BCAP31 is an abundant endoplasmic reticulum (ER) transmembrane protein that functions as a chaperone involved in protein quality control and transport 12. The protein plays critical roles in exporting secreted proteins from the ER, recognizing misfolded proteins, and targeting them for ER-associated degradation (ERAD) 12. Additionally, BCAP31 facilitates mitochondrial respiratory chain assembly by promoting translocation of NDUFS4 and NDUFB11 to mitochondria through interaction with TOMM40 3. Under ER stress conditions, BCAP31 delocalizes from ER-mitochondria contact sites and binds BCL2, potentially contributing to apoptotic signaling 34. Clinically, loss-of-function mutations in BCAP31 cause X-linked developmental disorders characterized by severe developmental delay, deafness, dystonia, and cerebral hypomyelination 5. Recent studies demonstrate that BCAP31 dysfunction leads to mitochondrial impairment, including increased ROS production, reduced ATP levels, and decreased mitochondrial membrane potential 6. The protein has emerged as a potential biomarker in various cancers, where overexpression correlates with poor prognosis and enhanced tumor cell proliferation, migration, and invasion through multiple signaling pathways 789.