SLC7A3 encodes CAT-3 (cationic amino acid transporter 3), a plasma membrane transporter that mediates sodium-independent uptake of cationic L-amino acids including L-arginine, L-lysine, and L-ornithine through passive diffusion 1. The protein functions as a uniporter with moderately trans-stimulated transport activity and shows selective brain expression 23. SLC7A3 plays critical roles in cellular arginine metabolism, with its upregulation enabling cells to overcome arginine and lysine limitations by increasing uptake rates 4. The transporter exhibits context-dependent effects in cancer: while SLC7A3-mediated arginine uptake promotes osteosarcoma metastasis through SP1 stabilization pathways 5, increased SLC7A3 expression inhibits breast cancer cell proliferation and predicts favorable prognosis 6. Disease relevance includes associations with neurodevelopmental disorders, as hypomorphic SLC7A3 variants have been identified in males with autism spectrum disorders, causing severe transport defects due to altered protein stability or trafficking 2. Additionally, SLC7A3 variants represent potential causes of childhood epilepsy and developmental delay 7. The gene also functions in embryonic stem cell self-renewal, with SLC7A3 downregulation occurring during differentiation 8. These findings establish SLC7A3 as a critical regulator of cationic amino acid homeostasis with significant implications for neurological function and cancer biology.