MAGI1 is a cytoplasmic scaffolding protein that plays critical roles in cell junction stability, tumor suppression, and vascular function. As a scaffolding protein, MAGI1 stabilizes cadherin-mediated cell-cell adhesion in epithelial and endothelial cells through its PDZ domains 1. The protein localizes to mature focal adhesions where it colocalizes with paxillin, β3-integrin, and other adhesion components, regulating focal adhesion dynamics, cell spreading, and actin stress fiber formation 2. MAGI1 functions as a tumor suppressor, with decreased expression observed in multiple cancers including hepatocellular, colorectal, cervical, breast, brain, and gastric cancers 1. It modulates oncogenic pathways including PI3K/AKT and Wnt/β-catenin signaling 3. In endothelial cells, MAGI1 undergoes post-translational modifications under disturbed flow conditions, linking endothelial activation to ER stress and contributing to atherosclerosis 4. The protein forms a growth-suppressive complex with PP2A in certain cancer contexts 5 and plays roles in DNA damage response in estrogen receptor-positive breast cancer 6. MAGI1 expression is regulated by various mechanisms including inflammation, mechanical stress, and microRNAs such as miR-205-5p 7.