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Intracellular vs extracellular recognition of pathogens--common concepts in mammals and flies
Stephen E Girardin1, Philippe J Sansonetti, Dana J Philpott
1Pathogénie Microbienne Moléculaire and Immunité Innée et Signalisation, Institut Pasteur, 28 rue du Dr Roux, 75724 Cédex 15, Paris, France.
Abstract:
There are common themes in innate immune defense systems across the animal and plant kingdoms. Pathogen recognition is commonly based on the identification of microbial molecular patterns by defined receptors and the subsequent activation of signaling pathways that initiate a defense response to fend off the invading microorganism. The existence of mammalian Toll-like receptors (TLRs) and the recent identification of two mammalian nucleotide-binding site leucine-rich repeat (NBS-LRR) proteins (NOD1 and NOD2) as intracellular sensors of bacterial products bring new insights into the possibility of extracellular versus intracellular pathogen recognition and signal transduction depending on the nature of the infection. The homology between TLRs and the Toll system in Drosophila suggests that conserved defense mechanisms are likely to be shared by diverse organisms.
Insights
Innate immunity shares common themes across animals and plants, utilizing pattern recognition receptors to detect pathogens. Mammalian Toll-like receptors (TLRs) and NBS-LRR proteins reveal conserved extracellular and intracellular defense mechanisms.
Area of Science:
- Innate immunity
- Comparative immunology
- Molecular biology
Background:
- Innate immune defense systems exhibit conserved mechanisms across diverse kingdoms, including animals and plants.
- Pathogen recognition relies on identifying microbial molecular patterns via specific receptors, triggering signaling pathways for defense.
- Mammalian Toll-like receptors (TLRs) and nucleotide-binding site leucine-rich repeat (NBS-LRR) proteins (NOD1, NOD2) offer insights into pathogen sensing.
Purpose of the Study:
- To explore conserved themes in innate immune defense systems.
- To highlight the roles of Toll-like receptors (TLRs) and NBS-LRR proteins in pathogen recognition.
- To investigate the implications of extracellular versus intracellular pathogen recognition.
Main Methods:
- Comparative analysis of innate immune pathways in animals and plants.
- Review of literature on Toll-like receptors (TLRs) and NBS-LRR proteins.
- Examination of signaling cascades involved in pathogen detection.
Main Results:
- Common themes in pathogen recognition and defense signaling exist across animal and plant kingdoms.
- Toll-like receptors (TLRs) in mammals show homology to the Toll system in Drosophila, indicating conserved mechanisms.
- NOD1 and NOD2 function as intracellular sensors of bacterial products, distinguishing between extracellular and intracellular threats.
Conclusions:
- Conserved defense mechanisms are likely shared across diverse organisms, from plants to mammals.
- The study of TLRs and NBS-LRR proteins provides crucial insights into the evolution and function of innate immunity.
- Understanding these conserved pathways is vital for developing novel therapeutic strategies against infectious diseases.