O-GlcNAcase transiently translocates to the cytoplasm and regulates osteoblast differentiation

Objectives

O-GlcNAcylation is a reversible post-translational modification mediated by O-GlcNAcase (OGA) and O-GlcNAc transferase (OGT). Although localization of OGT during differentiation has been well studied, the spatial regulation and role of OGA in the maturation of osteoblasts remains unclear. This study investigated the translocation of OGA and its functional effects during the differentiation of osteoblasts.

Methods

Localization of OGA was assessed in mouse calvarial osteoblastic cells using immunohistochemistry and in pre-osteoblastic MC3T3-E1 cells using in vitro staining. OGA-knockout (OGA-KO) MC3T3-E1 cells were generated to evaluate differentiation using the osteogenic markers, Sp7, Dlx5, and Runx2, alkaline phosphatase (ALP) activity, and mineralization stains (von Kossa and Alizarin red).

Results

OGA was primarily cytoplasmic in osteoblastic cells of the mouse calvaria. In MC3T3-E1 cells, OGA was translocated from the nucleus to the cytoplasm by differentiation Day 3 and was stabilized by Day 6. OGA-KO cells had enhanced differentiation, increased ALP activity and mineralization, and upregulated Sp7 and Dlx5 expression. Immunohistochemistry showed that Sp7 mirrored the shift in localization of OGA, moving from the nucleus to the cytoplasm by Day 6, whereas Runx2 remained in the nucleus throughout differentiation.

Conclusion

Our findings reveal that dynamic translocation of OGA is a key event in early differentiation of osteoblasts that regulates maturation of osteoblasts. These insights suggest a novel regulatory role for OGA and identify potential targets for therapeutic strategies in the regeneration of bone.