Abstract
PGLYRP1/Tag-7/PGRP-S is one of mammalian peptidoglycan recognition proteins (PGRPs). Here, we demonstrate that human recombinant PGLYRP1/Tag-7/PGRP-S potentiates the response of murine macrophage-like ANA-1 cells and human macrophages to facultative intracellular pathogen Listeria monocytogenes. PGLYRP1/Tag-7/PGRP-S binds to the surface of L. monocytogenes and other bacterial cells but has no effect on their growth in culture. While PGLYRP1/Tag-7/PGRP-S treatment modestly enhanced phagocytosis of bacteria by ANA-1 cells, the intracellular survival of PGLYRP1/Tag-7/PGRP-S treated L. monocytogenes was strongly inhibited 2 h after internalization. PGLYRP1/Tag-7/PGRP-S treatment of bacteria boosted oxidative burst induction and increased the level of proinflammatory cytokine IL-6 produced by ANA-1, however, these effects happened too late to be responsible for decreased intracellular survival of bacteria. Our results thus suggest that PGLYRP1/Tag-7/PGRP-S acts as a molecular sensor for detection of L. monocytogenes infection of mammalian cells that leads to increased killing through a mechanism(s) that remains to be defined.
Highlights
Mammalian immunity can be subdivided into innate immunity and adaptive, or specific, immunity (Rodrıguez et al, 2012)
PGLYRP1 ortholog peptidoglycan recognition proteins (PGRPs)-SA plays a significant role in the recognition of Gram-positive bacteria by the innate immune system
We demonstrated that recombinant human PGLYRP1 protects macrophages and the macrophage-derived cell line ANA-1 from L. monocytogenes infection via enhancement of intracellular mechanisms of bacterial killing, rather than by direct bactericidal action
Summary
Mammalian immunity can be subdivided into innate immunity and adaptive, or specific, immunity (Rodrıguez et al, 2012). The innate immune system is a more ancient part of the host defense against infection. Innate immunity uses various response mechanisms, such as recognition of pathogens and killing by dedicated cells (e.g., macrophages engulf bacteria and produce several substances for their killing, including reactive oxygen species), and presentation of specific parts of the pathogen to adaptive immunity (Medzhitov et al, 1997). Innate immunity recognizes characteristic conserved structures of microorganisms which are absent from the host and are called pathogen-associated molecular patterns (PAMPs) (Janeway, 1989). Peptidoglycan, which is an essential and specific component of almost all bacteria (Rogers et al, 1980), serves as a target recognized by innate immunity
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