Actin binding LIM 1 (abLIM1) negatively controls osteoclastogenesis by regulating cell migration and fusion

Actin binding LIM 1 (abLIM1) is a cytoskeletal actin-binding protein that has been implicated in interactions between actin filaments and cytoplasmic targets. Previous biochemical and cytochemical studies have shown that abLIM1 interacts and co-localizes with F-actin in the retina and muscle. However, whether abLIM1 regulates osteoclast differentiation has not yet been elucidated. In this study, we examined the role of abLIM1 in osteoclast differentiation and function. We found that abLIM1 expression was upregulated during receptor activator of nuclear factor kappa-B ligand (RANKL)-induced osteoclast differentiation, and that a novel transcript of abLIM1 was exclusively expressed in osteoclasts. Overexpression of abLIM1 in the murine monocytic cell line, RAW-D suppressed osteoclast differentiation and decreased expression of several osteoclast-marker genes. By contrast, small interfering RNA-induced knockdown of abLIM1 enhanced the formation of multinucleated osteoclasts and markedly increased the expression of the osteoclast-marker genes. Mechanistically, abLIM1 regulated the localization of tubulin, migration, and fusion in osteoclasts. Thus, these results indicate that abLIM1 negatively controls osteoclast differentiation by regulating cell migration and fusion mediated via actin formation.