E3 ubiquitin-protein ligase synoviolin (SYVN1)

E3 ubiquitin-protein ligase synoviolin (SYVN1, also known as HRD1) is an endoplasmic reticulum-resident E3 ubiquitin ligase central to the ER-associated degradation (ERAD) pathway, responsible for tagging misfolded or unfolded proteins for proteasomal degradation to maintain cellular proteostasis[2][3][5]. SYVN1’s antiapoptotic function in synovial cells contributes to synovial overgrowth and pathology in rheumatoid arthritis by degrading pro-apoptotic ER stress proteins such as IRE1 and repressing apoptosis[4][6]. SYNV1 further regulates energy metabolism by ubiquitinating and destabilizing peroxisome proliferator-activated receptor coactivator PGC-1β, thus negatively controlling mitochondrial number, thermogenesis, and energy expenditure[1]. Elevated expression or activity of synoviolin is implicated in rheumatologic disease, metabolic disorders, and cell survival in neuronal models—making it a potential therapeutic target in diseases with dysregulated apoptosis, metabolism, or ER stress[1][4][5][6].

Other names

HMG-CoA reductase degradation 1 homolog (HRD1)Synovial apoptosis inhibitor 1KIAA1810DER3RING-type E3 ubiquitin transferase synoviolinsynoviolin

Targeted inhibition of E3 ubiquitin ligase activity (e.g., by LS-102 prevents degradation of thermogenic coactivator PGC-1β, promoting mitochondrial activity and energy expenditure)[1] Potential restoration of pro-apoptotic signaling in synovial cells via prevention of IRE1 degradation[4]