期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 97, 期 16, 页码 8754-8761出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.97.16.8754
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资金
- NIAID NIH HHS [R01 AI030492, R37 AI030492, AI30492] Funding Source: Medline
- NIGMS NIH HHS [GM52543] Funding Source: Medline
Salmonella spp. have evolved the ability to enter into cells that are normally nonphagocytic. The internalization process is the result of a remarkable interaction between the bacteria and the host cells. Immediately on contact, Salmonella delivers a number of bacterial effector proteins into the host cell cytosol through the function of a specialized organelle termed the type III secretion system. Initially, two of the delivered proteins, SopE and SopB, stimulate the small GTP-binding proteins Cdc42 and Rac. SopE is an exchange factor for these GTPases, and SopB is an inositol polyphosphate phosphatase. Stimulation of Cdc42 and Rac leads to marked actin cytoskeleton rearrangements, which are further enhanced by SipA, a Salmonella protein also delivered into the host cell by the type III secretion system, SipA lowers the critical concentration of C-actin, stabilizes F-actin at the site of bacterial entry, and increases the bundling activity of the host-cell protein T-plastin (fimbrin). The cellular responses stimulated by Salmonella are short-lived; therefore, immediately after bacterial entry, the cell regains its normal architecture, Remarkably, this process is mediated by SptP, another target of the type III secretion system, SptP exert its function by serving as a GTPase-activating protein for Cdc42 and Rac, turning these G proteins off after their stimulation by the bacterial effecters SopE and SopB. The balanced interaction of Salmonella with host cells constitutes a remarkable example of the sophisticated nature of a pathogen/host relationship shaped by evolution through a longstanding coexistence.
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