1
|
Iriarte LS, Martinez CI, de Miguel N, Coceres VM. Tritrichomonas foetus Cell Division Involves DNA Endoreplication and Multiple Fissions. Microbiol Spectr 2023; 11:e0325122. [PMID: 36728437 PMCID: PMC10100903 DOI: 10.1128/spectrum.03251-22] [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: 08/26/2022] [Accepted: 01/16/2023] [Indexed: 02/03/2023] Open
Abstract
Tritrichomonas foetus and Trichomonas vaginalis are extracellular flagellated parasites that inhabit animals and humans, respectively. Cell division is a crucial process in most living organisms that leads to the formation of 2 daughter cells from a single mother cell. It has been assumed that T. vaginalis and T. foetus modes of reproduction are exclusively by binary fission. However, here, we showed that multinuclearity is a phenomenon regularly observed in different T. foetus and T. vaginalis strains in standard culture conditions. Additionally, we revealed that nutritional depletion or nutritional deprivation led to different dormant phenotypes. Although multinucleated T. foetus are mostly observed during nutritional depletion, numerous cells with 1 larger nucleus have been observed under nutritional deprivation conditions. In both cases, when the standard culture media conditions are restored, the cytoplasm of these multinucleated cells separates, and numerous parasites are generated in a short period of time by the fission multiple. We also revealed that DNA endoreplication occurs both in large and multiple nuclei of parasites under nutritional deprivation and depletion conditions, suggesting an important function in stress nutritional situations. These results provide valuable data about the cell division process of these extracellular parasites. IMPORTANCE Nowadays, it's known that T. foetus and T. vaginalis generate daughter cells by binary fission. Here, we report that both parasites are also capable of dividing by multiple fission under stress conditions. We also demonstrated, for the first time, that T. foetus can increase its DNA content per parasite without concluding the cytokinesis process (endoreplication) under stress conditions, which represents an efficient strategy for subsequent fast multiplication when the context becomes favorable. Additionally, we revealed the existence of novel dormant forms of resistance (multinucleated or mononucleated polyploid parasites), different than the previously described pseudocysts, that are formed under stress conditions. Thus, it is necessary to evaluate the role of these structures in the parasites' transmission in the future.
Collapse
Affiliation(s)
- Lucrecia S. Iriarte
- Laboratorio de Parásitos Anaerobios, Instituto Tecnológico Chascomús (INTECH), CONICET-UNSAM, Chascomús, Argentina
- Escuela de Bio y Nanotecnologías, Universidad Nacional de San Martin (UNSAM), Buenos Aires, Argentina
| | - Cristian I. Martinez
- Laboratorio de Parásitos Anaerobios, Instituto Tecnológico Chascomús (INTECH), CONICET-UNSAM, Chascomús, Argentina
- Escuela de Bio y Nanotecnologías, Universidad Nacional de San Martin (UNSAM), Buenos Aires, Argentina
| | - Natalia de Miguel
- Laboratorio de Parásitos Anaerobios, Instituto Tecnológico Chascomús (INTECH), CONICET-UNSAM, Chascomús, Argentina
- Escuela de Bio y Nanotecnologías, Universidad Nacional de San Martin (UNSAM), Buenos Aires, Argentina
| | - Veronica M. Coceres
- Laboratorio de Parásitos Anaerobios, Instituto Tecnológico Chascomús (INTECH), CONICET-UNSAM, Chascomús, Argentina
- Escuela de Bio y Nanotecnologías, Universidad Nacional de San Martin (UNSAM), Buenos Aires, Argentina
| |
Collapse
|
2
|
