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Results for “host interacting proteins”

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PubMed1998

Plasmodium falciparum: influence of malarial and host erythrocyte skeletal protein interactions on phosphorylation in infected erythrocytes.

Phosphorylation of components of the erythrocyte membrane skeleton has major effects on the physical properties of the membrane. Infection of red cells by the protozoan parasite Plasmodium falciparum leads to a marked increase in the level of phosphorylation of red cell protein 4.1 and the insertion into the red cell skeleton of parasite-encoded phosphoproteins, including the mature-parasite-infected erythrocyte surface antigen (MESA). Because of the tight association of MESA with protein 4.1, we set out to determine the importance of this interaction and that of other parasite-encoded skeletal-associated proteins to phosphorylation of the infected red cell membrane. Our results show that neither MESA nor protein 4.1 is required for phosphorylation of its binding partner. Further, phosphorylation of MESA and protein 4.1 occurs independently of the presence of knobs, the expression of PfHRP1, or cytoadherence phenotype. In contrast to previous studies, we were unable to detect a change in the molecular weight of protein 4.1 in erythrocytes infected with cytoadherent parasite lines. In red cells infected with parasites expressing PfHRP1 (K+), MESA and protein 4.1 are substrates for a kinase with the inhibitor profile of a casein kinase. Surprisingly, however, when we examined phosphorylation of MESA and protein 4.1 in K(-)-infected erythrocytes, we found that casein kinase I and II inhibitors had no, or greatly reduced, effectiveness, and in fact, phosphorylation of these two proteins was enhanced in some instances.

Animals↗
PubMed1990

Interaction of host cell proteins with the human T-cell leukemia virus type I transcriptional control region. II. A comprehensive map of protein-binding sites facilitates construction of a simple chimeric promoter responsive to the viral tax2 gene product.

We present a map describing the binding of cellular proteins to a 300-base pair (bp) region of the human T-cell leukemia virus type I (HTLV-I) long terminal repeat. The map accounts for nearly all of the DNase I protection reported in a previous study using crude nuclear extracts. Notable features include a complex arrangement of overlapping binding sites encompassing the 21-bp repeat elements (see accompanying paper) as well as binding sites for the transcription factors Sp1 and NF-I that significantly deviate from the previously defined consensus recognition sequences. Based on the binding results, we constructed simple chimeric promoters containing 21-bp repeat elements, Sp1-, and nuclear factor I-binding sites upstream of a TATA box. Transient transfection experiments show that these promoters are expressed in T-cells and are regulated by the viral tax2 gene product. Deletion of the Sp1 and nuclear factor I sites abolishes tax-induction, suggesting that one or both of these proteins play a role in mediating the tax-responsiveness conferred by the 21-bp repeat element.

Base Sequence↗
PubMed1985

Sheathed and unsheathed microfilarial surfaces, interactions with host serum proteins in diethylcarbamazine.

There is no question that when a high titer of antibodies specific for microfilaria (mf) surfaces is present in assays of granulocyte adherence that cell binding is greater than in normal serum. It is also well documented that complement intact serum with or without surface specific antibody permits the deposition of C3 on mf, and surface bound C3b is known to facilitate adherence by granulocytes and especially eosinophils. How diethylcarbamazine enhances cell adherence to mf surfaces directly or as mediated by specific antibody, complement or as yet untested serum components such as eosinophil granule major basic protein (MBP) remains unknown. In reviewing work which has attempted to investigate this question, it was found that there were several possible sources of inconsistencies in the reagents usually employed in the cell adherence experiments with mf and some of these may have already contributed to confusion in the interpretation of results reported to date. Firstly, eosinophils collected from individuals with high eosinophil counts appear to be more reactive than those from normal donors. Secondly, Brugia pahangi mf taken in early patent infections or from very high microfilaremic infections in cats are less reactive with granulocytes than those from more long-term infections and this may be related to the differences in surface carbohydrate composition detected among mf taken from uteri of adult females, in vitro released mf and mf collected from host tissue. Thirdly, higher levels of MBP may be present in serum from individuals with high eosinophil counts associated with filarial infection than in serum from normal controls.

