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Wetzel DM, Schmidt J, Kuhlenschmidt MS, Dubey JP, Sibley LD. Gliding motility leads to active cellular invasion by Cryptosporidium parvum sporozoites. Infect Immun 2005; 73:5379-87. [PMID: 16113253 PMCID: PMC1231075 DOI: 10.1128/iai.73.9.5379-5387.2005] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We examined gliding motility and cell invasion by an early-branching apicomplexan, Cryptosporidium parvum, which causes diarrheal disease in humans and animals. Real-time video microscopy demonstrated that C. parvum sporozoites undergo circular and helical gliding, two of the three stereotypical movements exhibited by Toxoplasma gondii tachyzoites. C. parvum sporozoites moved more rapidly than T. gondii sporozoites, which showed the same rates of motility as tachyzoites. Motility by C. parvum sporozoites was prevented by latrunculin B and cytochalasin D, drugs that depolymerize the parasite actin cytoskeleton, and by the myosin inhibitor 2,3-butanedione monoxime. Imaging of the initial events in cell entry by Cryptosporidium revealed that invasion occurs rapidly; however, the parasite does not enter deep into the cytosol but rather remains at the cell surface in a membrane-bound compartment. Invasion did not stimulate rearrangement of the host cell cytoskeleton and was inhibited by cytochalasin D, even in host cells that were resistant to the drug. Our studies demonstrate that C. parvum relies on a conserved actin-myosin motor for motility and active penetration of its host cell, thus establishing that this is a widely conserved feature of the Apicomplexa.
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Affiliation(s)
- Dawn M Wetzel
- Department of Molecular Microbiology, Campus Box 8230, Washington University School of Medicine, St. Louis, MO 63110, USA
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52
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Smith HV, Nichols RAB, Grimason AM. Cryptosporidium excystation and invasion: getting to the guts of the matter. Trends Parasitol 2005; 21:133-42. [PMID: 15734661 DOI: 10.1016/j.pt.2005.01.007] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Cryptosporidium parvum excystation and host cell invasion have been characterized in some detail ultrastructurally. However, until recently, the biochemical and molecular basis of host-parasite interactions and parasite- and host-specific molecules involved in excystation, motility and host cell invasion have been poorly understood. This article describes our understanding of Cryptosporidium excystation and the events leading to host cell invasion, and draws from information available about these processes in other apicomplexans. Many questions remain but, once the specific mechanisms are identified, they could prove to be novel targets for drug delivery.
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Affiliation(s)
- Huw V Smith
- Scottish Parasite Diagnostic Laboratory, Stobhill Hospital, Glasgow G21 3UW, Scotland, UK.
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53
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Leirião P, Rodrigues CD, Albuquerque SS, Mota MM. Survival of protozoan intracellular parasites in host cells. EMBO Rep 2005; 5:1142-7. [PMID: 15577928 PMCID: PMC1299194 DOI: 10.1038/sj.embor.7400299] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2004] [Accepted: 10/25/2004] [Indexed: 12/30/2022] Open
Abstract
The most common human diseases are caused by pathogens. Several of these microorganisms have developed efficient ways in which to exploit host molecules, along with molecular pathways to ensure their survival, differentiation and replication in host cells. Although the contribution of the host cell to the development of many intracellular pathogens (particularly viruses and bacteria) has been unequivocally established, the study of host-cell requirements during the life cycle of protozoan parasites is still in its infancy. In this review, we aim to provide some insight into the manipulation of the host cell by parasites through discussing the hurdles that are faced by the latter during infection.
