019; 38:2615-2625. [PMID: 30354238 DOI: 10.1161/atvbaha.118.311814] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Objective- We have shown that ABCA1 (ATP-binding cassette protein A1) mediates unfolding of the apoA1 (apolipoprotein A1) N-terminal helical hairpin during apoA1 lipidation. Others have shown that an acidic pH exposes the hydrophobic surface of apoA1. We postulated that the V-ATPase (vacuolar ATPase) proton pump facilitates apoA1 unfolding and promotes ABCA1-mediated cholesterol efflux. Approach and Results- We found that V-ATPase inhibitors dose-dependently decreased ABCA1-mediated cholesterol efflux to apoA1 in baby hamster kidney cells and RAW264.7 cells; and similarly, siRNA knockdown of ATP6V0C inhibited ABCA1-mediated cholesterol efflux to apoA1 in RAW264.7 cells. Although ABCA1 expression did not alter total cellular levels of V-ATPase, ABCA1 increased the cell surface levels of the V0A1 and V1E1 subunits of V-ATPase. We generated a fluorescein isothiocyanate/Alexa647 double-labeled fluorescent ratiometric apoA1 pH indicator whose fluorescein isothiocyanate/Alexa647 emission ratio decreased as the pH drops. We found that ABCA1 induction in baby hamster kidney cells led to acidification of the cell-associated apoA1 pH indicator, compared with control cells without ABCA1 expression. The V-ATPase inhibitor bafilomycin A1 dose-dependently inhibited the apoA1 pH shift in ABCA1-expressing cells, without affecting the levels of cell-associated apoA1. However, we were not able to detect ABCA1-mediated extracellular proton release. We showed that acidic pH facilitated apoA1 unfolding, apoA1 solubilization of phosphatidycholine:phosphatidyserine liposomes, and increased lipid fluidity of these liposomes. Conclusions- Our results support a model that ABCA1 recruits V-ATPase to the plasma membrane where V-ATPase mediates apoA1 acidification and membrane remodeling that promote apoA1 unfolding and ABCA1-mediated HDL (high-density lipoprotein) biogenesis and lipid efflux.
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Affiliation(s)
- Shuhui Wang Lorkowski
- From the Department of Cellular and Molecular Medicine (S.W.L., G.B., K.G., J.D.S.), Cleveland Clinic, OH
| | - Gregory Brubaker
- From the Department of Cellular and Molecular Medicine (S.W.L., G.B., K.G., J.D.S.), Cleveland Clinic, OH
| | - Kailash Gulshan
- From the Department of Cellular and Molecular Medicine (S.W.L., G.B., K.G., J.D.S.), Cleveland Clinic, OH
| | - Jonathan D Smith
- From the Department of Cellular and Molecular Medicine (S.W.L., G.B., K.G., J.D.S.), Cleveland Clinic, OH.,Department of Cardiovascular Medicine (J.D.S.), Cleveland Clinic, OH
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Huber RJ, Mathavarajah S. Comparative transcriptomics reveals mechanisms underlying cln3-deficiency phenotypes in Dictyostelium. Cell Signal 2019; 58:79-90. [PMID: 30771446 DOI: 10.1016/j.cellsig.2019.02.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2018] [Revised: 01/29/2019] [Accepted: 02/09/2019] [Indexed: 12/28/2022]
Abstract
Mutations in CLN3 cause a juvenile form of neuronal ceroid lipofuscinosis (NCL). This devastating neurological disorder, commonly known as Batten disease, is currently untreatable due to a lack of understanding of the physiological role of the protein. Recently, work in the social amoeba Dictyostelium discoideum has provided valuable new insight into the function of CLN3 in the cell. More specifically, research has linked the Dictyostelium homolog (gene: cln3, protein: Cln3) to protein secretion, adhesion, and aggregation during starvation, which initiates multicellular development. In this study, we used comparative transcriptomics to explore the mechanisms underlying the aberrant response of cln3- cells to starvation. During starvation, 1153 genes were differentially expressed in cln3- cells compared to WT. Among the differentially expressed genes were homologs of other human NCL genes including TPP1/CLN2, CLN5, CTSD/CLN10, PGRN/CLN11, and CTSF/CLN13. STRING and GO term analyses revealed an enrichment of genes linked to metabolic, biosynthetic, and catalytic processes. We then coupled the findings from the RNA-seq analysis to biochemical assays, specifically showing that loss of cln3 affects the expression and activity of lysosomal enzymes, increases endo-lysosomal pH, and alters nitric oxide homeostasis. Finally, we show that cln3- cells accumulate autofluorescent storage bodies during starvation and provide evidence linking the function of Cln3 to Tpp1 and CtsD activity. In total, this study enhances our knowledge of the molecular mechanisms underlying Cln3 function in Dictyostelium.