Molecular characterization of EhAK6, an endonuclease V domain-containing aurora kinase protein from Entamoeba histolytica: Protein-protein interaction, docking and functional aspect. CURRENT RESEARCH IN BIOTECHNOLOGY 2021. [DOI: 10.1016/j.crbiot.2021.07.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
|
3
|
Hammarton TC. Who Needs a Contractile Actomyosin Ring? The Plethora of Alternative Ways to Divide a Protozoan Parasite. Front Cell Infect Microbiol 2019; 9:397. [PMID: 31824870 PMCID: PMC6881465 DOI: 10.3389/fcimb.2019.00397] [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] [Received: 09/03/2019] [Accepted: 11/06/2019] [Indexed: 01/21/2023] Open
Abstract
Cytokinesis, or the division of the cytoplasm, following the end of mitosis or meiosis, is accomplished in animal cells, fungi, and amoebae, by the constriction of an actomyosin contractile ring, comprising filamentous actin, myosin II, and associated proteins. However, despite this being the best-studied mode of cytokinesis, it is restricted to the Opisthokonta and Amoebozoa, since members of other evolutionary supergroups lack myosin II and must, therefore, employ different mechanisms. In particular, parasitic protozoa, many of which cause significant morbidity and mortality in humans and animals as well as considerable economic losses, employ a wide diversity of mechanisms to divide, few, if any, of which involve myosin II. In some cases, cell division is not only myosin II-independent, but actin-independent too. Mechanisms employed range from primitive mechanical cell rupture (cytofission), to motility- and/or microtubule remodeling-dependent mechanisms, to budding involving the constriction of divergent contractile rings, to hijacking host cell division machinery, with some species able to utilize multiple mechanisms. Here, I review current knowledge of cytokinesis mechanisms and their molecular control in mammalian-infective parasitic protozoa from the Excavata, Alveolata, and Amoebozoa supergroups, highlighting their often-underappreciated diversity and complexity. Billions of people and animals across the world are at risk from these pathogens, for which vaccines and/or optimal treatments are often not available. Exploiting the divergent cell division machinery in these parasites may provide new avenues for the treatment of protozoal disease.
Collapse
Affiliation(s)
- Tansy C Hammarton
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| |
Collapse
|
4
|
Hetero-oligomer of dynamin-related proteins participates in the fission of highly divergent mitochondria from Entamoeba histolytica. Sci Rep 2017; 7:13439. [PMID: 29044162 PMCID: PMC5647421 DOI: 10.1038/s41598-017-13721-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Accepted: 09/27/2017] [Indexed: 11/09/2022] Open
Abstract
Entamoeba histolytica is an anaerobic parasitic protist and possesses mitosomes, one of the most highly divergent mitochondrion-related organelles (MROs). Although unique metabolism and protein/metabolite transport machinery have been demonstrated in Entamoeba mitosomes, the mechanism of mitosomal fusion and fission remains to be elucidated. In this study, we demonstrate that two dynamin-related proteins (DRPs) are cooperatively involved in the fission of Entamoeba mitosomes. Expression of a dominant negative form of EhDrpA and EhDrpB, and alternatively, repression of gene expression of EhDrpA and EhDrpB genes, caused elongation of mitosomes, reflecting inhibition of mitosomal fission. Moreover, EhDrpA and EhDrpB formed an unprecedented hetero-oligomeric complex with an approximate 1:2 to 1:3 ratio, suggesting that the observed elongation of mitosomes is likely caused by the disruption and instability of the complex caused by an imbalance in the two DRPs. Altogether, this is the first report of a hetero-oligomeric DRP complex which participates in the fission of mitochondria and MROs.
