The Role of Plastin in Bone, Cartilage, and Related Diseases.

The plastin family (PLS1, PLS2, PLS3) comprises highly conserved actin-binding proteins (ABPs) that regulate cytoskeletal dynamics by cross-linking actin microfilaments and play key roles in bone and cartilage development, homeostasis, and disease. PLS1 primarily stabilizes tight actin bundles in epithelial brush-border microvilli and has also been reported to support osteoblast differentiation via regulating intracellular Ca2+ homeostasis. In bone, PLS3 mutations lead to X-linked osteoporosis through mechanisms involving the inhibition of the WNT pathway, activation of TH17 cell differentiation, and disorders of osteogenesis mediated by the neutrophil extracellular trap (NET) pathway. Meanwhile, PLS2 promotes osteoclast sealing ring assembly and drives bone resorption via Ser-5/Ser-7 phosphorylation. In cartilage, PLS3 is highly expressed on the surface layer of osteoarthritis (OA) patients, with expression levels positively correlating with degeneration severity, possibly involved in chondrocyte hypertrophy in response to mechanical loading. Pathologically, PLS3 deficiency directly causes early-onset osteoporosis and increased fracture risk, while PLS2 plays a dual role in cancer metastasis and inflammation. Targeting plastin, such as inhibiting PLS2 phosphorylation or supplementing PLS3 mRNA, offers potential new strategies for treating hyperresorption and hereditary bone diseases.