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Updated: Mar 30, 2026
Three-dimensional Confocal Analysis of Microglia/macrophage Markers of Polarization in Experimental Brain Injury
Published on: September 4, 2013
TRAM1 Promotes Microglia M1 Polarization
Hanxiang Wang1, Chun Liu2, Ming Han1
1Jiangsu Province Key Laboratory for Inflammation and Molecular Drug Target, Medical College of Nantong University, Nantong, Jiangsu Province, 226001, China.
Abstract:
Microglia, the major immune cells of the central nervous system (CNS), can be driven to adopt M1 and M2 phenotypes. Recently, the distinct functions of M1 and M2 microglia have been intensively studied. M1-activation microglia are pro-inflammatory and may contribute to the development of several CSN disorders, while M2-activation microglia are anti-inflammatory and may promote tissue reconstruction. TRAM1 is a protein involved in translocation of nascent polypeptides and functions as a sorting adaptor of TLR4. Here, we found that TRAM1 plays an important role in microglia M1 polarization. Our results showed that the expression of TRAM1 is highly induced in LPS/interferon (IFN)-γ-stimulated BV2 cells and primary microglia cells. Flag-TRAM1 transfection, but not Flag-GFP used as a control, significantly enhanced M1 polarization by strongly increasing expression of M1 makers, such as IL-6, IL-1β, iNOS, and so on. Silence of TRAM1 effectively inhibited LPS/IFN-γ-induced expression of M1-related genes in BV2 cells. In addition, TRAM1 was found to cooperate with TLR4 to induce an M1 genetic program in Flag-TRAM1-transfected and LPS/IFN-γ-induced BV2 cells. TRAM1 is essential for LPS/IFN-γ induced expressions of adapter molecule (IRAK1, phosphorylation of TBK1, and IRF3) of TLR4. TRAM1 is also essential for phosphorylation of IκB and P65 and for P65-NF-kB translocation to nucleus. Overall, our findings showed that TRAM1 could promote microglia M1 polarization.
Insights
Translocase of the outer membrane 1 (TRAM1) promotes pro-inflammatory M1 microglia polarization. TRAM1 is essential for Toll-like receptor 4 (TLR4) signaling, driving M1 gene expression in the central nervous system.
Area of Science:
- Neuroimmunology
- Cellular Biology
- Molecular Mechanisms
Background:
- Microglia are central nervous system immune cells with M1 (pro-inflammatory) and M2 (anti-inflammatory) phenotypes.
- M1 microglia are implicated in central nervous system (CNS) disorders, while M2 microglia aid tissue repair.
- Translocase of the outer membrane 1 (TRAM1) is a protein involved in polypeptide translocation and Toll-like receptor 4 (TLR4) sorting.
Purpose of the Study:
- To investigate the role of TRAM1 in microglia polarization, specifically M1 polarization.
- To elucidate the molecular mechanisms by which TRAM1 influences M1 microglia activation.
Main Methods:
- Stimulation of BV2 and primary microglia cells with LPS/interferon-gamma (IFN-γ).
- Overexpression of Flag-TRAM1 and control Flag-GFP.
- Gene silencing of TRAM1.
- Analysis of M1 marker gene expression (IL-6, IL-1β, iNOS).
- Assessment of TLR4 signaling pathway components (IRAK1, TBK1, IRF3, IκB, P65).
Main Results:
- TRAM1 expression is upregulated in activated microglia.
- TRAM1 overexpression enhances M1 polarization and M1 marker gene expression.
- TRAM1 silencing inhibits LPS/IFN-γ-induced M1 gene expression.
- TRAM1 cooperates with TLR4 to induce M1 polarization.
- TRAM1 is crucial for TLR4 pathway activation, including IRAK1, TBK1, IRF3, IκB, and P65 signaling.
Conclusions:
- TRAM1 plays a significant role in promoting microglia M1 polarization.
- TRAM1 acts as a key mediator in the TLR4 signaling pathway, driving pro-inflammatory responses in microglia.
- TRAM1 is a potential therapeutic target for CNS disorders associated with M1 microglia activation.
