GOPC is a Golgi-associated protein that regulates intracellular trafficking and protein degradation. It contains PDZ and coiled-coil motifs and localizes to the trans-Golgi network, where it modulates the subcellular localization and turnover of multiple cargo proteins. GOPC interacts with the GTPase ARFRP1 to control plasma membrane trafficking of the SNARE protein SNAP25, a mechanism essential for glucose-stimulated insulin secretion from pancreatic β-cells 1. The protein also facilitates basolateral sorting of syndecan-1 in polarized epithelial cells, likely through effects on Golgi organization 2. During herpes simplex virus 1 infection, the viral protein pUL56 targets GOPC for proteasomal degradation, resulting in loss of cell-surface Toll-like receptor 2 3. Clinically, GOPC gains oncogenic function through fusion with the receptor tyrosine kinase ROS1 in lymphatic malformations and glioblastomas. GOPC-ROS1 fusion promotes proliferation and migration of lymphatic endothelial cells by impairing tight junctions 4. In glioblastoma patients, GOPC-ROS1 fusions detected in circulating cell-free DNA may be amenable to tyrosine kinase inhibitors such as crizotinib, entrectinib, or larotrectinib 5. GOPC expression is also altered in preeclampsia and associated with diabetes, suggesting broader involvement in metabolic and vascular diseases.