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Affiliation(s)
- Robert J Huber
- Department of Biology, Trent University, Peterborough, Ontario, Canada.
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Moran-Reyna A, Coker JA. The effects of extremes of pH on the growth and transcriptomic profiles of three haloarchaea. F1000Res 2014; 3:168. [PMID: 25285207 PMCID: PMC4176423 DOI: 10.12688/f1000research.4789.2] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 08/26/2014] [Indexed: 12/03/2022] Open
Abstract
The halophilic archaea (haloarchaea) live in saline environments, which are found across the globe. In addition to salinity, these niches can be quite dynamic and experience extreme conditions such as low oxygen content, radiation (gamma and UV), pH and temperature. However, of all the naturally occurring stresses faced by the haloarchaea, only one, pH, has not been previously investigated in regard to the changes induced in the transcriptome. Therefore, we endeavored to determine the responses in three haloarchaea:
Halorubrum lacusprofundi (Hla),
Haloferax volcanii (Hvo), and
Halobacterium sp. NRC-1 (NRC-1) to growth under acidic and alkaline pH. Our observations showed that the transcriptomes of Hvo and NRC-1 regulated stress, motility, and ABC transporters in a similar manner, which is in line with previous reports from other prokaryotes when grown in an acidic environment. However, the pattern for Hla was more species specific. For alkaline stress, all three haloarchaea responded in a manner similar to well-studied archaea and bacteria showing the haloarchaeal response was general to prokaryotes. Additionally, we performed an analysis on the changes in the transcriptomes of the three haloarchaea when shifting from one pH extreme to the other. The results showed that the transcriptomes of all three haloarchaea respond more similarly when moving from alkaline to acidic conditions compared to a shift in the opposite direction. Interestingly, our studies also showed that individual genes of multiple paralogous gene families (
tbp,
tfb,
orc/
cdc6, etc.) found in the haloarchaea were regulated under specific stresses thereby providing evidence that they modulate the response to various environmental stresses. The studies described here are the first to catalog the changes in the haloarchaeal transcriptomes under growth in extreme pH and help us understand how life is able to thrive under all conditions present on Earth and, if present, on extraterrestrial bodies as well.
