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The modulation of macrophage activation by tyrosine phosphorylation
Illya Tietzel1, David M Mosser
1Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA.
Abstract:
Activated macrophages are a critical component of our antimicrobial armamentarium. Unfortunately, the lipid mediators and free radicals that these cells produce are not only toxic to potential pathogens, but also to the host. Thus the modulation of these activities can mitigate an overzealous immune response and thereby prevent host cell injury. Two families of receptor tyrosine kinases (RTK) in macrophages, the RON/STK and the Tyro3 families of protein kinases, will be examined in this review with an emphasis on their roles in modulating the effector functions of activated macrophages. Both families of receptors are capable of down-regulating the inflammatory response of macrophages to lipopolysaccharide, and both families of RTK's are structurally related. An analysis of the intracellular domains of RON/STK and Tyro3 reveal a common multi-substrate binding site, which can recruit common signaling molecules such as growth factor receptor bound 2 (Grb2) and phosphatidylinositol 3-kinase (PI3-K). The observations relating to a modulation of macrophage effector mechanisms by these receptors open unexplored avenues for the development of pharmacological immunomodulators with the potential to exploit elements of this common pathway.
Insights
Receptor tyrosine kinases (RTKs) like RON/STK and Tyro3 regulate macrophage immune responses. Targeting their common signaling pathway offers a novel approach for developing immunomodulators to prevent host injury during infection.
Area of Science:
- Immunology
- Cell Signaling
- Molecular Biology
Background:
- Activated macrophages are crucial for fighting pathogens but can harm the host.
- Lipid mediators and free radicals produced by macrophages can cause host cell injury.
- Modulating macrophage activity is key to preventing excessive immune responses.
Purpose of the Study:
- To review the roles of RON/STK and Tyro3 receptor tyrosine kinases (RTKs) in modulating activated macrophage functions.
- To explore the potential of these RTKs as targets for pharmacological immunomodulators.
Main Methods:
- Review of existing literature on RON/STK and Tyro3 receptor tyrosine kinases.
- Analysis of the structural and signaling similarities between these RTK families.
- Examination of their role in down-regulating inflammatory responses in macrophages.
Main Results:
- Both RON/STK and Tyro3 RTKs down-regulate macrophage inflammatory responses to lipopolysaccharide.
- These RTK families are structurally related and share common intracellular signaling molecules.
- A common multi-substrate binding site recruits signaling molecules like Grb2 and PI3-K.
Conclusions:
- The RON/STK and Tyro3 RTK families represent promising targets for immunomodulatory drug development.
- Exploiting their common signaling pathway could lead to novel therapies for inflammatory conditions.
- Targeting these pathways may mitigate host injury caused by overzealous immune responses.