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Affiliation(s)
- Patrícia Leirião
- Instituto Gulbenkian de Ciência, Rua da Quinta Grande 6, 2780-156 Oeiras, Portugal
| | | | - Sónia S. Albuquerque
- Instituto Gulbenkian de Ciência, Rua da Quinta Grande 6, 2780-156 Oeiras, Portugal
| | - Maria M. Mota
- Instituto Gulbenkian de Ciência, Rua da Quinta Grande 6, 2780-156 Oeiras, Portugal
- Tel: +351 21 446 4517; Fax: +351 21 440 7970;
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Carabeo RA, Grieshaber SS, Hasenkrug A, Dooley C, Hackstadt T. Requirement for the Rac GTPase in Chlamydia trachomatis invasion of non-phagocytic cells. Traffic 2004; 5:418-25. [PMID: 15117316 DOI: 10.1111/j.1398-9219.2004.00184.x] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Chlamydiae are gram-negative obligate intracellular pathogens to which access to an intracellular environment is paramount to their survival and replication. To this end, chlamydiae have evolved extremely efficient means of invading nonphagocytic cells. To elucidate the host cell machinery utilized by Chlamydia trachomatis in invasion, we examined the roles of the Rho GTPase family members in the internalization of chlamydial elementary bodies. Upon binding of elementary bodies on the cell surface, actin is rapidly recruited to the sites of internalization. Members of the Rho GTPase family are frequently involved in localized recruitment of actin. Clostridial Toxin B, which is a known enzymatic inhibitor of Rac, Cdc42 and Rho GTPases, significantly reduced chlamydial invasion of HeLa cells. Expression of dominant negative constructs in HeLa cells revealed that chlamydial uptake was dependent on Rac, but not on Cdc42 or RhoA. Rac but not Cdc42 was found to be activated by chlamydial attachment. The effect of dominant negative Rac expression on chlamydial uptake is manifested through the inhibition of actin recruitment to the sites of chlamydial entry. Studies utilizing Green Fluorescent Protein fusion constructs of Rac, Cdc42 and RhoA, showed Rac to be the sole member of the Rho GTPase family recruited to the site of chlamydial entry.
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Affiliation(s)
- Rey A Carabeo
- Host-Parasite Interactions Section, Laboratory of Intracellular Parasites, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rocky Mountain Laboratories, Hamilton, MT 59840, USA
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55
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Hashim A, Clyne M, Mulcahy G, Akiyoshi D, Chalmers R, Bourke B. Host cell tropism underlies species restriction of human and bovine Cryptosporidium parvum genotypes. Infect Immun 2004; 72:6125-31. [PMID: 15385517 PMCID: PMC517554 DOI: 10.1128/iai.72.10.6125-6131.2004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
It has been recognized recently that human cryptosporidiosis is usually caused by Cryptosporidium parvum genotype I ("human" C. parvum), which is not found in animals. Compared to C. parvum genotype II, little is known of the biology of invasion of the human-restricted C. parvum genotype I. The aims of the present study were (i) to explore and compare with genotype II the pathogenesis of C. parvum genotype I infection by using an established in vitro model of infection and (ii) to examine the possibility that host-specific cell tropism determines species restriction among C. parvum genotypes by using a novel ex vivo small intestinal primary cell model of infection. Oocysts of C. parvum genotypes I and II were used to infect HCT-8 cells and primary intestinal epithelial cells in vitro. Primary cells were harvested from human endoscopic small-bowel biopsies and from bovine duodenum postmortem. C. parvum genotype I infected HCT-8 cells with lower efficiency than C. parvum genotype II. Actin colocalization at the host parasite interface and reduction in levels of invasion after treatment with microfilament inhibitors (cytochalasin B and cytochalasin D) were observed for both genotypes. C. parvum genotype II invaded primary intestinal epithelial cells, regardless of the species of origin. In contrast, C. parvum genotype I invaded only human small-bowel cells. The pathogenesis of C. parvum genotype I differs from C. parvum genotype II. C parvum genotype I does not enter primary bovine intestinal cells, suggesting that the species restriction of this genotype is due to host tissue tropism of the infecting isolate.