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Affiliation(s)
- Aida Moran-Reyna
- Department of Biology, University of Alabama at Birmingham, Birmingham, AL, 35294-1170, USA
| | - James A Coker
- Department of Biology, University of Alabama at Birmingham, Birmingham, AL, 35294-1170, USA ; The Graduate School, University of Maryland, University College, Largo, MD, 20774, USA
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Miranda ER, Zhuchenko O, Toplak M, Santhanam B, Zupan B, Kuspa A, Shaulsky G. ABC transporters in Dictyostelium discoideum development. PLoS One 2013; 8:e70040. [PMID: 23967067 PMCID: PMC3743828 DOI: 10.1371/journal.pone.0070040] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Accepted: 06/13/2013] [Indexed: 12/15/2022] Open
Abstract
ATP-binding cassette (ABC) transporters can translocate a broad spectrum of molecules across the cell membrane including physiological cargo and toxins. ABC transporters are known for the role they play in resistance towards anticancer agents in chemotherapy of cancer patients. There are 68 ABC transporters annotated in the genome of the social amoeba Dictyostelium discoideum. We have characterized more than half of these ABC transporters through a systematic study of mutations in their genes. We have analyzed morphological and transcriptional phenotypes for these mutants during growth and development and found that most of the mutants exhibited rather subtle phenotypes. A few of the genes may share physiological functions, as reflected in their transcriptional phenotypes. Since most of the abc-transporter mutants showed subtle morphological phenotypes, we utilized these transcriptional phenotypes to identify genes that are important for development by looking for transcripts whose abundance was unperturbed in most of the mutants. We found a set of 668 genes that includes many validated D. discoideum developmental genes. We have also found that abcG6 and abcG18 may have potential roles in intercellular signaling during terminal differentiation of spores and stalks.
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Affiliation(s)
- Edward Roshan Miranda
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
- Graduate Program in Developmental Biology, Baylor College of Medicine, Houston, Texas, United States of America
| | - Olga Zhuchenko
- Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, United States of America
| | - Marko Toplak
- Faculty of Computer and Information Science, University of Ljubljana, Ljubljana, Slovenia
| | - Balaji Santhanam
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
- Graduate Program in Structural and Computational Biology and Molecular Biophysics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Blaz Zupan
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
- Faculty of Computer and Information Science, University of Ljubljana, Ljubljana, Slovenia
| | - Adam Kuspa
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
- Graduate Program in Developmental Biology, Baylor College of Medicine, Houston, Texas, United States of America
- Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, United States of America
| | - Gad Shaulsky
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
- Graduate Program in Developmental Biology, Baylor College of Medicine, Houston, Texas, United States of America
- Graduate Program in Structural and Computational Biology and Molecular Biophysics, Baylor College of Medicine, Houston, Texas, United States of America
- * E-mail:
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7
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Kelsey JS, Fastman NM, Noratel EF, Blumberg DD. Ndm, a coiled-coil domain protein that suppresses macropinocytosis and has effects on cell migration. Mol Biol Cell 2012; 23:3407-19. [PMID: 22809629 PMCID: PMC3431939 DOI: 10.1091/mbc.e12-05-0392] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The ampA gene has a role in cell migration in Dictyostelium discoideum. Cells overexpressing AmpA show an increase in cell migration, forming large plaques on bacterial lawns. A second-site suppressor of this ampA-overexpressing phenotype identified a previously uncharacterized gene, ndm, which is described here. The Ndm protein is predicted to contain a coiled-coil BAR-like domain-a domain involved in endocytosis and membrane bending. ndm-knockout and Ndm-monomeric red fluorescent protein-expressing cell lines were used to establish a role for ndm in suppressing endocytosis. An increase in the rate of endocytosis and in the number of endosomes was detected in ndm(-) cells. During migration ndm(-) cells formed numerous endocytic cups instead of the broad lamellipodia structure characteristic of moving cells. A second lamellipodia-based function-cell spreading-was also defective in the ndm(-) cells. The increase in endocytosis and the defect in lamellipodia formation were associated with reduced chemotaxis in ndm(-) cells. Immunofluorescence results and glutathione S-transferase pull-down assays revealed an association of Ndm with coronin and F-actin. The results establish ndm as a gene important in regulating the balance between formation of endocytic cups and lamellipodia structures.
