E11(Mouse)

Ezrin Regulates Rac1 Activity via Its N-Terminal FERM Domain in Glomerular Podocytes

Ezrin is a key cytoskeletal protein in glomerular podocytes, forming complexes with NHERF2 and podocalyxin. While podocalyxin is essential for renal filtration, the specific physiological role of ezrin remains unclear. Hatano et al. utilized the immortalized podocyte cell line E11, which abundantly expresses ezrin (Fig. 1a), to investigate its function via siRNA-mediated knockdown.

Effective ezrin depletion did not alter total podocalyxin expression (Fig. 1b, Total lysate) or its membrane localization, as confirmed by cell surface biotinylation (Fig. 1b, Cell surface). However, ezrin knockdown significantly reduced Rac1 activity without affecting RhoA activity (Fig. 1c). To dissect the structural determinants of this effect, they transfected E11 cells with various ezrin mutants. While RhoA activity remained unchanged across all constructs (Fig. 2a), Rac1 activity was significantly increased by constitutively active ezrin (T567D) and the isolated N-terminal FERM domain (N term-ezrin), and decreased by the inactive mutant (T567A) (Fig. 2b). Full-length ezrin (FL) and a C-terminal truncation lacking the actin-binding domain (ΔCt) did not significantly alter Rac1 activity (Fig. 2b). These findings indicate that ezrin regulates podocyte Rac1 activity through its N-terminal FERM domain and T567 phosphorylation, independent of podocalyxin membrane localization.