Animals↗
PubMed2005

Interactions between virus proteins and host cell membranes during the viral life cycle.

The structure and function of cells are critically dependent on membranes, which not only separate the interior of the cell from its environment but also define the internal compartments. It is therefore not surprising that the major steps of the life cycle of viruses of animals and plants also depend on cellular membranes. Indeed, interactions of viral proteins with host cell membranes are important for viruses to enter into host cells, replicate their genome, and produce progeny particles. To replicate its genome, a virus first needs to cross the plasma membrane. Some viruses can also modify intracellular membranes of host cells to create a compartment in which genome replication will take place. Finally, some viruses acquire an envelope, which is derived either from the plasma membrane or an internal membrane of the host cell. This paper reviews recent findings on the interactions of viral proteins with host cell membranes during the viral life cycle.

Animals↗
PubMed2004

Heat-shock proteins and the host-pathogen interaction during bacterial infection.

Heat-shock proteins (HSPs) are expressed at high levels by bacterial pathogens during adaptation to intracellular survival. Both host and pathogen heat-shock proteins contribute to immunity by receptor-mediated activation of the innate immune response and by participation in the presentation of antigens for the adaptive immune response. Manipulation of these interactions presents a potential route to improved control of infection by vaccination or immunotherapy.

Animals↗
PubMed2004

Interaction analysis of viral cytokine-binding proteins using surface plasmon resonance.

Surface plasmon resonance (SPR) biosensors have become an increasingly popular technology for characterizing the protein-protein interactions of virus-host interactions. Various studies have exploited the versatility of SPR to probe the interaction between virus and host components, including constituents of virus particles and host cellular receptors, as well as interactions between viral proteins and host immune molecules. This chapter describes basic procedures for employing SPR to study the interaction between poxvirus proteins and host immune-signaling proteins. We also identify how this methodology may be adapted toward other applications relevant in the study of poxvirus-host interactions.

Biosensing Techniques↗
PubMed1997

Recognition of bacteriophage Qbeta plus strand RNA as a template by Qbeta replicase: role of RNA interactions mediated by ribosomal proteins S1 and host factor.

RNA-protein interactions between bacteriophage Qbeta plus strand RNA and the components of the Qbeta replicase system were studied by deletion analysis. Internal, 5'-terminal and 3'-terminal deletions were assayed for template activity with replicase in vitro. Of the two internal binding sites previously described for replicase, we found that the S-site (map position 1247 to 1346) could be deleted without any significant effect on template activity, whereas deletion of the M-site (map position 2545 to 2867) resulted in a strong inactivation and a high salt sensitivity of the residual activity. Binding complexes of the deletion mutant RNAs with the different proteins involved in Qbeta RNA replication were analysed by electron microscopy. The formation of looped complex structures, previously reported and explained as simultaneous interactions with replicase at the S and the M-site, was abolished by deleting the S-site but, surprisingly, not by deleting the M-site. The same types of complexes observed with replicase were also formed with purified protein S1 (the alpha subunit of replicase), suggesting that these internal interactions with Qbeta RNA are mediated by the S1 protein. The Qbeta host factor, a protein required for the template activity of the Qbeta plus strand, was reported earlier to form similar complexes by binding to the S and M-sites (or adjacent sites) and in addition to the 3'-end, resulting in double-looped structures. The patterns of looped complexes observed with the deletion mutant RNAs suggest that the binding of host factor might not involve the S and M-sites themselves but adjacent downstream sites. An additional internal host factor interaction near map position 2300 was detected with several mutant RNAs. Qbeta RNA molecules with 3'-truncations formed 3'-terminal loops with similar efficiency as wild-type RNA, indicating that recognition of the 3'-end by host factor is not dependent on a specific 3'-terminal base sequence.

Allolevivirus↗
PubMed2002

A geminivirus replication protein interacts with a protein kinase and a motor protein that display different expression patterns during plant development and infection.