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Affiliation(s)
- Jessica S Kelsey
- Department of Biological Sciences, University of Maryland, Baltimore County, Baltimore, MD 21250, USA
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8
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Evidence of an evolutionarily conserved LMBR1 domain-containing protein that associates with endocytic cups and plays a role in cell migration in dictyostelium discoideum. EUKARYOTIC CELL 2012; 11:401-16. [PMID: 22307974 DOI: 10.1128/ec.05186-11] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The ampA gene plays a role in Dictyostelium discoideum cell migration. Loss of ampA function results in reduced ability of growing cells to migrate to folic acid and causes small plaques on bacterial lawns, while overexpression of AmpA results in a rapid-migration phenotype and correspondingly larger plaques than seen with wild-type cells. To help understand how the ampA gene functions, second-site suppressors were created by restriction enzyme-mediated integration (REMI) mutagenesis. These mutants were selected for their ability to reduce the large plaque size of the AmpA overexpresser strain. The lmbd2B gene was identified as a suppressor of an AmpA-overexpressing strain. The lmbd2B gene product belongs to the evolutionarily conserved LMBR1 protein family, some of whose known members are endocytic receptors associated with human diseases, such as anemia. In order to understand lmbd2B function, mRFP fusion proteins were created and lmbd2B knockout cell lines were established. Our findings indicate that the LMBD2B protein is found associated with endocytic cups. It colocalizes with proteins that play key roles in endocytic events and is localized to ruffles on the dorsal surfaces of growing cells. Vegetative lmbd2B-null cells display defects in cell migration. These cells have difficulty sensing the chemoattractant folic acid, as indicated by a decrease in their chemotactic index. lmbd2B-null cells also appear to have difficulty establishing a front/back orientation to facilitate migration. A role for lmbd2B in development is also suggested. Our research gives insight into the function of a previously uncharacterized branch of the LMBR1 family of proteins. We provide evidence of an LMBR1 family plasma membrane protein that associates with endocytic cups and plays a role in chemotaxis.
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9
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Paxillin and phospholipase D interact to regulate actin-based processes in Dictyostelium discoideum. EUKARYOTIC CELL 2011; 10:977-84. [PMID: 21531871 DOI: 10.1128/ec.00282-10] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The actin cytoskeleton forms a membrane-associated network whose proper regulation is essential for numerous processes, including cell differentiation, proliferation, adhesion, chemotaxis, endocytosis, exocytosis, and multicellular development. In this report, we show that in Dictyostelium discoideum, paxillin (PaxB) and phospholipase D (PldB) colocalize and coimmunoprecipitate, suggesting that they interact physically. Additionally, the phenotypes observed during development, cell sorting, and several actin-required processes, including cyclic AMP (cAMP) chemotaxis, cell-substrate adhesion, actin polymerization, phagocytosis, and exocytosis, reveal a genetic interaction between paxB and pldB, suggesting a functional interaction between their gene products. Taken together, our data point to PldB being a required binding partner of PaxB during processes involving actin reorganization.
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10
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Campos-Salinas J, Cabello-Donayre M, García-Hernández R, Pérez-Victoria I, Castanys S, Gamarro F, Pérez-Victoria JM. A new ATP-binding cassette protein is involved in intracellular haem trafficking in Leishmania. Mol Microbiol 2011; 79:1430-44. [PMID: 21255121 DOI: 10.1111/j.1365-2958.2010.07531.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The characterization of LABCG5, a new intracellular ATP-binding cassette protein in Leishmania donovani, is described. Unlike other ABCG half-transporters, LABCG5 is not involved in either drug resistance or phospholipid efflux. However, we provide evidence suggesting that this protein is involved in intracellular haem trafficking. Thus, downregulation of LABCG5 function produced upon overexpression of an inactive version of the protein caused a dramatic growth arrest unless a haemin supplement was added or the mutated gene was eliminated. Supplementation with haemoglobin, an upstream metabolite normally sufficient to meet parasite haem requirements, was unable to rescue the growth defect phenotype. Haemoglobin endocytosis was not hampered in dominant-negative parasites and neither was haem uptake, a process that we show here to be dependent on a specific transporter. In contrast, LABCG5 function was required for the correct intracellular trafficking of haemoglobin-bound porphyrins to the mitochondria, not affecting the routing of free haem. Finally, LABCG5 binds haem through hydrophobic and electrostatic interactions. Altogether, these data suggest that LABCG5 is involved in the salvage of the haem released after the breakdown of internalized haemoglobin. As Leishmania is auxotrophic for haem, the pharmacological targeting of this route could represent a novel approach to control fatal visceral leishmaniasis.
