TMUB2 (transmembrane and ubiquitin-like domain containing 2) is an ER membrane protein involved in quality control and protein degradation. As a component of the ERAD (ER-associated degradation) pathway, TMUB2 functions within a specialized ubiquitin ligase complex consisting of RNF185, TMUB1/2, and TMEM259/Membralin that selectively degrades misfolded ER membrane proteins 1. This complex cooperates with cytosolic ubiquitin ligase UBE3C and p97 ATPase to remove defective membrane substrates, demonstrating remarkable substrate specificity in ERAD branch function 1. Clinically, TMUB2 has emerged as a novel candidate gene associated with osteoporosis susceptibility. Transcriptome-wide association studies identified TMUB2 among 14 novel genes with potential causal effects on bone mineral density and fracture risk through expression or RNA splicing mechanisms 2. Additionally, TMUB2 shows differential expression in early-stage prostate cancer progression, suggesting roles in ubiquitin-proteasome pathway dysregulation associated with cancer progression 3. These findings indicate TMUB2's importance in both physiological protein quality control and disease-related proteasomal dysfunction, positioning it as a potential biomarker and therapeutic target across multiple pathologies.