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Affiliation(s)
- Amna Hashim
- The Children's Research Centre, Our Lady's Hospital for Sick Children, Crumlin, Dublin, Ireland
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56
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Chen XM, Splinter PL, Tietz PS, Huang BQ, Billadeau DD, LaRusso NF. Phosphatidylinositol 3-Kinase and Frabin Mediate Cryptosporidium parvum Cellular Invasion via Activation of Cdc42. J Biol Chem 2004; 279:31671-8. [PMID: 15133042 DOI: 10.1074/jbc.m401592200] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cryptosporidium parvum invades target epithelia via a mechanism that involves host cell actin reorganization. We previously demonstrated that C. parvum activates the Cdc42/neural Wiskott-Aldrich syndrome protein network in host cells resulting in actin remodeling at the host cell-parasite interface, thus facilitating C. parvum cellular invasion. Here, we tested the role of phosphatidylinositol 3-kinase (PI3K) and frabin, a guanine nucleotide exchange factor specific for Cdc42 in the activation of Cdc42 during C. parvum infection of biliary epithelial cells. We found that C. parvum infection of cultured human biliary epithelial cells induced the accumulation of PI3K at the host cell-parasite interface and resulted in the activation of PI3K in infected cells. Frabin also was recruited to the host cell-parasite interface, a process inhibited by two PI3K inhibitors, wortmannin and LY294002. The cellular expression of either a dominant negative mutant of PI3K (PI3K-Deltap85) or functionally deficient mutants of frabin inhibited C. parvum-induced Cdc42 accumulation at the host cell-parasite interface. Moreover, LY294002 abolished C. parvum-induced Cdc42 activation in infected cells. Inhibition of PI3K by cellular overexpression of PI3K-Deltap85 or by wortmannin or LY294002, as well as inhibition of frabin by various functionally deficient mutants, decreased C. parvum-induced actin accumulation and inhibited C. parvum cellular invasion. In contrast, the overexpression of the p85 subunit of PI3K promoted C. parvum invasion. Our data suggest that an important component of the complex process of C. parvum invasion of target epithelia results from the ability of the organism to trigger host cell PI3K/frabin signaling to activate the Cdc42 pathway, resulting in host cell actin remodeling at the host cell-parasite interface.
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Affiliation(s)
- Xian-Ming Chen
- The Center for Basic Research in Digestive Diseases, Division of Gastroenterology and Hepatology, Mayo Medical School, Clinic and Foundation, Rochester, Minnesota 55905, USA
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57
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Chen XM, Huang BQ, Splinter PL, Orth JD, Billadeau DD, McNiven MA, LaRusso NF. Cdc42 and the actin-related protein/neural Wiskott-Aldrich syndrome protein network mediate cellular invasion by Cryptosporidium parvum. Infect Immun 2004; 72:3011-21. [PMID: 15102814 PMCID: PMC387898 DOI: 10.1128/iai.72.5.3011-3021.2004] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Cryptosporidium parvum invasion of epithelial cells involves host cell membrane alterations which require a remodeling of the host cell actin cytoskeleton. In addition, an actin plaque, possibly associated with the dense-band region, forms within the host cytoplasm at the host-parasite interface. Here we show that Cdc42 and RhoA, but not Rac1, members of the Rho family of GTPases, are recruited to the host-parasite interface in an in vitro model of human biliary cryptosporidiosis. Interestingly, activation of Cdc42, but not RhoA, was detected in the infected cells. Neural Wiskott-Aldrich syndrome protein (N-WASP) and p34-Arc, actin-regulating downstream effectors of Cdc42, were also recruited to the host-parasite interface. Whereas cellular expression of a constitutively active mutant of Cdc42 promoted C. parvum invasion, overexpression of a dominant negative mutant of Cdc42, or depletion of Cdc42 mRNA by short interfering RNA-mediated gene silencing, inhibited C. parvum invasion. Expression of the WA fragment of N-WASP to block associated actin polymerization also inhibited C. parvum invasion. Moreover, inhibition of host cell Cdc42 activation by dominant negative mutation inhibited C. parvum-associated actin remodeling, membrane protrusion, and dense-band formation. In contrast, treatment of cells with a Rho inhibitor, exoenzyme C3, or cellular overexpression of dominant negative mutants of RhoA and Rac1 had no effect on C. parvum invasion. These data suggest that C. parvum invasion of target epithelia results from the organism's ability to activate a host cell Cdc42 GTPase signaling pathway to induce host cell actin remodeling at the attachment site.