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Affiliation(s)
- Jenny Campos-Salinas
- Instituto de Parasitología y Biomedicina 'López-Neyra', CSIC, Parque Tecnológico de Ciencias de la Salud, Avda. del Conocimiento s/n, 18100 Armilla, Granada, Spain
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11
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Abstract
Much remains to be understood about how a group of cells break symmetry and differentiate into distinct cell types. The simple eukaryote Dictyostelium discoideum is an excellent model system for studying questions such as cell type differentiation. Dictyostelium cells grow as single cells. When the cells starve, they aggregate to develop into a multicellular structure with only two main cell types: spore and stalk. There has been a longstanding controversy as to how a cell makes the initial choice of becoming a spore or stalk cell. In this review, we describe how the controversy arose and how a consensus developed around a model in which initial cell type choice in Dictyostelium is dependent on the cell cycle phase that a cell happens to be in at the time that it starves.
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12
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Dictyostelium discoideum paxillin regulates actin-based processes. Protist 2009; 160:221-32. [PMID: 19213599 DOI: 10.1016/j.protis.2008.09.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2008] [Accepted: 09/13/2008] [Indexed: 10/21/2022]
Abstract
Paxillin is a key player in integrating the actin cytoskeleton with adhesion, and thus is essential to numerous cellular processes, including proliferation, differentiation, and migration in animal cells. PaxB, the Dictyostelium discoideum orthologue of paxillin, has been shown to be important for adhesion and development, much like its mammalian counterpart. Here, we use the overproduction of PaxB to gain better insight into its role in regulating the actin cytoskeleton and adhesion. We find that PaxB-overexpressing (PaxBOE) cells can aggregate and form mounds normally, but are blocked in subsequent development. This arrest can be rescued by addition of wild-type cells, indicating a non-cell autonomous role for PaxB. PaxBOE cells also have alterations in several actin-based processes, including adhesion, endocytosis, motility, and chemotaxis. PaxBOE cells exhibit an EDTA-sensitive increase in cell-cell cohesion, suggesting that PaxB-mediated adhesion is Ca(2+) or Mg(2+) dependent. Interestingly, cells overexpressing paxB are less adhesive to the substratum. In addition, PaxBOE cells display decreased motility under starved conditions, decreased endocytosis, and are unable to efficiently chemotax up a folate gradient. Taken together, the data suggest that proper expression of PaxB is vital for the regulation of development and actin-dependent processes.
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13
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Schroeder LK, Kremer S, Kramer MJ, Currie E, Kwan E, Watts JL, Lawrenson AL, Hermann GJ. Function of the Caenorhabditis elegans ABC transporter PGP-2 in the biogenesis of a lysosome-related fat storage organelle. Mol Biol Cell 2007; 18:995-1008. [PMID: 17202409 PMCID: PMC1805080 DOI: 10.1091/mbc.e06-08-0685] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Caenorhabditis elegans gut granules are intestine specific lysosome-related organelles with birefringent and autofluorescent contents. We identified pgp-2, which encodes an ABC transporter, in screens for genes required for the proper formation of gut granules. pgp-2(-) embryos mislocalize birefringent material into the intestinal lumen and are lacking in acidified intestinal V-ATPase-containing compartments. Adults without pgp-2(+) function similarly lack organelles with gut granule characteristics. These cellular phenotypes indicate that pgp-2(-) animals are defective in gut granule biogenesis. Double mutant analysis suggests that pgp-2(+) functions in parallel with the AP-3 adaptor complex during gut granule formation. We find that pgp-2 is expressed in the intestine where it functions in gut granule biogenesis and that PGP-2 localizes to the gut granule membrane. These results support a direct role of an ABC transporter in regulating lysosome biogenesis. Previously, pgp-2(+) activity has been shown to be necessary for the accumulation of Nile Red-stained fat in C. elegans. We show that gut granules are sites of fat storage in C. elegans embryos and adults. Notably, levels of triacylglycerides are relatively normal in animals defective in the formation of gut granules. Our results provide an explanation for the loss of Nile Red-stained fat in pgp-2(-) animals as well as insight into the specialized function of this lysosome-related organelle.
