This study reveals a novel mechanism where MST4 promotes osteoclast differentiation through the phosphorylation modification of TRAF6 for the first time.

It delineates the pivotal role of TRAF6 autoubiquitination in osteoclast activity.

The study uncovers the significant impact of the MST4-TRAF6 interaction on the progression of osteoporosis.

It provides a theoretical basis for targeting MST4 and TRAF6 as novel therapeutic approaches for osteoporosis.

This research opens new directions for further understanding osteoclast regulation and osteoporosis treatment.

Osteoporosis, characterized by excessive bone resorption driven by heightened osteoclast activity, remains a major health concern with molecular mechanisms that are not fully understood. This study explores the role of mammalian Sterile 20-like kinase 4 (MST4), a member of the Sterile 20 (Ste20) kinase family, in osteoclast differentiation and function. Analysis of blood samples from osteoporosis patients revealed a significant increase in MST4 expression compared to healthy controls, with a negative correlation to bone mineral density (BMD). In vitro experiments using stem cell-derived osteoclast models showed that MST4 knockdown reduced osteoclast differentiation and bone resorption activity, whereas MST4 overexpression enhanced these processes. In vivo studies with ovariectomized (OVX) mouse models further corroborated these findings. Mechanistically, MST4 was found to promote tumor necrosis factor receptor-associated factor 6 (TRAF6) autoubiquitination through phosphorylation, a critical event for osteoclast activation. Collectively, these results identify MST4 as a key regulator of osteoclast-mediated bone resorption in osteoporosis, suggesting that targeting the MST4–TRAF6 signaling axis may offer a novel therapeutic strategy to prevent bone loss.

Osteoporosis

MST4

TRAF6

Phosphorylation

Autoubiquitination

Osteoclast differentiation

© 2025 The Authors. Published by Elsevier B.V. on behalf of Xi’an Jiaotong University.