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Affiliation(s)
- Xian-Ming Chen
- The Center for Basic Research in Digestive Diseases, Division of Gastroenterology and Hepatology, Mayo Medical School, Clinic and Foundation, Rochester, Minnesota 55905, USA
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58
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Deng M, Lancto CA, Abrahamsen MS. Cryptosporidium parvum regulation of human epithelial cell gene expression. Int J Parasitol 2004; 34:73-82. [PMID: 14711592 DOI: 10.1016/j.ijpara.2003.10.001] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Cryptosporidium parvum is an obligate intracellular protozoan capable of causing life-threatening diarrhoeal disease in immunocompromised individuals. Efforts to develop novel therapeutic strategies have been hampered by the lack of understanding of the pathogenesis of infection. To better understand the host response to C. parvum infection, gene expression profiles of infected human ileocecal adenocarcinoma cells were analysed by using Affymetrix oligonucleotide microarrays containing probe sets for 12,600 human genes. Statistical analysis of expression data from three independent experiments identified 223 genes whose expression was reproducibly regulated by C. parvum infection at 24 h post-inoculation (125 up-regulated and 98 down-regulated), 13 of which were validated by quantitative reverse transcriptase polymerase chain reaction analysis. This analysis revealed the consistent up-regulation of host heat-shock genes and genes for pro-inflammatory chemokines IL-8, RANTES, and SCYB5. Multiple genes for host actin and tubulin genes were up-regulated whereas genes for actin binding proteins were down-regulated, confirming previous observations of host cytoskeleton rearrangement in response to C. parvum infection. In addition, host genes associated with cell proliferation and apoptosis were differentially regulated, reflecting the complexity of host-parasite interaction. Together, this study demonstrated that C. parvum infection results in significant changes in host biochemical pathways and provides new insights into specific biological processes of infectious disease caused by an intracellular protozoan parasite.
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Affiliation(s)
- Mingqi Deng
- Department of Veterinary PathoBiology, College of Veterinary Medicine, University of Minnesota, 1988 Fitch Avenue, St Paul, MN 55108, USA
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59
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Abstract
Intracellular parasites use various strategies to invade cells and to subvert cellular signaling pathways and, thus, to gain a foothold against host defenses. Efficient cell entry, ability to exploit intracellular niches, and persistence make these parasites treacherous pathogens. Most intracellular parasites gain entry via host-mediated processes, but apicomplexans use a system of adhesion-based motility called "gliding" to actively penetrate host cells. Actin polymerization-dependent motility facilitates parasite migration across cellular barriers, enables dissemination within tissues, and powers invasion of host cells. Efficient invasion has brought widespread success to this group, which includes Toxoplasma, Plasmodium, and Cryptosporidium.
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Affiliation(s)
- L D Sibley
- Department of Molecular Microbiology, Center for Infectious Diseases, Washington University School of Medicine, St. Louis, MO 63110, USA.
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60
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Huang BQ, Chen XM, LaRusso NF. CRYPTOSPORIDIUM PARVUM ATTACHMENT TO AND INTERNALIZATION BY HUMAN BILIARY EPITHELIA IN VITRO: A MORPHOLOGIC STUDY. J Parasitol 2004; 90:212-21. [PMID: 15165040 DOI: 10.1645/ge-3204] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
To explore the mechanisms by which Cryptosporidium parvum infects epithelial cells, we performed a detailed morphological study by serial electron microscopy to assess attachment to and internalization of biliary epithelial cells by C. parvum in an in vitro model of human biliary cryptosporidiosis. When C. parvum sporozoites initially attach to the host cell membrane, the rhoptry of the sporozoite extends to the attachment site; both micronemes and dense granules are recruited to the apical complex region of the attached parasite. During internalization, numerous vacuoles covered by the parasite's plasma membrane are formed and cluster together to establish a preparasitophorous vacuole. This preparasitophorous vacuole comes in contact with host cell membrane to form a host cell-parasite membrane interface, beneath which an electron-dense band begins to appear within the host cell cytoplasm. Simultaneously, host cells display membrane protrusion along the edge of the host cell-parasite membrane interface, resulting in the formation of a mature parasitophorous vacuole that completely covers the parasite. During internalization, vacuole-like structures appear in the apical complex region of the attached sporozoite, which bud out into host cells. A tunnel directly connecting the parasite to the host cell cytoplasm forms during internalization and remains when the parasite is totally internalized. Immunoelectron microscopy showed that sporozoite-associated proteins were localized along the dense band and at the parasitophorous vacuole membrane. These morphological observations provide evidence that secretion of parasite apical organelles and protrusion of host cell membrane play an important role in the attachment and internalization of host epithelial cells by C. parvum.