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Affiliation(s)
| | - Susan Kremer
- Program in Biochemistry and Molecular Biology, Lewis and Clark College, Portland, OR 97219; and
| | - Maxwell J. Kramer
- Program in Biochemistry and Molecular Biology, Lewis and Clark College, Portland, OR 97219; and
| | - Erin Currie
- *Department of Biology and
- Program in Biochemistry and Molecular Biology, Lewis and Clark College, Portland, OR 97219; and
| | - Elizabeth Kwan
- Program in Biochemistry and Molecular Biology, Lewis and Clark College, Portland, OR 97219; and
| | - Jennifer L. Watts
- Institute of Biological Chemistry, Washington State University, Pullman, WA 99164
| | | | - Greg J. Hermann
- *Department of Biology and
- Program in Biochemistry and Molecular Biology, Lewis and Clark College, Portland, OR 97219; and
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14
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Strmecki L, Greene DM, Pears CJ. Developmental decisions in Dictyostelium discoideum. Dev Biol 2005; 284:25-36. [PMID: 15964562 DOI: 10.1016/j.ydbio.2005.05.011] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2005] [Revised: 04/14/2005] [Accepted: 05/06/2005] [Indexed: 11/28/2022]
Abstract
Dictyostelium discoideum is an excellent system in which to study developmental decisions. Synchronous development is triggered by starvation and rapidly generates a limited number of cell types. Genetic and image analyses have revealed the elegant intricacies associated with this simple development system. Key signaling pathways identified as regulating cell fate decisions are likely to be conserved with metazoa and are providing insight into differentiation decisions under circumstances where considerable cell movement takes place during development.
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Affiliation(s)
- Lana Strmecki
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
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Li Z, Solomon JM, Isberg RR. Dictyostelium discoideum strains lacking the RtoA protein are defective for maturation of the Legionella pneumophila replication vacuole. Cell Microbiol 2005; 7:431-42. [PMID: 15679845 DOI: 10.1111/j.1462-5822.2004.00472.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
To identify host proteins involved in Legionella pneumophila intracellular replication, the soil amoeba Dictyostelium discoideum was analysed. The absence of the amoebal RtoA protein is demonstrated here to depress L. pneumophila intracellular growth. Uptake of L. pneumophila into a D. discoideum rtoA(-) strain was marginally defective, but this effect was not sufficient to account for the defective intracellular growth of L. pneumophila. The rtoA mutant was also more resistant to high-multiplicity killing by the bacterium. A targeting assay testing the colocalization of L. pneumophila-containing vacuole with an endoplasmic reticulum/pre-Golgi intermediate compartment marker protein, GFP-HDEL, was used to analyse these defects. In parental D. discoideum, the L. pneumophila vacuole showed recruitment of GFP-HDEL within 40 min after introduction of bacteria to the amoebae. By 6 h after infection it was clear that the rtoA mutant acquired and retained the GFP-HDEL less efficiently than the parental strain, and that the mutant was defective for promoting the physical expansion of the membranous compartment surrounding the bacteria. Depressed intracellular growth of L. pneumophila in a D. discoideum rtoA(-) mutant therefore appeared to result from a lowered efficiency of vesicle trafficking events that are essential for the modification and expansion of the L. pneumophila-containing compartment.
