A “DUBTAC” targeting GLUL deubiquitination promotes BMSC osteogenic differentiation and implant osseointegration in type 2 diabetes

INTRODUCTION: Osseointegration in patients with type 2 diabetes mellitus (T2DM) is poor, and overcoming osseointegration impairment safely and efficiently remains challenging. OBJECTIVES: To investigate the effect and process of GLUL on the osteogenic differentiation and osseointegration in T2DM by using BMSCs. METHODS: Human BMSCs were used for osteogenic differentiation in vitro and vivo, while C57BL/6 mice and GK male rats were used for in vivo osseointegration study. Cell transfection, western blotting, coimmunoprecipitation test, microscopic thermography, transcriptome sequencing and bioinformatic analysis favored in discovery of potential target protein and specific sites. RESULTS: The expression of glutamine synthetase (GLUL) is downregulated in the jawbone-derived BMSCs of T2DM patients. In this study, we found that GLUL protein homeostasis is important for the osteogenic differentiation of BMSCs and implant osseointegration. Synovial cell apoptosis inhibitor 1 (SYVN1) mediates the ubiquitination of GLUL protein at K259/334A, reducing GLUL protein expression and affecting the osteogenic differentiation of BMSCs. On this basis, we developed a GLUL-DUBTAC called HY-X3369, which is linked by the GLUL ligand HY-126351 and the covalent ligand of the deubiquitinase OTUB1 to target the GLUL ubiquitination site and reduce GLUL ubiquitination. Through pathway degradation, HY-X3369 maintains the protein homeostasis of GLUL in T2DM. HY-X3369 promotes the osteogenic differentiation of jawbone BMSCs from T2DM patients and inhibits GLUL degradation. In vivo evaluation further confirmed that HY-X3369 promotes osseointegration in GK rats. CONCLUSIONS: This study reveals a promising strategy involving HY-X3369 to promote the function of BMSCs and osseointegration in T2DM, providing a theoretical basis and candidate methods for improving osseointegration in T2DM patients.