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Affiliation(s)
- Bing Q Huang
- The Center for Basic Research in Digestive Diseases, Division of Gastroenterology and Hepatology, Mayo Medical School, Clinic and Foundation, 200 First Street, Southwest, Rochester, Minnesota 55905, USA
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61
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Buret AG, Chin AC, Scott KGE. Infection of human and bovine epithelial cells with Cryptosporidium andersoni induces apoptosis and disrupts tight junctional ZO-1: effects of epidermal growth factor. Int J Parasitol 2003; 33:1363-71. [PMID: 14527519 DOI: 10.1016/s0020-7519(03)00138-3] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The effects of Cryptosporidium andersoni on human or bovine epithelia are poorly defined. Epidermal growth factor inhibits colonisation of the gastrointestinal epithelium with bacteria and the enteric protozoan parasite Giardia lamblia. This study characterised whether C. andersoni infects human or bovine epithelial cells in vitro, assessed its impact on apoptosis and tight junctional Zonula-Occludens-1, and determined whether these effects may be altered by epidermal growth factor. Monolayers of human colonic CaCo(2) cells, SCBN (non-malignant small intestinal epithelial cells), and Madin Darby bovine kidney epithelial cell lines (MDBK and NBL-1) were grown to confluency in Dulbecco's Modified Eagle Medium. Monolayers were assigned to one of three experimental groups-(1) control: exposed to culture medium alone; (2) untreated: exposed to 10(3) live C. andersoni oocysts or (3) epidermal growth factor-treated: apically pre-treated with recombinant human epidermal growth factor and then exposed to Cryptosporidium. Oocyst viability, infection with Cryptosporidium, apoptosis, and integrity of tight junctional Zonula-Occludens-1 were assessed. In addition, live Cryptosporidium oocysts were incubated with epidermal growth factor to assess whether epidermal growth factor had cryptosporicidial activity. Cryptosporidium andersoni oocysts infected all human and bovine monolayers, increased nuclear fragmentation, and disrupted Zonula-Occludens-1. Apical epidermal growth factor significantly reduced infection with C. andersoni in all cell lines and inhibited the Cryptosporidium-induced apoptosis and disruption of Zonula-Occludens-1. Epidermal growth factor did not affect oocyst viability.
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Affiliation(s)
- Andre G Buret
- Department of Biological Sciences, 2500 University Dr N.W. Calgary, (AB) T2N 1N4 Calgary, Canada.
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62
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Abstract
Cryptosporidium parvum is an intracellular protozoan parasite that causes a severe diarrheal illness of unclear etiology. Also unclear is the fate of the host cell upon parasite egress. We show in an MDCK cell model that the host cell is killed upon parasite egress; this death is necrotic, rather than apoptotic, in nature.
