Klotho upregulates the interaction between RANK and TRAF6 to facilitate RANKL-induced osteoclastogenesis via the NF-κB signaling pathway

Abstract

Background: α-Klotho (Klotho) plays a wide range of roles in pathophysiological processes, such as lowturnover osteoporosis observed in klotho mutant mice (kl/kl mice). However, the precise function and underlying mechanism of klotho during osteoclastogenesis are not fully understood. Here, we investigated the effects of klotho on osteoclastogenesis induced by receptor activator of nuclear factor kappa-B ligand (RANKL). Methods:The effects of klotho deficiency on osteoclastogenesis were explored using kl/kl mice both in vivo and in vitro. In in vitro experiments, lentivirus transfection, real-time quantitative PCR (RT-qPCR) analysis, western blot analysis, immunostaining, RNA-seq analysis, differential pathway analysis, Energy-based protein docking analysis and co-immunoprecipitation were used for deeply investigating the effects of klotho on RANKL-induced Osteoclastogenesis and the underlying mechanism.Results: We found that klotho deficiency impaired osteoclastogenesis. Furthermore, in vitro studies revealed that klotho facilitated osteoclastogenesis and upregulated the expression of c-Fos and nuclear factor of activated T cells cytoplasmic 1 (NFATc1) during osteoclastogenesis. Mechanistically, we confirmed that klotho co-localized with nuclear factor kappa B (RANK) and facilitated the interaction between activated RANK and TNFR-associated factor 6 (TRAF6), thus klotho exerts its function in osteoclastogenesis through the activation of the NF-κB signaling pathway.Conclusions: Klotho promotes RANKL-induced osteoclastogenesis through upregulating the interaction between RANK and TARF6, Targeting on klotho may be an attractive therapeutic method for osteopenic diseases.

Klotho in Osx+-mesenchymal progenitors exerts pro-osteogenic and anti-inflammatory effects during mandibular alveolar bone formation and repair

“…This indicates that the decreased bone resorption observed in mutants is the direct result of the functional deletion of Klotho in Osx + -mesenchymal progenitors. Although osteoclast-specific Klotho also promoted Rankl-induced osteoclastogenesis, 26 OsxCre;KL fl/fl mice had conditional ablation of Klotho in Osx + -progenitors but not in osteoclasts, suggesting that Klotho is involved in osteoblast-dependent bone resorption, at least in part, by the regulation of Rankl in osteoblasts. It has been suggested that in bone marrow mesenchymal stem cells, RANKL binding to RANK activates RANKL signaling, which negatively regulates osteoblast differentiation.…”

“…This phenotype is similar to that of Klotho-hypomorphic mice, which exhibited reduced osteoblast and osteoclast numbers and lower cortical bone thickness. 22 , 26 Moreover, deletion of Klotho in long bone mesenchymal stem cells ( Prx1Cre;KL fl/fl ), as well as in osteocytes ( Dmp1Cre;KL fl/fl ), both showed a trend towards reduced osteoclastic resorption parameters. 11 , 27 …”