UGGT1 (UDP-glucose glycoprotein glucosyltransferase 1) functions as a critical 'folding sensor' and gatekeeper of protein quality control in the endoplasmic reticulum (ER) 1. The enzyme recognizes glycoproteins with minor folding defects and reglucosylates their N-linked glycans, allowing these proteins to re-enter the lectin-chaperone folding cycle 2. This reglucosylation activity is essential for determining the fate of glycoproteins through competition between folding and degradation pathways 2. UGGT1 functions as a heterodimer with selenoprotein F (SEP15/SelenoF), which enhances its oxidoreductase capacity 13. Beyond general protein folding, UGGT1 cooperates with TAPBPR to quality-control MHC I complexes during antigen presentation 4. Clinically, bi-allelic UGGT1 loss-of-function variants cause congenital disorder of glycosylation (CDG), characterized by developmental delay, intellectual disability, seizures, microcephaly, and variable organ involvement 5. Pan-cancer analysis reveals UGGT1 overexpression correlates with advanced cancer stage, poor survival, and altered immune infiltration across multiple tumor types, establishing it as a therapeutic target 6. Additionally, UGGT1 upregulation in Alzheimer's disease brain capillaries associates with enhanced protein processing and N-glycosylation capacity 7.