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Affiliation(s)
- David A Elliott
- Department of Pathology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21287, USA
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63
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Chen XM, Huang BQ, Splinter PL, Cao H, Zhu G, McNiven MA, LaRusso NF. Cryptosporidium parvum invasion of biliary epithelia requires host cell tyrosine phosphorylation of cortactin via c-Src. Gastroenterology 2003; 125:216-28. [PMID: 12851885 DOI: 10.1016/s0016-5085(03)00662-0] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
BACKGROUND & AIMS Cryptosporidium parvum invasion of epithelia requires polymerization of host cell actin at the attachment site. We analyzed the role of host cell c-Src, a cytoskeleton-associated protein tyrosine kinase, in C. parvum invasion of biliary epithelia. METHODS In vitro models of biliary cryptosporidiosis using a human biliary epithelial cell line were used to assay the role of c-Src signaling pathway in C. parvum invasion. RESULTS c-Src and cortactin, an actin-binding protein and a substrate for c-Src, were recruited to the parasite-host cell interface during C. parvum invasion. Tyrosine phosphorylation of cortactin in infected cells was also detected. Inhibition of host cell c-Src significantly blocked C. parvum -induced accumulation and tyrosine phosphorylation of cortactin and actin polymerization at the attachment sites, thereby inhibiting C. parvum invasion of biliary epithelial cells. A triple mutation of tyrosine of cortactin in the epithelia also diminished C. parvum invasion. In addition, proteins originating from the parasite were detected within infected cells at the parasite-host cell interface. Antiserum against C. parvum membrane proteins blocked accumulation of c-Src and cortactin and significantly decreased C. parvum invasion. No accumulation of the endocytosis-related proteins, dynamin 2 and clathrin, was found at the parasite-host cell interface; also, inhibition of dynamin 2 did not block C. parvum invasion. CONCLUSIONS C. parvum invasion of biliary epithelial cells requires host cell tyrosine phosphorylation of cortactin by a c-Src-mediated signaling pathway to induce actin polymerization at the attachment site, a process associated with microbial secretion but independent of host cell endocytosis.
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Affiliation(s)
- Xian-Ming Chen
- Center for Basic Research in Digestive Diseases, Division of Gastroenterology and Hepatology, Mayo Medical School, Clinic and Foundation, Rochester, Minnesota 55905, USA
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64
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Abstract
Actin-based motility (ABM) is employed by spotted fever group (SFG) rickettsiae, such as Rickettsia rickettsii, to promote cell-to-cell spread. Time-lapse video microscopy revealed that ABM is not strictly confined to SFG rickettsiae as typhus group R. typhi moved at approximately the same rate as R. rickettsii (approximately 4 micro m/min), but in a highly erratic fashion. A number of common behaviors were observed between ABM of R. typhi and R. rickettsii, such as entrance into plasma membrane protrusions, formation of new actin tails only on the old surface of newly formed daughter cells, and quick (within 15 sec) reassembly of the actin tail to the opposite pole upon contact with cellular structures that impede forward movement. This last behavior suggests that the rickettsial protein(s) required for ABM is uniformly localized to both poles of the bacterium and possibly throughout the rickettsial surface. Functional roles in rickettsial ABM for neuronal Wiskott-Aldrich syndrome protein (N-WASP) and the actin-related protein (Arp)2/3 complex, critical regulators of ABM of other pathogens, have not been established. Domains of N-WASP that have characterized inhibitory effects on N-WASP or Arp2/3 complex function were expressed in HeLa cells infected with R. rickettsii. Shigella flexneri-infected cells were used as a control. When ectopically expressed, the VCA domain of N-WASP (VCA) acts as a dominant/negative with respect to Arp2/3 complex function and N-WASP missing VCA (DeltaVCA) acts as a dominant/negative form of N-WASP. Expression of VCA or DeltaVCA severely inhibited S. flexneri ABM (no Shigella motility observed in the majority of expressing cells) while only moderately inhibiting ABM of R. rickettsii (approximately 35% decrease in the rate of ABM). In addition, ectopically expressed full-length GFP-N-WASP was recruited by S. flexneri but not R. rickettsii, and Arp3 was detected by indirect immunofluorescence in S. flexneri actin tails but not within R. rickettsii actin tails. Collectively, these data suggest that rickettsial ABM is independent of N-WASP and Arp2/3 complex function.
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Affiliation(s)
- Robert A Heinzen
- Department of Molecular Biology, University of Wyoming, Laramie 82071-3944, USA.
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65
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Abstract
Pathogenic microbes subvert normal host-cell processes to create a specialized niche, which enhances their survival. A common and recurring target of pathogens is the host cell's cytoskeleton, which is utilized by these microbes for purposes that include attachment, entry into cells, movement within and between cells, vacuole formation and remodelling, and avoidance of phagocytosis. Our increased understanding of these processes in recent years has not only contributed to a greater comprehension of the molecular causes of infectious diseases, but has also revealed fundamental insights into normal functions of the cytoskeleton. From the use of bacterial toxins to investigate Rho family GTPases to in vitro studies of actin polymerization using Listeria and Shigella, the study of pathogenesis has provided important tools to probe cytoskeletal function.