Collapse
|
5
|
Verma D, Murmu A, Gourinath S, Bhattacharya A, Chary KVR. Structure of Ca2+-binding protein-6 from Entamoeba histolytica and its involvement in trophozoite proliferation regulation. PLoS Pathog 2017; 13:e1006332. [PMID: 28505197 PMCID: PMC5444848 DOI: 10.1371/journal.ppat.1006332] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Revised: 05/25/2017] [Accepted: 04/03/2017] [Indexed: 12/01/2022] Open
Abstract
Cell cycle of Entamoeba histolytica, the etiological agent of amoebiasis, follows a novel pathway, which includes nuclear division without the nuclear membrane disassembly. We report a nuclear localized Ca2+-binding protein from E. histolytica (abbreviated hereafter as EhCaBP6), which is associated with microtubules. We determined the 3D solution NMR structure of EhCaBP6, and identified one unusual, one canonical and two non-canonical cryptic EF-hand motifs. The cryptic EF-II and EF-IV pair with the Ca2+-binding EF-I and EF-III, respectively, to form a two-domain structure similar to Calmodulin and Centrin proteins. Downregulation of EhCaBP6 affects cell proliferation by causing delays in transition from G1 to S phase, and inhibition of DNA synthesis and cytokinesis. We also demonstrate that EhCaBP6 modulates microtubule dynamics by increasing the rate of tubulin polymerization. Our results, including structural inferences, suggest that EhCaBP6 is an unusual CaBP involved in regulating cell proliferation in E. histolytica similar to nuclear Calmodulin. E. histolytica, the etiological agent of amoebiasis, is a protozoan parasite responsible for around 100,000 deaths per year in developing nations. Though the organism has been identified more than 100 years back, there is not much understanding about the biology of this organism. Calcium signaling plays an important role in the biology of this organism. Here we show structure-functional relationship of one of the Ca2+-binding proteins (abbreviated as EhCaBP6) and suggest its involvement in cell division in this parasite. EhCaBP6, a nucleo-cytosolic Ca2+-binding protein, is a microtubule end binding protein and overexpression of its gene induces an increase in number of microtubular assemblies in E. histolytica. Cell division cycle in E. histolytica occurs along the microtubular structures without disruption of nuclear envelope. Occurrence of multinucleated cells in culture suggests duplication and reduplication of nuclear DNA without cytokinesis. Although Kinesin like protein (Klp1), Formin1 and EhCaBP6 were shown to be part of the microtubular assembly, their role in regulation of the cell cycle is not yet documented. Further, E. histolytica does not have a typical CaM like protein. However, the 3D structure of EhCaBP6 with two Ca2+-binding sites is similar to CaM, in spite of their low sequence similarity. Here, we demonstrate that EhCaBP6 regulates cell cycle specifically by facilitating DNA synthesis, transition from G1 to S phase and cytokinesis. The structural and functional similarity between EhCaBP6 and CaM suggests EhCaBP6 to be a functional homologue of nuclear CaM with important roles in regulation of cell cycle.
Collapse
Affiliation(s)
- Deepshikha Verma
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Mumbai, India
- Tata Institute of Fundamental Research, Center for Interdisciplinary Sciences, Hyderabad, India
| | - Aruna Murmu
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
| | | | - Alok Bhattacharya
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Kandala V. R. Chary
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Mumbai, India
- Tata Institute of Fundamental Research, Center for Interdisciplinary Sciences, Hyderabad, India
- * E-mail:
| |
Collapse
|
6
|
Abstract
The outcome of an Entamoeba histolytica infection is variable and the contribution of genetic diversity within E. histolytica to human disease is not fully understood. The information provided by the whole genome sequence of the E. histolytica reference laboratory strain (HM-1:IMSS) and thirteen additional laboratory strains have been made publically available. In this review theories on the source of the unexpected level of structural diversity found in E. histolytica will be discussed.
