Abstract
Adult-bone homeostasis is maintained through the reciprocal actions of osteoclasts and osteoblasts, which respectively resorb and deposit new bone. Excessive osteoclast activity leads to bone loss and contributes to conditions like osteoporosis. Osteoclasts form a specialized adhesion structure called the actin ring that is crucial for bone resorption and relies on both the actin and microtubule cytoskeletons. Our previous studies identified the β-tubulin isotype TUBB6 as a regulator of actin ring dynamics essential for osteoclast function, and found ARHGAP10, a negative regulator of the GTPases CDC42 and RHOA, as a potential mediator of TUBB6 function. Here we show that ARHGAP10 is a novel microtubule-associated protein critical for osteoclast function. ARHGAP10 directly binds microtubules through its BAR-PH domain, which requires positively-charged lysine residues K37, K41 and K44 within the BAR domain. CRISPR/Cas9 mediated knockout of Arhgap10 affects the morphology of the actin ring and impairs osteoclast resorption activity, correlated with altered actin ring dynamics. Complementation experiments reveal that the ability of ARHGAP10 to bind microtubules and to negatively regulate RHO-GTPases are essential for its role in osteoclast resorption activity. These findings uncover a novel cytoskeletal regulator in osteoclasts and suggest that targeting the microtubule-actin interface via ARHGAP10 could represent a therapeutic strategy in bone loss disorder.