Antibodies against ClC7 inhibit extracellular acidification-induced Cl⁻ currents and bone resorption activity in mouse osteoclasts.

The Cl⁻ channel/transporter ClC7 is crucial for osteoclastic bone resorption and might become a therapeutic target for osteoporosis. In this study, we raised anti-ClC7 polyclonal antibodies against three different peptide sequences, including G215, P249, and R286, which are the mutation regions found in autosomal dominant osteopetrosis type II patients and examined the effects of these antibodies on the ClC7 Cl⁻ current induced by extracellular acidification (acid-activated Cl⁻ current) using the whole-cell patch clamp technique and bone resorption activity in mouse osteoclasts. Intracellular dialysis of osteoclasts with antibodies to intracellular G215 (Ab-G215) and extracellular application of antibodies to extracellular P249 (Ab-P249) or R286 (Ab-R286) inhibited the acid-activated Cl⁻ current. These antibodies also suppressed the acid-activated Cl⁻ current in ClC7 overexpressing Raw264.7 cells; however, Cl⁻ currents evoked by hypotonic stimulation and the inherent inwardly rectifying K+ currents in mouse osteoclasts were unaffected by these antibodies. Furthermore, extracellularly applied Ab-P249 and Ab-R286 also reduced bone resorption activity. Our results demonstrate that these antibodies specifically block ClC7 in mouse osteoclasts. Thus, anti-ClC7 antibodies have potential promise for treatment of osteoporosis.