The geminivirus protein AL1 initiates viral DNA replication, regulates its own expression, and induces plant gene transcription. To better understand how AL1 interacts with host proteins during these processes, we used yeast two-hybrid library screening and a baculovirus protein interaction system to identify plant proteins that interact with AL1. These studies identified a Ser/Thr kinase, a kinesin, and histone H3 as AL1 partners. The kinase is autophosphorylated and can phosphorylate common kinase substrates in vitro. The kinesin is phosphorylated in insect cells by a cyclin-dependent kinase. Immunostaining of Nicotiana benthamiana and Arabidopsis showed that kinase protein levels and subcellular location are regulated during plant development and geminivirus infection. By contrast, the kinesin is ubiquitous even though it is associated with the spindle apparatus in mitotic cells. Together, our results establish that AL1 interacts with host proteins involved in plant cell division and development. Possible functions of these host factors in healthy and geminivirus-infected plants are discussed.

Animals↗
PubMed2001

Functional genomics in HIV-1 virus replication: protein-protein interactions as a basis for recruiting the host cell machinery for viral propagation.

Identification and characterization of protein-protein interactions between the host cell and parasites both enhance our understanding of basic cell biology and provide insights into central processes of parasite life cycles. Research on HIV-1 has broadened our knowledge of the various molecular events involved. However, our understanding of how this virus interacts with the host cell at the level of protein-protein interaction is still limited. Through these interactions the virus is able to recruit certain cellular metabolic pathways for its replication. Here we summarize our current knowledge of protein-protein interactions between HIV-1 and host cell factors during viral replication.

Gene Expression Regulation, Viral↗
PubMed2005

NOD-LRR proteins: role in host-microbial interactions and inflammatory disease.

Nods are cytosolic proteins that contain a nucleotide-binding oligomerization domain (NOD). These proteins include key regulators of apoptosis and pathogen resistance in mammals and plants. A large number of Nods contain leucine-rich repeats (LRRs), hence referred to as NOD-LRR proteins. Genetic variation in several NOD-LRR proteins, including human Nod2, Cryopyrin, and CIITA, as well as mouse Naip5, is associated with inflammatory disease or increased susceptibility to microbial infections. Nod1, Nod2, Cryopyrin, and Ipaf have been implicated in protective immune responses against pathogens. Together with Toll-like receptors, Nod1 and Nod2 appear to play important roles in innate and acquired immunity as sensors of bacterial components. Specifically, Nod1 and Nod2 participate in the signaling events triggered by host recognition of specific motifs in bacterial peptidoglycan and, upon activation, induce the production of proinflammatory mediators. Naip5 is involved in host resistance to Legionella pneumophila through cell autonomous mechanisms, whereas CIITA plays a critical role in antigen presentation and development of antigen-specific T lymphocytes. Thus, NOD-LRR proteins appear to be involved in a diverse array of processes required for host immune reactions against pathogens.

Adaptor Proteins, Signal Transducing↗
PubMed1996

Release of malaria circumsporozoite protein into the host cell cytoplasm and interaction with ribosomes.

To date, the circumsporozoite (CS) protein has been implicated in guiding malaria sporozoites to the liver [Cerami et al., Cell 70, 1992, 1021-1033]. Here we show that shortly after invasion, P. berghei and P. yoelii sporozoites lie free in the invaded cell and release considerable amounts of CS protein into the cytoplasm. The intracytoplasmic deposition of CS protein begins during the attachment of the sporozoite to the host cell surface and reaches its peak during the first 4-6 h after invasion. Initially, the CS protein spreads over the entire cytoplasm of the infected cell where it interacts with cytosolic as well as endoplasmic reticulum-associated ribosomes. During the subsequent development of the parasites to exoerythrocytic forms, the CS protein binding becomes gradually restricted to ribosomes lining the outer membrane of the nuclear envelope of the host cell. The distribution pattern of the parasite-released CS protein in the host cell cytoplasm is independent of the permissiveness of the host cell for the development of the parasites to exoerythrocytic forms. It requires neither the host cell metabolism nor does it involve the endocytotic machinery. Recombinant P. falciparum CS protein interacts with RNAse-sensitive sites on endoplasmic reticulum-associated ribosomes as shown by microinjection and immunoelectron microscopy. The generalized interaction of the CS protein with host cell ribosomes suggests that the CS protein has an intracellular function during the hepatic phase in the life cycle of Plasmodium and may also explain the generation of a CD8+ T cell response in the course of rodent malaria infections.