Collapse
Affiliation(s)
- Carol A Gilchrist
- Department of Medicine, School of Medicine, University of Virginia, Charlottesville, Virginia, United States of America
| |
Collapse
|
7
|
Cruz OHDL, Marchat LA, Guillén N, Weber C, Rosas IL, Díaz-Chávez J, Herrera L, Rojo-Domínguez A, Orozco E, López-Camarillo C. Multinucleation and Polykaryon Formation is Promoted by the EhPC4 Transcription Factor in Entamoeba histolytica. Sci Rep 2016; 6:19611. [PMID: 26792358 PMCID: PMC4726151 DOI: 10.1038/srep19611] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Accepted: 12/14/2015] [Indexed: 02/01/2023] Open
Abstract
Entamoeba histolytica is the intestinal parasite responsible for human amoebiasis that is a leading cause of death in developing countries. In this protozoan, heterogeneity in DNA content, polyploidy and genome plasticity have been associated to alterations in mechanisms controlling DNA replication and cell division. Studying the function of the transcription factor EhPC4, we unexpectedly found that it is functionally related to DNA replication, and multinucleation. Site-directed mutagenesis on the FRFPKG motif revealed that the K127 residue is required for efficient EhPC4 DNA-binding activity. Remarkably, overexpression of EhPC4 significantly increased cell proliferation, DNA replication and DNA content of trophozoites. A dramatically increase in cell size resulting in the formation of giant multinucleated trophozoites (polykaryon) was also found. Multinucleation event was associated to cytokinesis failure leading to abortion of ongoing cell division. Consistently, genome-wide profiling of EhPC4 overexpressing trophozoites revealed the up-regulation of genes involved in carbohydrates and nucleic acids metabolism, chromosome segregation and cytokinesis. Forced overexpression of one of these genes, EhNUDC (nuclear movement protein), led to alterations in cytokinesis and partially recapitulated the multinucleation phenotype. These data indicate for the first time that EhPC4 is associated with events related to polyploidy and genome stability in E. histolytica.
Collapse
Affiliation(s)
| | - Laurence A. Marchat
- National Polytechnic Institute, National School of Medicine and Homeopathy, Institutional Program of Molecular Biomedicine, Biotechnology Program, Mexico City, Mexico
| | - Nancy Guillén
- Institut Pasteur, Cellular Biology of Parasitism Unit, Paris, France
- INSERM U786, Paris, France
| | - Christian Weber
- Institut Pasteur, Cellular Biology of Parasitism Unit, Paris, France
- INSERM U786, Paris, France
| | - Itzel López Rosas
- Universidad Autonoma de la Ciudad de Mexico, Genomics Sciences Program, Mexico City, Mexico
| | - José Díaz-Chávez
- National Institute of Cancerology, Carcinogenesis Laboratory, Mexico City, Mexico
| | - Luis Herrera
- National Institute of Cancerology, Carcinogenesis Laboratory, Mexico City, Mexico
| | - Arturo Rojo-Domínguez
- Metropolitan Autonomous University, Natural Sciences Department, Mexico City, Mexico
| | - Esther Orozco
- Center for Research and Advanced Studies of the National Polytechnic Institute, Department of Infectomics and Molecular Pathogenesis, Mexico City, Mexico
| | - César López-Camarillo
- Universidad Autonoma de la Ciudad de Mexico, Genomics Sciences Program, Mexico City, Mexico
| |
Collapse
|
8
|
Grewal JS, Padhan N, Aslam S, Bhattacharya A, Lohia A. The calcium binding protein EhCaBP6 is a microtubular-end binding protein inEntamoeba histolytica. Cell Microbiol 2013; 15:2020-33. [DOI: 10.1111/cmi.12167] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2012] [Revised: 06/28/2013] [Accepted: 07/08/2013] [Indexed: 11/30/2022]
Affiliation(s)
- Jaspreet Singh Grewal
- Department of Biochemistry; Bose Institute; P-1/12, C. I. T. Scheme VII-M Kolkata 700 054 India
| | - Narendra Padhan
- School of Life Sciences; Jawaharlal Nehru University; New Delhi India
| | - Saima Aslam
- School of Life Sciences; Jawaharlal Nehru University; New Delhi India
| | - Alok Bhattacharya
- School of Life Sciences; Jawaharlal Nehru University; New Delhi India
| | - Anuradha Lohia
- Department of Biochemistry; Bose Institute; P-1/12, C. I. T. Scheme VII-M Kolkata 700 054 India
| |
Collapse
|
9
|
Mukherjee C, Majumder S, Lohia A. Inter-cellular variation in DNA content of Entamoeba histolytica originates from temporal and spatial uncoupling of cytokinesis from the nuclear cycle. PLoS Negl Trop Dis 2009; 3:e409. [PMID: 19352422 PMCID: PMC2659751 DOI: 10.1371/journal.pntd.0000409] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2008] [Accepted: 03/11/2009] [Indexed: 11/19/2022] Open
Abstract
