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Screening Bioactive Nanoparticles in Phagocytic Immune Cells for Inhibitors of Toll-like Receptor Signaling
Published on: July 26, 2017
Innate Immune Recognition, Integrated Stress Response, Infection, and Tumorigenesis
Klara Kubelkova1, Vanda Bostik2, Lokesh Joshi3
1Department of Molecular Pathology and Biology, Faculty of Military Health Sciences, University of Defence, 500 01 Hradec Kralove, Czech Republic.
Abstract:
Engagement of PRRs in recognition of PAMPs or DAMPs is one of the processes that initiates cellular stress. These sensors are involved in signaling pathways leading to induction of innate immune processes. Signaling initiated by PRRs is associated with the activation of MyD88-dependent signaling pathways and myddosome formation. MyD88 downstream signaling depends upon the context of signaling initiation, the cell (sub)type and the microenvironment of signal initiation. Recognition of PAMPs or DAMPs through PRRs activates the cellular autonomous defence mechanism, which orchestrates the cell responses to resolve specific insults at the single cell level. In general, stressed endoplasmic reticulum is directly linked with the induction of autophagy and initiation of mitochondrial stress. These processes are regulated by the release of Ca2+ from ER stores accepted by mitochondria, which respond through membrane depolarization and the production of reactive oxygen species generating signals leading to inflammasome activation. In parallel, signaling from PRRs initiates the accumulation of misfolded or inappropriately post-translationally modified proteins in the ER and triggers a group of conserved emergency rescue pathways known as unfolded protein response. The cell-autonomous effector mechanisms have evolutionarily ancient roots and were gradually specialized for the defence of specific cell (sub)types. All of these processes are common to the innate immune recognition of microbial pathogens and tumorigenesis as well. PRRs are active in both cases. Downstream are activated signaling pathways initiated by myddosomes, translated by the cellular autonomous defence mechanism, and finalized by inflammasomes.
Insights
Pattern recognition receptors (PRRs) initiate cellular stress responses by activating innate immunity pathways. These pathways involve MyD88-dependent signaling, inflammasomes, and cell-autonomous defenses, crucial in both pathogen defense and tumorigenesis.
Area of Science:
- Immunology
- Cellular Biology
- Molecular Biology
Background:
- Pattern recognition receptors (PRRs) detect pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs), initiating cellular stress and innate immune responses.
- Signaling cascades involving MyD88-dependent pathways and myddosome formation are activated upon PRR engagement.
- Cellular stress, including endoplasmic reticulum stress and mitochondrial dysfunction, triggers autophagy and the unfolded protein response.
Purpose of the Study:
- To elucidate the intricate signaling networks initiated by PRRs in response to PAMPs/DAMPs.
- To understand the role of MyD88-dependent pathways and inflammasome activation in cellular defense mechanisms.
- To highlight the commonalities in PRR-mediated signaling during microbial infections and tumorigenesis.
Main Methods:
- Analysis of PRR signaling pathways.
- Investigation of MyD88-dependent signaling and myddosome formation.
- Examination of endoplasmic reticulum stress, autophagy, and inflammasome activation.
Main Results:
- PRR engagement triggers MyD88-dependent signaling and myddosome formation, initiating innate immune processes.
- Cellular autonomous defense mechanisms orchestrate responses to insults, involving ER stress, autophagy, and mitochondrial signaling.
- Inflammasome activation is a downstream consequence of these interconnected signaling events.
Conclusions:
- PRR signaling is central to cellular stress responses and innate immunity, involving conserved pathways like MyD88 and inflammasomes.
- Cell-autonomous defense mechanisms are critical for resolving cellular insults and are activated by ER and mitochondrial stress.
- The elucidated signaling pathways are relevant to both host defense against pathogens and the development of cancer.
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