ABSTRACT Cyclase-associated protein 2 (CAP2) is a conserved actin-binding protein that promotes actin filament (F-actin) turnover by disassembling ADF/cofilin-decorated filaments, supporting F-actin remodeling in differentiating cells and tissues. In the ocular lens, the actin cytoskeleton is crucial for maintaining tissue biomechanical properties during fiber cell maturation. To assess the role of CAP2 in the lens, we examined lens-specific CAP2 knockout (CAP2cKO) mice at cellular and tissue levels. CAP2cKO lenses were normal in size, shape and transparency but exhibited increased stiffness under compression and enhanced recovery after load removal. Although total actin and F-actin levels were unchanged, immunofluorescence revealed higher levels for tropomodulin 1 (Tmod1, F-actin pointed-end capping), tropomyosin isoform 3.5 (Tpm3.5, F-actin stabilizing) and T-plastin (also known as PLS3; F-actin bundling) in F-actin-rich membrane protrusions of mature fibers, whereas that for α-actinin-1 (F-actin cross-linking) was reduced. These findings suggest that CAP2 loss disrupts F-actin remodeling, indirectly promoting filament stabilization through Tpm3.5 binding, Tmod1 capping and T-plastin bundling. Consequently, F-actin networks become stiffer and more resilient, altering lens biomechanics. This study provides the first evidence that CAP2 maintains cell biomechanical properties in a non-muscle tissue through influencing the composition of actin cytoskeleton networks
Cheheltani et al. (Fri,) studied this question.