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Affiliation(s)
- Samantha Gruenheid
- Biotechnology Laboratory, University of British Columbia, Vancouver, Canada V6T 1Z3
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66
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Harlander RS, Way M, Ren Q, Howe D, Grieshaber SS, Heinzen RA. Effects of ectopically expressed neuronal Wiskott-Aldrich syndrome protein domains on Rickettsia rickettsii actin-based motility. Infect Immun 2003; 71:1551-6. [PMID: 12595475 PMCID: PMC148882 DOI: 10.1128/iai.71.3.1551-1556.2003] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Neuronal Wiskott-Aldrich syndrome protein (N-WASP) and the actin-related protein 2/3 (Arp2/3) complex have emerged as critical host proteins that regulate pathogen actin-based motility. Actin tail formation and motility in Listeria monocytogenes require the Arp2/3 complex but bypasses N-WASP signaling. Motility of Shigella flexneri and vaccinia virus requires both N-WASP and the Arp2/3 complex. Functional roles for these cytoskeletal regulatory proteins in actin-based motility of Rickettsia rickettsii have not been established. In this study, functional domains of N-WASP tagged with green fluorescent protein that have characterized effects on Shigella and vaccinia virus actin-based motility were ectopically expressed in HeLa cells infected with R. rickettsii to assess their effects on rickettsial motility. S. flexneri-infected cells were used as a control. Expressed N-WASP domains did not localize to R. rickettsii or their actin tails. Expression of N-WASP missing the VCA domain (for "verprolin homology, cofilin homology, and acidic domains"), which acts as a dominant-negative form of N-WASP, completely inhibited actin-based motility of S. flexneri while only moderately inhibiting motility of R. rickettsii. Similarly, expression of the VCA domain, which acts as a dominant-negative with respect to Arp2/3 complex function, severely inhibited actin-based motility of S. flexneri (no motility observed in the majority of expressing cells) but only moderately inhibited R. rickettsii motility. These results, taken together with the differential effects on motility observed upon expression of other N-WASP domains, suggest that actin-based motility of R. rickettsii is independent of N-WASP and the Arp2/3 complex.
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Affiliation(s)
- Ronald S Harlander
- Department of Molecular Biology, University of Wyoming, Laramie, Wyoming 82071-3944, USA
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67
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Magdalena J, Millard TH, Etienne-Manneville S, Launay S, Warwick HK, Machesky LM. Involvement of the Arp2/3 complex and Scar2 in Golgi polarity in scratch wound models. Mol Biol Cell 2003; 14:670-84. [PMID: 12589062 PMCID: PMC150000 DOI: 10.1091/mbc.e02-06-0345] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Cell motility and cell polarity are essential for morphogenesis, immune system function, and tissue repair. Many animal cells move by crawling, and one main driving force for movement is derived from the coordinated assembly and disassembly of actin filaments. As tissue culture cells migrate to close a scratch wound, this directional extension is accompanied by Golgi apparatus reorientation, to face the leading wound edge, giving the motile cell inherent polarity aligned relative to the wound edge and to the direction of cell migration. Cellular proteins essential for actin polymerization downstream of Rho family GTPases include the Arp2/3 complex as an actin nucleator and members of the Wiskott-Aldrich Syndrome protein (WASP) family as activators of the Arp2/3 complex. We therefore analyzed the involvement of the Arp2/3 complex and WASP-family proteins in in vitro wound healing assays using NIH 3T3 fibroblasts and astrocytes. In NIH 3T3 cells, we found that actin and Arp2/3 complex contributed to cell polarity establishment. Moreover, overexpression of N-terminal fragments of Scar2 (but not N-WASP or Scar1 or Scar3) interfere with NIH 3T3 Golgi polarization but not with cell migration. In contrast, actin, Arp2/3, and WASP-family proteins did not appear to be involved in Golgi polarization in astrocytes. Our results thus indicate that the requirement for Golgi polarity establishment is cell-type specific. Furthermore, in NIH 3T3 cells, Scar2 and the Arp2/3 complex appear to be involved in the establishment and maintenance of Golgi polarity during directed migration.
