Membrane-Associated Guanylate Kinase Inverted 2 Regulates the Organization of Podocyte Actin Cytoskeleton through Its Interaction with α-Actinin-4 and Synaptopodin

Key Points The loss of membrane-associated guanylate kinase inverted 2 (MAGI-2) induces actin cytoskeleton reorganization in mice. MAGI-2, α -actinin-4, and synaptopodin form a complex in vitro . Regulating MAGI-2 has the potential to suppress foot process effacement and is a promising target for podocyte damage. Background Podocytes form interdigitating foot processes connected by the slit diaphragm (SD), which serves as a size-selective and charge-selective barrier essential for glomerular filtration. In kidney diseases, it is known that podocyte injury leads to the reorganization of the actin cytoskeleton, resulting in foot process effacement, which contributes to proteinuria and the progression of the disease. However, the detailed mechanisms underlying the regulation of actin cytoskeleton reorganization remain unclear. This study aims to elucidate the role of the scaffolding protein membrane-associated guanylate kinase inverted 2 (MAGI-2) in actin cytoskeleton regulation and to explore its potential as a novel therapeutic target. Methods MAGI-2 was specifically knocked out in podocytes, and the localization changes of the actin cytoskeleton were observed in mice. In addition, immunoprecipitation experiments were performed in cultured cells to identify the binding domains of MAGI-2 with α -actinin-4 and synaptopodin (Synpo), key components of the actin cytoskeleton, and their colocalization changes were analyzed. Results In the absence of MAGI-2 in podocytes, actin bundles normally located in the center of the foot processes were found to shift toward the basement membrane, indicating that MAGI-2 contributes to cytoskeletal reorganization. Immunoprecipitation revealed that MAGI-2 forms a complex with Synpo and α -actinin-4, and co-expression in cultured podocytes induced a relocalization of the actin cytoskeleton toward cell-cell contact. These findings suggest that MAGI-2, in addition to its previously known role as a scaffolding protein of the SD, directly interacts with actin-associated proteins and plays a critical role in the reorganization of the podocyte cytoskeleton. Conclusions MAGI-2 binds to Synpo and α -actinin-4, regulating actin filament localization and contributing to cytoskeletal reorganization in podocytes. These findings uncover a new molecular link between SD components and the actin cytoskeleton, offering insights into mechanisms of podocyte injury.