The UBA5-GABARAP-PERK axis promotes cartilage degeneration in osteoarthritis by inhibiting autophagy and promoting endoplasmic reticulum stress

Abstract

Abstract purpose Osteoarthritis (OA) is one of the most common causes of disability in the elderly. Ubiquitin-like modifier-activated enzyme 5 (UBA5) is a critical factor in preventing cellular autophagy and causing endoplasmic reticulum stress but has not been studied in OA. We aimed and explored the involvement of the UBA5-GABARAP-PERK axis in regulating cartilage matrix metabolism and apoptosis in osteoarthritis. Methods Oxidative stress was induced using IL-1β, which disrupted the homeostatic balance of cartilage. In in vivo and in vitro experiments, Western blot, qt-QPCR, scanning electron microscopy, immunofluorescence, and mCherry-GFP-LC3 plasmid were applied to observe OA-associated cartilage degeneration, ROS production, mitochondrial function, autophagic flux, endoplasmic reticulum stress and matrix after application of UBA5 selective inhibitor DKM2-93, knockdown or overexpression of UBA5 changes in metabolic indicators. UBA5 adeno-associated virus was injected into the cavity of mice, and a mouse OA model was induced by DMM surgery. Histological analysis of cartilage degeneration was performed using immunohistochemistry, Safranin-O staining, HE staining, Micro-CT, OARSI, and synovitis score. Results Expression of UBA5 was increased in chondrocytes receiving IL-1β intervention. Knockdown of UBA5 in vivo and in vitro inhibited OA-related chondrogenic degeneration, alleviated mitochondrial dysfunction, stimulated autophagy, inhibited endoplasmic reticulum stress, reduced catabolism, and increased anabolism. Overexpression of UBA5 also promotes oxidative stress and disrupts the molecular signature of healthy chondrocytes. Mechanistically, the destructive function of UBA5 may be attributed to the activation of the PERK/ATF4 signaling pathway. Through immunoprecipitation experiments, UBA5 was shown to inhibit autophagy by interacting with GABARAP to activate the PERK signaling pathway. Inhibition of PERK attenuated UBA5-induced osteoarthritis. Our findings suggest that Jun-B and C-Jun transcription factors may promote UBA5 expression and inhibition of UBA5 expression by in vivo application of adeno-associated virus, reduce chondrocyte death, attenuate cartilage degeneration, and promote subchondral bone remodeling. Conclusions This study revealed that UBA5 might regulate chondrocyte matrix catabolism and anabolism through the UBA5-GABARAP-PERK axis, suggesting a potential role for UBA5 in OA cartilage injury.