IL1β and TNFα promote RANKL-dependent adseverin expression and osteoclastogenesis

Abstract

Adseverin is an actin binding protein involved in osteoclastogenesis, but its role in inflammation-induced bone loss is not defined. We examined whether IL1β and TNFα regulate adseverin expression to control osteoclastogenesis in mouse primary monocytes and RAW264.7 cells. Adseverin co-localized with subcortical actin filaments and was enriched in fusopods of fusing cells. In precursor cells, adseverin overexpression boosted RANKL-induced multinucleated cell formation. IL1β and TNFα enhanced RANKL-dependent TRAcP activity by 1.6-fold and increased formation of multi-nucleated cells (for cells with >3 nuclei: 2.6-fold by IL1β; 3.3-fold by TNFα). IL1β and TNFα did not enhance osteoclast formation in Ads knockdown cells. RANKL-dependent adseverin expression in bone marrow cells was increased by both IL1β (5.4-fold) and TNFα (3.3-fold). Luciferase assays demonstrated that RANKL-enhanced adseverin expression involved transcriptional regulation of the adseverin promoter. Activation of the adseverin promoter was restricted to a 1,118 bp sequence upstream of the transcription start site; this sequence contained several NF-κB binding sites. IL1β and TNFα promoted RANKL-induced pre-OC migration. We conclude that IL1β and TNFα enhance RANKL-dependent adseverin expression, which contributes to fusion processes in osteoclastogenesis.