UBQLN1 (ubiquilin 1) is a critical protein quality control factor that functions as a chaperone and shuttle factor for proteasomal degradation. The protein contains ubiquitin-like (UBL) and ubiquitin-associated (UBA) domains that facilitate its role in protein homeostasis 1. UBQLN1 plays essential roles in multiple cellular processes including the unfolded protein response during ER stress and regulation of presenilin 1 levels through aggresome targeting [UniProt]. In mitochondrial quality control, UBQLN1 associates with unimported mitochondrial membrane protein precursors and facilitates their proteasomal degradation through interaction with E3 ubiquitin ligase RNF126 2. The protein is crucial for telomere maintenance in human embryonic stem cells by promoting mitochondrial function and preventing oxidative stress-induced damage 3. UBQLN1 also regulates cancer progression, with upregulation contributing to sorafenib resistance in hepatocellular carcinoma through PGC1β degradation and mitochondrial biogenesis modulation 4. Loss of UBQLN1 promotes epithelial-mesenchymal transition and enhances tumor progression in lung adenocarcinoma 1. Additionally, UBQLN1 mediates protein aggregate degradation and participates in glycolytic regulation through Pgm1 ubiquitination 5. Despite some studies suggesting associations with Alzheimer's disease, meta-analysis shows no significant correlation with disease risk 6.