Protein Phosphatase 2A Modulates AKT-Mediated Macrophage Polarization in Adipocyte-Induced Inflammation

Obesity and type 2 diabetes mellitus (T2DM) are associated with chronic low-grade inflammation that sustains insulin resistance and metabolic dysfunction. Adipose tissue, through the secretion of adipokines and cytokines, plays a central role in shaping macrophage polarization and maintenance of an inflammatory microenvironment. While kinase-mediated signaling such as PI3K-AKT has been extensively studied, the contribution of phosphatases, particularly protein phosphatase 2A (PP2A), to macrophage polarization remains poorly defined. In this study, RAW264.7 macrophages exposed to inflammatory adipocyte-conditioned medium exhibited altered AKT isoform expression, including upregulation of AKT2 and downregulation of AKT1, along with activation of the PI3K, mTORC1/S6K pathway and suppression of protein phosphatase 2A (PP2A) activity, collectively promoting M1 pro-inflammatory polarization. To further elucidate the molecular mechanism, we performed molecular docking and 100 ns molecular dynamics simulations of both unphosphorylated AKT and ATP-bound (phosphorylated) AKT interacting with PP2A. The simulations revealed that phosphorylated AKT has higher binding affinity and greater structural stability with PP2A, facilitated by persistent hydrogen bonds with the regulatory and scaffolding subunits, suggesting a natural self-limiting mechanism that maintains the phosphorylation-dephosphorylation balance. We hypothesise that the experimentally observed reduction in PP2A levels in macrophages exposed to inflammatory adipocyte signals may impair this regulatory loop, favouring sustained pro-inflammatory signaling. These integrated experimental and computational findings highlight PP2A as a critical negative regulator of AKT-driven macrophage activation and suggest that therapeutic strategies aimed at restoring PP2A activity could prevent chronic inflammation in obesity and T2DM and could serve as a potential molecular target for mitigating metabolic inflammation.