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Proteomic Analysis of Human Macrophage Polarization Under a Low Oxygen Environment
Published on: January 7, 2019
AFM-IR probing the influence of polarization on the expression of proteins within single macrophages
Zhibin Liu1, Huarong Zeng, Kunqi Xu
1CAS Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China. huarongzeng@mail.sic.ac.cn wangd@mail.sic.ac.cn.
Abstract:
Macrophages are essential in innate immunity and are involved in a variety of biological functions. Due to high plasticity, macrophages are polarized in different phenotypes depending on different microenvironments to perform specific functions. Although many studies have focused on macrophage polarization, few have explored the polarization characteristics of macrophages at the subcellular level, even at nanoscale resolution. Here, we utilize AFM-based infrared spectroscopy (AFM-IR) to investigate the influence of an inducer on the expressed proteins of M1/M2 macrophages (induced by LPS and IL-13, respectively). The results from AFM-IR combined with principal component analysis revealed that the characteristic proteins within M1 contain about 35% antiparallel β-sheets (due to the high expression of TNF-α), while the proteins within M2 are made up of approximately 38.8% α-helices. The corresponding nanoscale chemical mapping demonstrates a remarkably heterogeneous distribution of expressed proteins inside single macrophages. Beside the biochemical properties, the biomechanical properties of macrophages were found to be softened in response to the polarization process.
Insights
This study reveals nanoscale protein differences in M1 and M2 macrophages using AFM-IR. Macrophage polarization alters both protein composition and mechanical properties at the subcellular level.
Area of Science:
- Cellular Biology
- Immunology
- Nanotechnology
Background:
- Macrophages are crucial immune cells with high plasticity, enabling polarization into distinct phenotypes (M1/M2) based on microenvironmental cues.
- While macrophage polarization is well-studied, nanoscale subcellular protein expression and biomechanical changes remain underexplored.
Purpose of the Study:
- To investigate the nanoscale biochemical and biomechanical properties of M1 and M2 polarized macrophages.
- To explore the influence of inducers like LPS and IL-13 on macrophage protein expression at the subcellular level.
Main Methods:
- Atomic Force Microscopy-based Infrared Spectroscopy (AFM-IR) was employed to analyze protein secondary structures (β-sheets, α-helices) within single macrophages.
- Principal Component Analysis (PCA) was used in conjunction with AFM-IR data for detailed chemical mapping.
- Biomechanical properties were assessed to understand changes related to polarization.
Main Results:
- AFM-IR revealed distinct protein compositions: M1 macrophages showed ~35% antiparallel β-sheets (linked to TNF-α), while M2 macrophages exhibited ~38.8% α-helices.
- Nanoscale chemical mapping demonstrated heterogeneous protein distribution within individual macrophages.
- Macrophage polarization was associated with significant softening of their biomechanical properties.
Conclusions:
- AFM-IR provides nanoscale resolution for characterizing macrophage polarization at the subcellular protein level.
- Polarization induces significant changes in both the biochemical (protein structure) and biomechanical properties of macrophages.
- This study highlights the heterogeneity of protein expression within single macrophages and offers new insights into immune cell plasticity.
