Intracellular invasion by Orientia tsutsugamushi is mediated by integrin signaling and actin cytoskeleton rearrangements. 2010

Bon-A Cho, and Nam-Hyuk Cho, and Seung-Yong Seong, and Myung-Sik Choi, and Ik-Sang Kim
Department of Microbiology and Immunology, Seoul National University College of Medicine, Jongno-Gu, 28 Yongond-Dong, Jongno-Gu, Seoul 110-799, Republic of Korea.

Orientia tsutsugamushi, the causative agent of scrub typhus, is an obligate intracellular pathogen. Previously, we reported that the 56-kDa type-specific antigen (TSA56), a major outer membrane protein of O. tsutsugamushi, binds to fibronectin and facilitates bacterial entry into the host cell, potentially via an interaction with integrins. Here, we demonstrated that O. tsutsugamushi colocalizes with integrin alpha 5 beta 1 and activates integrin signaling effectors, including focal adhesion kinase, Src kinase, and RhoA GTPase, and also recruits signaling adaptors, such as talin and paxillin, to the site of infection. Inhibition of protein tyrosine kinases or RhoA reduced intracellular invasion. We also observed substantial actin reorganization and membrane protrusions at the sites of infection of nonphagocytic host cells. Finally, we identified a region in the extracellular domain of TSA56 that binds to fibronectin. A peptide containing this region was able to significantly reduce bacterial invasion. Taken together, these results clearly indicate that O. tsutsugamushi exploits integrin-mediated signaling and the actin cytoskeleton for invasion of eukaryotic host cells.

UI MeSH Term Description Entries
D011485 Protein Binding The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments. Plasma Protein Binding Capacity,Binding, Protein
D002460 Cell Line Established cell cultures that have the potential to propagate indefinitely. Cell Lines,Line, Cell,Lines, Cell
D003599 Cytoskeleton The network of filaments, tubules, and interconnecting filamentous bridges which give shape, structure, and organization to the cytoplasm. Cytoplasmic Filaments,Cytoskeletal Filaments,Microtrabecular Lattice,Cytoplasmic Filament,Cytoskeletal Filament,Cytoskeletons,Filament, Cytoplasmic,Filament, Cytoskeletal,Filaments, Cytoplasmic,Filaments, Cytoskeletal,Lattice, Microtrabecular,Lattices, Microtrabecular,Microtrabecular Lattices
D004705 Endocytosis Cellular uptake of extracellular materials within membrane-limited vacuoles or microvesicles. ENDOSOMES play a central role in endocytosis. Endocytoses
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D000942 Antigens, Bacterial Substances elaborated by bacteria that have antigenic activity. Bacterial Antigen,Bacterial Antigens,Antigen, Bacterial
D012285 Orientia tsutsugamushi A gram-negative, rod-shaped to coccoid bacterium. It is the etiologic agent of SCRUB TYPHUS in humans and is transmitted by mites from rodent reservoirs. Rickettsia tsutsugamushi
D015398 Signal Transduction The intracellular transfer of information (biological activation/inhibition) through a signal pathway. In each signal transduction system, an activation/inhibition signal from a biologically active molecule (hormone, neurotransmitter) is mediated via the coupling of a receptor/enzyme to a second messenger system or to an ion channel. Signal transduction plays an important role in activating cellular functions, cell differentiation, and cell proliferation. Examples of signal transduction systems are the GAMMA-AMINOBUTYRIC ACID-postsynaptic receptor-calcium ion channel system, the receptor-mediated T-cell activation pathway, and the receptor-mediated activation of phospholipases. Those coupled to membrane depolarization or intracellular release of calcium include the receptor-mediated activation of cytotoxic functions in granulocytes and the synaptic potentiation of protein kinase activation. Some signal transduction pathways may be part of larger signal transduction pathways; for example, protein kinase activation is part of the platelet activation signal pathway. Cell Signaling,Receptor-Mediated Signal Transduction,Signal Pathways,Receptor Mediated Signal Transduction,Signal Transduction Pathways,Signal Transduction Systems,Pathway, Signal,Pathway, Signal Transduction,Pathways, Signal,Pathways, Signal Transduction,Receptor-Mediated Signal Transductions,Signal Pathway,Signal Transduction Pathway,Signal Transduction System,Signal Transduction, Receptor-Mediated,Signal Transductions,Signal Transductions, Receptor-Mediated,System, Signal Transduction,Systems, Signal Transduction,Transduction, Signal,Transductions, Signal
D016608 Talin A 235-kDa cytoplasmic protein that is also found in platelets. It has been localized to regions of cell-substrate adhesion. It binds to INTEGRINS; VINCULIN; and ACTINS and appears to participate in generating a transmembrane connection between the extracellular matrix and the cytoskeleton. Band 2 Protein,Platelet Protein p235,Protein p235, Platelet,Protein, Band 2

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