scholarly journals ARP2/3-Mediated Actin Nucleation Associated With Symbiosome Membrane Is Essential for the Development of Symbiosomes in Infected Cells of Medicago truncatula Root Nodules

2015 ◽  
Vol 28 (5) ◽  
pp. 605-614 ◽  
Author(s):  
Aleksandr Gavrin ◽  
Veerle Jansen ◽  
Sergey Ivanov ◽  
Ton Bisseling ◽  
Elena Fedorova
Keyword(s):  
Actin Cytoskeleton ◽  
Host Cell ◽  
Medicago Truncatula ◽  
Root Nodules ◽  
Nitrogen Fixing ◽  
Actin Networks ◽  
Cell Plasma ◽  
Membrane Compartments ◽  
Infected Cells

The nitrogen-fixing rhizobia in the symbiotic infected cells of root nodules are kept in membrane compartments derived from the host cell plasma membrane, forming what are known as symbiosomes. These are maintained as individual units, with mature symbiosomes having a specific radial position in the host cell cytoplasm. The mechanisms that adapt the host cell architecture to accommodate intracellular bacteria are not clear. The intracellular organization of any cell depends heavily on the actin cytoskeleton. Dynamic rearrangement of the actin cytoskeleton is crucial for cytoplasm organization and intracellular trafficking of vesicles and organelles. A key component of the actin cytoskeleton rearrangement is the ARP2/3 complex, which nucleates new actin filaments and forms branched actin networks. To clarify the role of the ARP2/3 complex in the development of infected cells and symbiosomes, we analyzed the pattern of actin microfilaments and the functional role of ARP3 in Medicago truncatula root nodules. In infected cells, ARP3 protein and actin were spatially associated with maturing symbiosomes. Partial ARP3 silencing causes defects in symbiosome development; in particular, ARP3 silencing disrupts the final differentiation steps in functional maturation into nitrogen-fixing units.

scholarly journals Host Cell Plasma Membrane Phosphatidylserine Regulates the Assembly and Budding of Ebola Virus

2015 ◽  
Vol 89 (18) ◽  
pp. 9440-9453 ◽  
Author(s):  
Emmanuel Adu-Gyamfi ◽  
Kristen A. Johnson ◽  
Mark E. Fraser ◽  
Jordan L. Scott ◽  
Smita P. Soni ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Host Cell ◽  
Human Cell ◽  
Mammalian Cells ◽  
Matrix Protein ◽  
Ebola Virus ◽  
Cell Plasma Membrane ◽  
Replication Process ◽  
Cell Plasma

ABSTRACTLipid-enveloped viruses replicate and bud from the host cell where they acquire their lipid coat. Ebola virus, which buds from the plasma membrane of the host cell, causes viral hemorrhagic fever and has a high fatality rate. To date, little has been known about how budding and egress of Ebola virus are mediated at the plasma membrane. We have found that the lipid phosphatidylserine (PS) regulates the assembly of Ebola virus matrix protein VP40. VP40 binds PS-containing membranes with nanomolar affinity, and binding of PS regulates VP40 localization and oligomerization on the plasma membrane inner leaflet. Further, alteration of PS levels in mammalian cells inhibits assembly and egress of VP40. Notably, interactions of VP40 with the plasma membrane induced exposure of PS on the outer leaflet of the plasma membrane at sites of egress, whereas PS is typically found only on the inner leaflet. Taking the data together, we present a model accounting for the role of plasma membrane PS in assembly of Ebola virus-like particles.IMPORTANCEThe lipid-enveloped Ebola virus causes severe infection with a high mortality rate and currently lacks FDA-approved therapeutics or vaccines. Ebola virus harbors just seven genes in its genome, and there is a critical requirement for acquisition of its lipid envelope from the plasma membrane of the human cell that it infects during the replication process. There is, however, a dearth of information available on the required contents of this envelope for egress and subsequent attachment and entry. Here we demonstrate that plasma membrane phosphatidylserine is critical for Ebola virus budding from the host cell plasma membrane. This report, to our knowledge, is the first to highlight the role of lipids in human cell membranes in the Ebola virus replication cycle and draws a clear link between selective binding and transport of a lipid across the membrane of the human cell and use of that lipid for subsequent viral entry.

