AJAP1 (adherens junctions associated protein 1) is a transmembrane protein that functions as a tumor suppressor and synaptic regulator with critical roles in cell adhesion, migration, and neuronal signaling 1. The protein localizes to adherens junctions and dendrites, where it binds to β-catenin and GABA type B receptors (GBRs) 23. AJAP1's primary mechanism involves regulating cell-cell adhesion by preventing β-catenin nuclear translocation, thereby suppressing epithelial-to-mesenchymal transition and ZEB1 transcription 3. In neurons, AJAP1 trans-synaptically recruits GBRs to presynaptic sites, enabling postsynaptic regulation of presynaptic inhibition 2. Disease relevance is significant across multiple conditions. In cancers including gliomas, breast, hepatocellular, and prostate cancers, AJAP1 is frequently downregulated through promoter hypermethylation, correlating with increased invasion, metastasis, and poor survival 1435. In neurological disorders, AJAP1 variants are associated with epilepsy and neurodevelopmental disorders, with loss-of-function mutations reducing GBR-mediated inhibition 26. Clinically, AJAP1 expression serves as a prognostic biomarker, with decreased expression predicting worse outcomes in multiple cancer types and potential therapeutic implications for both oncology and neurology 78.