Fig. 4

PBS FLNA mutations disrupt binding to integrin. a PyMol 3D protein standard cartoon of wildtype IgFLNA repeats 19 (magenta), 20 (green), and 21 (blue) showing the auto-inhibitory IgFLNA20 β-strand A on the β-strand C/D face of IgFLNA21. Shown in red are C2160 and G2236, the locations of the two FLNA residues in Ig20 and Ig21 mutated in PBS (PDB code 2J3S). The position of the IgFLNA20 β-strand A residue I2144 is shown in black; although it has not been reported mutated in humans, the I2144E mutation has been shown to lead to increased FLNA-ITGβ binding. The FLNA PBS mutation p.A1448V in Ig13 is not shown. b Pulldown assay showing that p.C2160R and p.G2236E mutations enhance binding to ITGβ1 similarly to engineered positive controls p.I2144E and p.ΔIg20. In contrast, p.A1448V binds ITGβ1 similar to WT. CHO cells were transfected with full length FLNA and bound to ITGβ1 tails on beads. c qPCR across adult human tissues shows ITGB1 expression is highest in small intestines but also strong bladder expression. ITGB1 expression normalized to GAPDH and relative to brain. d IHC from pediatric normal human bladder shows plasma membrane smooth muscle expression of ITGβ1