scholarly journals Lipidomics Issues on Human Positive ssRNA Virus Infection: An Update

Metabolites ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 356 ◽  
Author(s):  
David Balgoma ◽  
Luis Gil-de-Gómez ◽  
Olimpio Montero
Keyword(s):  
Lipid Metabolism ◽  
Virus Infection ◽  
Host Cell ◽  
Viral Infections ◽  
Virus Entry ◽  
Pathogenic Mechanisms ◽  
Cell Lipid ◽  
Ssrna Virus ◽  
Infected Cells

The pathogenic mechanisms underlying the Biology and Biochemistry of viral infections are known to depend on the lipid metabolism of infected cells. From a lipidomics viewpoint, there are a variety of mechanisms involving virus infection that encompass virus entry, the disturbance of host cell lipid metabolism, and the role played by diverse lipids in regard to the infection effectiveness. All these aspects have currently been tackled separately as independent issues and focused on the function of proteins. Here, we review the role of cholesterol and other lipids in ssRNA+ infection.

scholarly journals The Signal Peptide of the Medicago truncatula Modular Nodulin MtNOD25 Operates as an Address Label for the Specific Targeting of Proteins to Nitrogen-Fixing Symbiosomes

2009 ◽  
Vol 22 (1) ◽  
pp. 63-72 ◽  
Author(s):  
Natalija Hohnjec ◽  
Frauke Lenz ◽  
Vera Fehlberg ◽  
Martin F. Vieweg ◽  
Markus C. Baier ◽  
...  
Keyword(s):  
Medicago Truncatula ◽  
Signal Peptide ◽  
Root Nodules ◽  
Cellular Level ◽  
Specific Element ◽  
Model Legume ◽  
Specific Targeting ◽  
C Terminus ◽  
Organ Specific ◽  
Infected Cells

The nodule-specific MtNOD25 gene of the model legume Medicago truncatula encodes a modular nodulin composed of different repetitive modules flanked by distinct N- and C-termini. Although similarities are low with respect to all repetitive modules, both the N-terminal signal peptide (SP) and the C-terminus are highly conserved in modular nodulins from different legumes. On the cellular level, MtNOD25 is only transcribed in the infected cells of root nodules, and this activation is mediated by a 299-bp minimal promoter containing an organ-specific element. By expressing mGFP6 translational fusions in transgenic nodules, we show that MtNOD25 proteins are exclusively translocated to the symbiosomes of infected cells. This specific targeting only requires an N-terminal MtNOD25 SP that is highly conserved across a family of legume-specific symbiosome proteins. Our finding sheds light on one possible mechanism for the delivery of host proteins to the symbiosomes of infected root nodule cells and, in addition, defines a short molecular address label of only 24 amino acids whose N-terminal presence is sufficient to translocate proteins across the peribacteroid membrane.

scholarly journals Loss of the nodule-specific cysteine rich peptide, NCR169, abolishes symbiotic nitrogen fixation in the Medicago truncatula dnf7 mutant

2015 ◽  
Vol 112 (49) ◽  
pp. 15232-15237 ◽  
Author(s):  
Beatrix Horváth ◽  
Ágota Domonkos ◽  
Attila Kereszt ◽  
Attila Szűcs ◽  
Edit Ábrahám ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Medicago Truncatula ◽  
Symbiotic Nitrogen Fixation ◽  
Root Nodules ◽  
Nitrogen Fixing ◽  
In Planta ◽  
Functional Roles ◽  
Absolute Requirement ◽  
Cell Layers

