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Functional Characterization of Regulatory Macrophages That Inhibit Graft-reactive Immunity
Published on: June 7, 2017
Disruption of CDK5 regulatory subunit 1, p35, limits immunosuppressive M2 macrophages while maintaining functional M1
Juliana R Zampieri1, Sung Hee Choi2,3, Jay T Myers2
1Faculdade Israelita de Ciências da Saúde Albert Einstein Hospital Israelita Albert Einstein, São Paulo, Brazil.
Introduction:
Macrophage polarization into M1 or M2 phenotypes is a complex process influenced by various factors. However, existing literature and ongoing research support the view that Cyclin-Dependent Kinase 5 (CDK5) may play an important role in this process. CDK5 is a protein kinase that requires association with regulatory, co-activating proteins, p35 (CDK5R1) or p39 (CDK5R2), for functional activation.
Purpose:
This study investigated the role of the p35 protein in regulating M1 and M2 polarization.
Methods:
We compared bone marrow derived macrophages from wild type (WT) and p35 knockout (KO) mice under both M1 (IFNγ + LPS) and M2 (IL4) conditions, differentiated with M-CSF or GM-CSF. The expression of surface markers (CD86, CD206), enzyme expression (Arginase-1 and iNOS), metabolism and antigen process and presentation were compared.
Results:
While p35 had modest effect on phenotype during M1 or M2 polarization, p35 expression was important for Arginase1 induction after M2 polarization. The absence of p35 significantly increased glycolysis during M1 polarization, while it also enhanced mitochondrial oxidative phosphorylation in the context of M2 polarization. While p35 was important for antigen processing by M0 and M2, M1 were able to maintain capacity to process antigen albeit with a reduction due to decreased stability of peptide: MHC II complex.
Conclusion:
While loss of p35 resulted in minor changes in phenotype, there were decreases in ARG-1 production and STAT3 phosphorylation, increased metabolism, and dramatically reduced antigen processing by M0, M1 or M2. The absence of p35 enhanced antigen uptake, but it had no effect on degradation of antigen, suggesting an inability to produce peptide: MHC II complexes in the absence of p35 in M0 and M2. In contrast, p35-deficient M1 maintained an ability to rapidly produce peptide: MHC II complexes but showed a reduction in the stability of these complexes on the surface. Our findings reveal a crucial role for p35 in regulating macrophage metabolism and antigen function, with implications for the development of novel therapeutic strategies.
Insights
The p35 protein is crucial for macrophage metabolism and antigen processing, impacting M1 and M2 polarization. Its absence alters glycolysis, oxidative phosphorylation, and antigen presentation, suggesting therapeutic potential.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Macrophage polarization into M1 and M2 phenotypes is critical for immune responses.
- Cyclin-Dependent Kinase 5 (CDK5) is implicated in cellular processes, requiring regulatory subunits like p35 for activation.
Purpose of the Study:
- To investigate the specific role of the p35 protein in regulating macrophage polarization to M1 and M2 phenotypes.
- To understand how p35 influences macrophage metabolism and antigen processing during polarization.
Main Methods:
- Comparison of bone marrow-derived macrophages from wild-type and p35 knockout mice.
- Assessment of M1 (IFNγ + LPS) and M2 (IL4) polarization markers, including surface markers (CD86, CD206) and enzyme expression (Arginase-1, iNOS).
- Analysis of macrophage metabolism, antigen processing, and presentation capabilities.
Main Results:
- p35 deficiency led to decreased Arginase-1 production and STAT3 phosphorylation, particularly after M2 polarization.
- Absence of p35 increased glycolysis in M1 polarization and enhanced mitochondrial oxidative phosphorylation in M2 polarization.
- p35 was essential for efficient antigen processing and peptide: MHC II complex stability, especially in M0 and M2 macrophages, though M1 macrophages showed reduced complex stability.
Conclusions:
- The p35 protein plays a vital role in regulating macrophage metabolism and antigen processing functions.
- Loss of p35 significantly impairs antigen presentation capacity, with distinct effects on M1, M2, and naive M0 macrophages.
- These findings highlight p35 as a potential therapeutic target for modulating immune responses.
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