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Affiliation(s)
- Zhiru Li
- Howard Hughes Medical Institute, Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 150 Harrison Ave., Boston, MA 02111, USA
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Sultana H, Rivero F, Blau-Wasser R, Schwager S, Balbo A, Bozzaro S, Schleicher M, Noegel AA. Cyclase-Associated Protein is Essential for the Functioning of the Endo-Lysosomal System and Provides a Link to the Actin Cytoskeleton. Traffic 2005; 6:930-46. [PMID: 16138906 DOI: 10.1111/j.1600-0854.2005.00330.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Data from mutant analysis in yeast and Dictyostelium indicate a role for the cyclase-associated protein (CAP) in endocytosis and vesicle transport. We have used genetic and biochemical approaches to identify novel interacting partners of Dictyostelium CAP to help explain its molecular interactions in these processes. Cyclase-associated protein associates and interacts with subunits of the highly conserved vacuolar H(+)-ATPase (V-ATPase) and co-localizes to some extent with the V-ATPase. Furthermore, CAP is essential for maintaining the structural organization, integrity and functioning of the endo-lysosomal system, as distribution and morphology of V-ATPase- and Nramp1-decorated membranes were disturbed in a CAP mutant (CAP bsr) accompanied by an increased endosomal pH. Moreover, concanamycin A (CMA), a specific inhibitor of the V-ATPase, had a more severe effect on CAP bsr than on wild-type cells, and the mutant did not show adaptation to the drug. Also, the distribution of green fluorescent protein-CAP was affected upon CMA treatment in the wildtype and recovered after adaptation. Distribution of the V-ATPase in CAP bsr was drastically altered upon hypo-osmotic shock, and growth was slower and reached lower saturation densities in the mutant under hyper-osmotic conditions. Taken together, our data unravel a link of CAP with the actin cytoskeleton and endocytosis and suggest that CAP is an essential component of the endo-lysosomal system in Dictyostelium.
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Affiliation(s)
- Hameeda Sultana
- Center for Biochemistry and Center for Molecular Medicine Cologne, Medical Faculty, University of Cologne, 50931 Köln, Germany
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Steenbergen JN, Nosanchuk JD, Malliaris SD, Casadevall A. Cryptococcus neoformans virulence is enhanced after growth in the genetically malleable host Dictyostelium discoideum. Infect Immun 2003; 71:4862-72. [PMID: 12933827 PMCID: PMC187309 DOI: 10.1128/iai.71.9.4862-4872.2003] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cryptococcus neoformans is an encapsulated, environmental fungus that can cause life-threatening meningitis. Pathogenicity of C. neoformans for macrophages and vertebrate hosts may be a mechanism selected in evolution for protection against environmental predators. In this study, we investigated whether Dictyostelium discoideum could serve as an alternate host for C. neoformans. D. discoideum has a defined genetic system which provides significant advantages for the study of fungus-amoeba interactions. Our results show that D. discoideum is susceptible to infection with C. neoformans and that the interactions are similar to those described previously for this fungus with macrophages and Acanthamoeba castellanii. Acapsular C. neoformans cells did not replicate when coincubated with D. discoideum. However, incubation of acapsular C. neoformans with D. discoideum mutants defective in myosin VII synthesis resulted in infection, validating the concept that avirulent organisms can be virulent in impaired hosts even at the unicellular level. Phagocytosis of C. neoformans by D. discoideum could be inhibited with capsule-specific antibodies and various sugars. Passage of an encapsulated C. neoformans strain through D. discoideum cultures increased virulence and was accompanied by larger capsules and faster time to melanization. These results add to the evidence implicating soil ameboid predators as important factors for the maintenance of C. neoformans virulence in the environment and suggest that D. discoideum promises to be an extremely useful system for studying the interaction of C. neoformans with phagocytic cells.