Host compatible rhizobia induce the formation of legume root nodules, symbiotic organs within which intracellular bacteria are present in plant-derived membrane compartments termed symbiosomes. In Medicago truncatula nodules, the Sinorhizobium microsymbionts undergo an irreversible differentiation process leading to the development of elongated polyploid noncultivable nitrogen fixing bacteroids that convert atmospheric dinitrogen into ammonia. This terminal differentiation is directed by the host plant and involves hundreds of nodule specific cysteine-rich peptides (NCRs). Except for certain in vitro activities of cationic peptides, the functional roles of individual NCR peptides in planta are not known. In this study, we demonstrate that the inability of M. truncatula dnf7 mutants to fix nitrogen is due to inactivation of a single NCR peptide, NCR169. In the absence of NCR169, bacterial differentiation was impaired and was associated with early senescence of the symbiotic cells. Introduction of the NCR169 gene into the dnf7-2/NCR169 deletion mutant restored symbiotic nitrogen fixation. Replacement of any of the cysteine residues in the NCR169 peptide with serine rendered it incapable of complementation, demonstrating an absolute requirement for all cysteines in planta. NCR169 was induced in the cell layers in which bacteroid elongation was most pronounced, and high expression persisted throughout the nitrogen-fixing nodule zone. Our results provide evidence for an essential role of NCR169 in the differentiation and persistence of nitrogen fixing bacteroids in M. truncatula.

Septins as key regulators of actin based processes in bacterial infection

2011 ◽  
Vol 392 (8-9) ◽  
pp. 831-835 ◽  
Author(s):  
Serge Mostowy ◽  
Pascale Cossart
Keyword(s):  
Actin Cytoskeleton ◽  
Bacterial Infection ◽  
Host Cell ◽  
Complete Picture ◽  
Intracellular Movement ◽  
Infection Processes ◽  
Precise Role

Abstract Many pathogens have evolved a variety of mechanisms to exploit the host-cell actin cytoskeleton during infection, either to enter into cells or to move within cells. These events have been investigated and documented in detail. Yet, a complete picture of the molecules and mechanisms regulating entry and intracellular movement remains to be established. Here we present a series of studies revealing that in addition to actin rearrangements the host cell also employs septins, a relatively newly characterized component of the cell cyto-skeleton, to regulate bacterial entry and restrict the dissemination of cytosolic bacteria. The challenge now is to decipher the precise role of septins during actin rearrangements and how these different cytoskeleton components orchestrate infection processes.

scholarly journals Iron Transport across Symbiotic Membranes of Nitrogen-Fixing Legumes

2021 ◽  
Vol 22 (1) ◽  
pp. 432
Author(s):  
David A. Day ◽  
Penelope M. C. Smith
Keyword(s):  
Iron Transport ◽  
Root Nodules ◽  
Nitrogen Fixing ◽  
High Demand ◽  
Symbiosome Membrane ◽  
Essential Nutrient ◽  
Infected Cells ◽  
Very High

Iron is an essential nutrient for the legume-rhizobia symbiosis and nitrogen-fixing bacteroids within root nodules of legumes have a very high demand for the metal. Within the infected cells of nodules, the bacteroids are surrounded by a plant membrane to form an organelle-like structure called the symbiosome. In this review, we focus on how iron is transported across the symbiosome membrane and accessed by the bacteroids.

scholarly journals Evidence for Host Cells as the Major Contributor of Lipids in the Intravacuolar Network of Toxoplasma-Infected Cells

2011 ◽  
Vol 10 (8) ◽  
pp. 1095-1099 ◽  
Author(s):  
Carolina E. Caffaro ◽  
John C. Boothroyd
Keyword(s):  
Host Cell ◽  
Fluorescence Recovery After Photobleaching ◽  
Parasitophorous Vacuole ◽  
Dense Granule ◽  
Host Cells ◽  
Cell Plasma Membrane ◽  
Content Type ◽  
Cell Plasma ◽  
Continuous Stream ◽  
Infected Cells