Accumulation of multiple copies of the genome in a single nucleus and several nuclei in a single cell has previously been noted in Entamoeba histolytica, contributing to the genetic heterogeneity of this unicellular eukaryote. In this study, we demonstrate that this genetic heterogeneity is an inherent feature of the cell cycle of this organism. Chromosome segregation occurs on a variety of novel microtubular assemblies including multi-polar spindles. Cytokinesis in E. histolytica is completed by the mechanical severing of a thin cytoplasmic bridge, either independently or with the help of neighboring cells. Importantly, cytokinesis is uncoupled from the nuclear division cycle, both temporally and spatially, leading to the formation of unequal daughter cells. Sorting of euploid and polyploid cells showed that each of these sub-populations acquired heterogeneous DNA content upon further growth. Our study conclusively demonstrates that genetic heterogeneity originates from the unique mode of cell division events in this protist. Proliferating eukaryotic cells regulate their DNA synthesis, chromosome segregation, and cell division with great precision so that daughter cells are genetically identical. Our study demonstrates that in proliferating cells of the protist pathogen Entamoeba histolytica re-duplication of DNA followed by segregation on atypical and diverse microtubular structures is frequently observed. In this parasite, cell division is erratic, so that each daughter cell may contain one or more nuclei and sometimes no nuclei. This uncoupling of cell cycle events and survival of daughter cells with unequal DNA contents leads to genetic heterogeneity in E. histolytica. Our study highlights the inherent plasticity of the Entamoeba genome and the ability of this protist to survive in the absence of strict regulatory mechanisms that are a hallmark of the eukaryotic cell cycle.
Collapse
Affiliation(s)
| | | | - Anuradha Lohia
- Department of Biochemistry, Bose Institute, Kolkata, India
- * E-mail:
| |
Collapse
|
10
|
Mukherjee C, Clark CG, Lohia A. Entamoeba shows reversible variation in ploidy under different growth conditions and between life cycle phases. PLoS Negl Trop Dis 2008; 2:e281. [PMID: 18714361 PMCID: PMC2500184 DOI: 10.1371/journal.pntd.0000281] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2008] [Accepted: 07/18/2008] [Indexed: 11/18/2022] Open
Abstract
Under axenic growth conditions, trophozoites of Entamoeba histolytica contain heterogenous amounts of DNA due to the presence of both multiple nuclei and different amounts of DNA in individual nuclei. In order to establish if the DNA content and the observed heterogeneity is maintained during different growth conditions, we have compared E. histolytica cells growing in xenic and axenic cultures. Our results show that the nuclear DNA content of E. histolytica trophozoites growing in axenic cultures is at least 10 fold higher than in xenic cultures. Re-association of axenic cultures with their bacterial flora led to a reduction of DNA content to the original xenic values. Thus switching between xenic and axenic growth conditions was accompanied by significant changes in the nuclear DNA content of this parasite. Changes in DNA content during encystation-excystation were studied in the related reptilian parasite E. invadens. During excystation of E. invadens cysts, it was observed that the nuclear DNA content increased approximately 40 fold following emergence of trophozoites in axenic cultures. Based on the observed large changes in nuclear size and DNA content, and the minor differences in relative abundance of representative protein coding sequences, rDNA and tRNA sequences, it appears that gain or loss of whole genome copies may be occurring during changes in the growth conditions. Our studies demonstrate the inherent plasticity and dynamic nature of the Entamoeba genome in at least two species. In contrast to the perception that DNA content of an organism is stable and maintained during different conditions and life cycle stages, new evidence shows that many organisms display changes in their DNA content at different stages of their life cycle. We have earlier identified intra-cellular and inter-cellular differences in DNA content of the protist pathogen Entamoeba histolytica and established that this organism can tolerate large variations in DNA content during axenic culture. In this study we have made an important advancement in the understanding of amoeba biology where we have shown that changes in growth conditions and life cycle stages are accompanied by large differences in DNA content involving gain or loss of whole genome copies. This property may well regulate the outcome of infection and subsequently the disease.