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Affiliation(s)
- Judith N Steenbergen
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York 10461,USA
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Abstract
Endocytosis in protozoa is often regarded as largely different from the pathways operating in mammalian cells. Experiments in the amoeba Dictyostelium, one of the genetically tractable single-celled organisms, have allowed us to manipulate the flow through endocytic compartments and to study the dynamic distribution of molecules by means of green fluorescent protein fusions. This review attempts to compile the molecular data available from Dictyostelium and assign them to specific steps of internalization by phagocytosis or macropinocytosis and to subsequent stages of the endocytic pathway. Parallels to phagocytes of the mammalian immune system are emphasized. The major distinctive feature between mammalian phagocytes and free-living cells is the need for osmoregulation. Therefore Dictyostelium cells possess a contractile vacuole that has occasionally obscured analysis of endocytosis but is now found to be entirely separate from endocytic organelles. In conclusion, the potential of Dictyostelium amoebas to provide a model system of mammalian phagocytes is ever increasing.
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Affiliation(s)
- Markus Maniak
- Department of Cell Biology, Universitaet Kassel, 34109 Kassel, Germany
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Abstract
The endocytic pathway in Dictyostelium appears as a short circuit between endocytosis and exocytosis. Within the hour that elapses between internalization of nutrients and release of remnants, digestion by lysosomal enzymes occurs. Meanwhile, the maturing endosome undergoes a complex series of fusion and fission events, which change its character profoundly and which are far from being fully understood. This review attempts to order the dynamic events into a sequence of stages that is most consistent with present knowledge.
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Affiliation(s)
- Markus Maniak
- Abt. Zellbiologie, Universität Kassel, Heinrich-Plett-Str. 40, 34132 Kassel, Germany.
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Anjard C, Loomis WF. Evolutionary analyses of ABC transporters of Dictyostelium discoideum. EUKARYOTIC CELL 2002; 1:643-52. [PMID: 12456012 PMCID: PMC117992 DOI: 10.1128/ec.1.4.643-652.2002] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The ABC superfamily of genes is one of the largest in the genomes of both bacteria and eukaryotes. The proteins encoded by these genes all carry a characteristic 200- to 250-amino-acid ATP-binding cassette that gives them their family name. In bacteria they are mostly involved in nutrient import, while in eukaryotes many are involved in export. Seven different families have been defined in eukaryotes based on sequence homology, domain topology, and function. While only 6 ABC genes in Dictyostelium discoideum have been studied in detail previously, sequences from the well-advanced Dictyostelium genome project have allowed us to recognize 68 members of this superfamily. They have been classified and compared to animal, plant, and fungal orthologs in order to gain some insight into the evolution of this superfamily. It appears that many of the genes inferred to have been present in the ancestor of the crown organisms duplicated extensively in some but not all phyla, while others were lost in one lineage or the other.
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Affiliation(s)
- Christophe Anjard
- Center for Molecular Genetics, Division of Biology, University of California--San Diego, La Jolla, California 92093-0368, USA
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Kirk K, Saliba KJ. Chloroquine resistance and the pH of the malaria parasite's digestive vacuole. Drug Resist Updat 2001; 4:335-7. [PMID: 12030781 DOI: 10.1054/drup.2002.0234] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The molecular mechanisms underlying chloroquine resistance in the malaria parasite are not well understood. Recent studies have focused attention on the role of the pH of the parasite's 'digestive vacuole', an internal acidic compartment in which ingested host cell proteins are degraded. In these studies, vacuolar pH was estimated from measurements of fluorescence from parasites stained with acridine orange. The validity of the method, and the conclusions drawn, have been challenged. Nevertheless, the correlation observed between acridine orange fluorescence and chloroquine resistance is intriguing and may well provide insights into the resistance mechanism. Whether vacuolar pH plays a role in chloroquine resistance remains an open question.
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Affiliation(s)
- K Kirk
- School of Biochemistry and Molecular Biology, Faculty of Science, Australian National University, Canberra, A.C.T. 0200, Australia.
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