TBRG4 regulates ubiquitination of Beclin1 and participates in autophagy pathway to inhibit intervertebral disc degeneration.

Background: IDD is commonly observed in symptomatic spinal disorders and is associated with mitochondrial dysfunction and NPC apoptosis. Current therapeutic targets remain theoretical, highlighting the need to explore alternative molecular targets.

Purpose: To investigate the role of TBRG4 in regulating mitochondrial function, autophagy, and apoptosis in IDD, and to evaluate its therapeutic potential.

Study design/settings: This study combines molecular and cellular biology techniques with an in vivo rat model of IDD.

Methods: Human NPCs were isolated and characterized from IDD patients and controls. TBRG4 expression was modulated using plasmid transfection. Autophagy, apoptosis, and mitochondrial function were assessed using immunofluorescence, Western blot, and flow cytometry. Co-immunoprecipitation and mass spectrometry identified TBRG4-interacting proteins. A rat IDD model evaluated TBRG4's therapeutic effects in vivo.

Results: TBRG4 expression was significantly downregulated in degenerated NPCs. TBRG4 knockdown exacerbated mitochondrial dysfunction, increased apoptosis via the BCL2/C-caspase3 pathway, and inhibited autophagy. Mechanistically, TBRG4 interacted with Beclin1 and reduced its ubiquitination, thereby promoting autophagy. Overexpression of TBRG4 in NPCs restored mitochondrial function and suppressed apoptosis. In a rat IDD model, TBRG4 overexpression alleviated disc degeneration, as evidenced by MRI, histological analysis, and decreased Pfirmmann grading.

Conclusions: TBRG4 plays a crucial protective role in IDD by promoting autophagy and maintaining mitochondrial homeostasis. It interacts with Beclin1 to enhance autophagy by reducing ubiquitination. TBRG4 shows potential as a novel therapeutic target for IDD.

Clinical significance: TBRG4-based therapies may represent a promising strategy to mitigate IDD progression, improve NPC survival, and restore disc function. Future research should focus on the development of TBRG4 activators and large-scale clinical validation.