Animals↗
PubMed1991

Heat shock proteins in host-parasite interactions.

For most living organisms, heat shock represents an unusual stress situation, but for parasites that are transmitted between invertebrate vectors and mammalian hosts it is a frequent physiological occurrence. Because of the extraordinary conservation of heat shock proteins (HSPs) and their potential immunogenicity, much attention has recently focused on the role of HSPs in infection and immunity. In parasites, HSPs appear to play specific functions in differentiation, in protection from the host cell's killing mechanisms, including oxygen free radicals, and even in virulence. In this article, Barbara Polla uses the example of malaria to illustrate the possible role of HSPs in host-parasite relationships.

Animals↗
PubMed2001

The search for Brachyspira outer membrane proteins that interact with the host.

Little is known about the outer membrane structure of Brachyspira hyodysenteriae and Brachyspira pilosicoli or the role of outer membrane proteins (OMPs) in host colonization and the development of disease. The isolation of outer membrane vesicles from B. hyodysenteriae has confirmed that cholesterol is a significant outer membrane constituent and that it may impart unique characteristics to the lipid bilayer structure, including a reduced density. Unique proteins that have been identified in the B. hyodysenteriae outer membrane include the variable surface proteins (Vsp) and lipoproteins such as SmpA and BmpB. While the function of these proteins remains to be determined, there is indirect evidence to suggest that they may be involved in immune evasion. These data may explain the ability of the organism to initiate chronic infection. OMPs may be responsible for the unique attachment of B. pilosicoli to colonic epithelial cells; however, the only B. pilosicoli OMPs that have been identified to date are involved in metabolism. In order to identify further B. pilosicoli OMPs we have isolated membrane vesicle fractions from porcine strain 95-1000 by osmotic lysis and isopycnic centrifugation. The fractions were free of contamination by cytoplasm and flagella and contained outer membrane. Inner membrane contamination was minimal but could not be completely excluded. An abundant 45-kDa, heat-modifiable protein was shown to have significant homology with B. hyodysenteriae Vsp, and monoclonal antibodies were produced that reacted with five B. pilosicoli-specific membrane protein epitopes. The first of these proteins to be characterized is a unique surface-exposed lipoprotein.

Animals↗
PubMed1998

Interaction of viral proteins with host cell death machinery.

In recent years, intense research has been directed towards understanding molecular mechanisms involved in viral pathogenesis. It is now known that many viruses manipulate host defense mechanisms to prevent apoptosis in order to maximize viral replication. Towards the end of their replication cycle, certain viruses direct the synthesis of proteins that induce apoptosis or cell lysis thereby facilitating viral release from the cell. The present review summarizes the current understanding of interactions between viral proteins and the host cell death machinery.

Animals↗
PubMed1996

Applications for green fluorescent protein (GFP) in the study of host-pathogen interactions.

The green fluorescent protein (GFP) from Aequorea victoria is a novel fluorescent marker that has potential use in the study of bacterial pathogenicity. To explore some of the potential applications of GFP to the study of host-parasite interactions, we constructed two GFP expression vectors suitable for different facultative intracellular bacterial pathogens. The first expression vector was tested in the enteric pathogens, Salmonella typhimurium and Yersinia pseudotuberculosis, and the second vector tested in Mycobacterium marinum (Mm). Both expression vectors were found to be stable and to direct high levels of GFP synthesis. Standard epifluorescence microscopy was used to detect all three bacterial pathogenic species during the early and late stages of infection of live mammalian cells. Mm expressing gfp was also visualized in infected animal tissues. gfp expression did not adversely affect bacterial survival, nor did it compromise entry into mammalian cells or their survival within macrophages. In addition, all three gfp-expressing bacterial pathogens could be detected and sorted in a flow cytometer, either alone or in association with epithelial cells or macrophages. Therefore, GFP not only provides a convenient tool to image pathogenic bacteria, but allows the quantitative measurement of bacterial association with mammalian cells.

Animals↗