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Mac-1 Regulates IL-13 Activity in Macrophages by Directly Interacting with IL-13Rα1
Chunzhang Cao1, Juanjuan Zhao1, Emily K Doughty2
1From the Departments of Physiology and.
Abstract:
Mac-1 exhibits a unique inhibitory activity toward IL-13-induced JAK/STAT activation and thereby regulates macrophage to foam cell transformation. However, the underlying molecular mechanism is unknown. In this study, we report the identification of IL-13Rα1, a component of the IL-13 receptor (IL-13R), as a novel ligand of integrin Mac-1, using a co-evolution-based algorithm. Biochemical analyses demonstrated that recombinant IL-13Rα1 binds Mac-1 in a purified system and supports Mac-1-mediated cell adhesion. Co-immunoprecipitation experiments revealed that endogenous Mac-1 forms a complex with IL-13Rα1 in solution, and confocal fluorescence microscopy demonstrated that these two receptors co-localize with each other on the surface of macrophages. Moreover, we found that genetic inactivation of Mac-1 promotes IL-13-induced JAK/STAT activation in macrophages, resulting in enhanced polarization along the alternative activation pathway. Importantly, we observed that Mac-1(-/-) macrophages exhibit increased expression of foam cell differentiation markers including 15-lipoxygenase and lectin-type oxidized LDL receptor-1 both in vitro and in vivo. Indeed, we found that Mac-1(-/-)LDLR(-/-) mice develop significantly more foam cells than control LDLR(-/-) mice, using an in vivo model of foam cell formation. Together, our data establish for the first time a molecular mechanism by which Mac-1 regulates the signaling activity of IL-13 in macrophages. This newly identified IL-13Rα1/Mac-1-dependent pathway may offer novel targets for therapeutic intervention in the future.
Insights
Integrin Mac-1 binds IL-13Rα1, inhibiting macrophage foam cell formation. This discovery reveals a new Mac-1-dependent pathway regulating IL-13 signaling, offering potential therapeutic targets.
Area of Science:
- Immunology
- Cell Biology
- Molecular Medicine
Background:
- Mac-1 (integrin αMβ2) regulates macrophage function, including foam cell transformation.
- The precise molecular mechanism by which Mac-1 inhibits IL-13-induced signaling remains elusive.
Purpose of the Study:
- To identify the molecular mechanism underlying Mac-1's inhibitory effect on IL-13 signaling and macrophage foam cell transformation.
- To characterize the interaction between Mac-1 and components of the IL-13 receptor (IL-13R).
Main Methods:
- Co-evolution-based algorithm for ligand identification.
- Biochemical assays (recombinant protein binding, co-immunoprecipitation).
- Confocal fluorescence microscopy for receptor co-localization.
- Macrophage functional assays (JAK/STAT activation, foam cell differentiation markers).
- In vivo studies using Mac-1 knockout and LDLR knockout mice.
Main Results:
- IL-13Rα1 identified as a novel ligand for integrin Mac-1.
- Mac-1 and IL-13Rα1 interact directly and co-localize on macrophage surfaces.
- Genetic inactivation of Mac-1 enhances IL-13-induced JAK/STAT activation and alternative macrophage polarization.
- Mac-1 deficiency leads to increased foam cell differentiation markers in vitro and in vivo.
- Mac-1(-/-)LDLR(-/-) mice exhibit significantly increased foam cell formation.
Conclusions:
- This study establishes IL-13Rα1 as a direct binding partner of Mac-1, elucidating a novel molecular mechanism for Mac-1's regulation of IL-13 signaling in macrophages.
- The identified IL-13Rα1/Mac-1 pathway is crucial for controlling macrophage polarization and foam cell transformation, presenting potential therapeutic targets for atherosclerosis and related diseases.