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Affiliation(s)
- Juana Magdalena
- School of Biosciences, University of Birmingham, Edgbaston, United Kingdom
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Carabeo RA, Grieshaber SS, Fischer E, Hackstadt T. Chlamydia trachomatis induces remodeling of the actin cytoskeleton during attachment and entry into HeLa cells. Infect Immun 2002; 70:3793-803. [PMID: 12065523 PMCID: PMC128046 DOI: 10.1128/iai.70.7.3793-3803.2002] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
To elucidate the host cell machinery utilized by Chlamydia trachomatis to invade epithelial cells, we examined the role of the actin cytoskeleton in the internalization of chlamydial elementary bodies (EBs). Treatment of HeLa cells with cytochalasin D markedly inhibited the internalization of C. trachomatis serovar L2 and D EBs. Association of EBs with HeLa cells induced localized actin polymerization at the site of attachment, as visualized by either phalloidin staining of fixed cells or the active recruitment of GFP-actin in viable infected cells. The recruitment of actin to the specific site of attachment was accompanied by dramatic changes in the morphology of cell surface microvilli. Ultrastructural studies revealed a transient microvillar hypertrophy that was dependent upon C. trachomatis attachment, mediated by structural components on the EBs, and cytochalasin D sensitive. In addition, a mutant CHO cell line that does not support entry of C. trachomatis serovar L2 did not display such microvillar hypertrophy following exposure to L2 EBs, which is in contrast to infection with serovar D, to which it is susceptible. We propose that C. trachomatis entry is facilitated by an active actin remodeling process that is induced by the attachment of this pathogen, resulting in distinct microvillar reorganization throughout the cell surface and the formation of a pedestal-like structure at the immediate site of attachment and entry.
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Affiliation(s)
- Reynaldo A Carabeo
- Host-Parasite Interactions Section, Laboratory of Intracellular Parasites, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana 59840, USA
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Affiliation(s)
- Xian-Ming Chen
- Center for Basic Research in Digestive Diseases, Mayo Medical School, Clinic, and Foundation, Rochester, Minn 55905, USA
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Abstract
Infections of the human gastrointestinal tract with enteric pathogens are among the leading causes of disease, suffering, and death worldwide. Enteric pathogens are ingested from contaminated food and water and pass through the entire gastrointestinal tract during establishment in the host and subsequent shedding and spread to new hosts. Nonetheless, each pathogen exploits a unique niche within the intestinal tract and has developed unique strategies to interact with different host cells and functions. The most important and prevalent infections of the small intestine are caused by diarrheagenic Escherichia coli, particularly enterotoxigenic and enteropathogenic E. coli, rotavirus, Giardia lamblia, and Cryptosporidium parvum. This review focuses on recent insights into the pathogenesis of infections with these pathogens and host defenses against them.
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Affiliation(s)
- Lars Eckmann
- Department of Medicine, University of California, San Diego, La Jolla, California 92093, USA.
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Abstract
The Apicomplexa are a phylum of diverse obligate intracellular parasites including Plasmodium spp., the cause of malaria; Toxoplasma gondii and Cryptosporidium parvum, opportunistic pathogens of immunocompromised individuals; and Eimeria spp. and Theileria spp., parasites of considerable agricultural importance. These protozoan parasites share distinctive morphological features, cytoskeletal organization, and modes of replication, motility, and invasion. This review summarizes our current understanding of the cytoskeletal elements, the properties of cytoskeletal proteins, and the role of the cytoskeleton in polarity, motility, invasion, and replication. We discuss the unusual properties of actin and myosin in the Apicomplexa, the highly stereotyped microtubule populations in apicomplexans, and a network of recently discovered novel intermediate filament-like elements in these parasites.
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Affiliation(s)
- Naomi S Morrissette
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
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