Collapse
Affiliation(s)
| | - C. Graham Clark
- Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Anuradha Lohia
- Department of Biochemistry, Bose Institute, Kolkata, India
- * E-mail:
| |
Collapse
|
11
|
Dastidar PG, Lohia A. Bipolar spindle frequency and genome content are inversely regulated by the activity of two N-type kinesins in Entamoeba histolytica. Cell Microbiol 2008; 10:1559-71. [PMID: 18363907 DOI: 10.1111/j.1462-5822.2008.01150.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Bipolar microtubular spindles are seen infrequently in Entamoeba histolytica trophozoites while monopolar or radial microtubular assemblies are common. Additionally, heterogeneity in nuclear DNA content and multi-nucleation is found in amoeba cells growing in axenic culture. Taken together these observations indicate that genome segregation is irregular in these cells. In order to identify proteins involved in regulating genome segregation, we have focused on studying E. histolytica homologues of kinesin motor proteins that are known to affect stability of bipolar mitotic spindles. We have demonstrated earlier that increased levels of the kinesin--Eh Klp5--led to increased frequency of bipolar spindles accompanied with a reduction in the heterogeneity of genome content, showing that bipolar spindle frequency was inversely linked to genome content in E. histolytica. In this study, we have investigated the role of E. histolytica kinesins (Eh KlpA1, 2-4) in regulating bipolar spindle frequency and genome content. While downregulation of Eh Klp3, 4 and A1 showed no effect, downregulation of Eh Klp2 led to increased frequency of bipolar spindles and homogenization of genome content, similar to the effect of increased expression of Eh Klp5. In addition to microtubules, Eh Klp2-4 associated with F-actin in the cytoplasm, suggesting that these kinesins are multi-functional.
Collapse
|
12
|
Entamoeba histolytica encodes unique formins, a subset of which regulates DNA content and cell division. Infect Immun 2008; 76:2368-78. [PMID: 18347041 DOI: 10.1128/iai.01449-07] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The formin family of proteins mediates dynamic changes in actin assembly in eukaryotes, and therefore it is important to understand the function of these proteins in Entamoeba histolytica, where actin forms the major cytoskeletal network. In this study we have identified the formin homologs encoded in the E. histolytica genome based on sequence analysis. Using multiple tools, we have analyzed the primary sequences of the eight E. histolytica formins and discovered three subsets: (i) E. histolytica formin-1 to -3 (Ehformin-1 to -3), (ii) Ehformin-4, and (iii) Ehformin-5 to -8. Two of these subsets (Ehformin-1 to -3 and Ehformin-4) showed significant sequence differences from their closest homologs, while Ehformin-5 to -8 were unique among all known formins. Since Ehformin-1 to -3 showed important sequence differences from Diaphanous-related formins (DRFs), we have studied the functions of Ehformin-1 and -2 in E. histolytica transformants. Like other DRFs, Ehformin-1 and -2 associated with F-actin in response to serum factors, in pseudopodia, in pinocytic and phagocytic vesicles, and at cell division sites. Ehformin-1 and -2 also localized with the microtubular assembly in the nucleus, indicating their involvement in genome segregation. While increased expression of Ehformin-1 and -2 did not affect phagocytosis or motility, it clearly showed an increase in the number of binucleated cells, the number of nuclei in multinucleated cells, and the average DNA content of each nucleus, suggesting that these proteins regulate both mitosis and cytokinesis in E. histolytica.
Collapse
|