ABSTRACT The intracellular parasite Toxoplasma gondii develops inside a parasitophorous vacuole (PV) that derives from the host cell plasma membrane during invasion. Previous electron micrograph images have shown that the membrane of this vacuole undergoes an extraordinary remodeling with an extensive network of thin tubules and vesicles, the intravacuolar network (IVN), which fills the lumen of the PV. While dense granule proteins, secreted during and after invasion, are the main factors for the organization and tubulation of the network, little is known about the source of lipids used for this remodeling. By selectively labeling host cell or parasite membranes, we uncovered evidence that strongly supports the host cell as the primary, if not exclusive, source of lipids for parasite IVN remodeling. Fluorescence recovery after photobleaching (FRAP) microscopy experiments revealed that lipids are surprisingly dynamic within the parasitophorous vacuole and are continuously exchanged or replenished by the host cell. The results presented here suggest a new model for development of the parasitophorous vacuole whereby the host provides a continuous stream of lipids to support the growth and maturation of the PVM and IVN.

scholarly journals Cortactin signalling and dynamic actin networks

2004 ◽  
Vol 382 (1) ◽  
pp. 13-25 ◽  
Author(s):  
Roger J. DALY
Keyword(s):  
Tyrosine Kinase ◽  
Actin Cytoskeleton ◽  
Current Knowledge ◽  
Actin Binding ◽  
Related Protein ◽  
Protein Targets ◽  
Actin Networks ◽  
Multiple Protein ◽  
Initial Characterization

Cortactin was first identified over a decade ago, and its initial characterization as both an F-actin binding protein and v-Src substrate suggested that it was likely to be a key regulator of actin rearrangements in response to tyrosine kinase signalling. The recent discovery that cortactin binds and activates the actin related protein (Arp)2/3 complex, and thus regulates the formation of branched actin networks, together with the identification of multiple protein targets of the cortactin SH3 domain, have revealed diverse cellular roles for this protein. This article reviews current knowledge regarding the role of cortactin in signalling to the actin cytoskeleton in the context of these developments.

Secretion by Toxoplasma gondii of an antigen that appears to become associated with the parasitophorous vacuole membrane upon invasion of the host cell

1987 ◽  
Vol 88 (2) ◽  
pp. 231-239
Author(s):  
I. Kimata ◽  
K. Tanabe
Keyword(s):  
Toxoplasma Gondii ◽  
Host Cell ◽  
Anterior Part ◽  
Parasitophorous Vacuole ◽  
Host Cells ◽  
Immunoperoxidase Staining ◽  
Cell Plasma ◽  
Sds Page ◽  
Infected Cells ◽  
Triton X

Monoclonal antibodies against Toxoplasma gondii were prepared to characterize antigens of the parasite. Immunoperoxidase staining of parasites fixed with paraformaldehyde and glutaraldehyde (PFAGA) followed by Triton X-100 treatment showed that the antibody of clone I-63 recognized an antigen located in the anterior part of the parasite. When analysed by SDS-PAGE and immunoblotting, the antigen migrated in a 66 × 10(3) Mr region. The parasite antigen diminished greatly in parasites after invasion of host cells, but reappeared around a time when intracellular T. gondii multiplied. Immunodetection on PFAGA-fixed T. gondii-infected cells, whose membranes were permeabilized by freeze-thawing in the presence of 5% glycerol, demonstrated that, immediately after parasite invasion, the I-63 antibody-reactive antigen appeared to become associated with the parasitophorous vacuole (PV) membrane, that had been formed mainly by invagination of the host-cell plasma membrane so as to surround an invading parasite. The antigen remained associated with the PV membrane for some time, but disappeared later when the PV increased in size after the parasites had multiplied several times. These results were strengthened by immunoelectron microscopic observations: the antigen that had been localized at the anterior part of the parasite before invasion appeared in an area of the host cell cytoplasm around the tips of penetrating parasites and, thereafter, extended throughout the surface of the PV membrane when parasites completed invasion. Thus, it appears that the I-63-reactive antigen is secreted by T. gondii upon invasion of the host cell and becomes associated with the PV membrane shortly after invasion.

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