SLC3A1 encodes a chaperone protein that facilitates the assembly and trafficking of functional amino acid transporter heteromers to the plasma membrane 12. It primarily associates with SLC7A9 to form a system b(0,+)-like transporter complex mediating electrogenic exchange between cationic amino acids (lysine, arginine, ornithine) and neutral amino acids, with particular affinity for L-cystine 12. This heterodimeric transporter serves as the major mechanism for reabsorbing L-cystine and dibasic amino acids across the brush border membrane in early proximal renal tubules 12. SLC3A1 also associates with SLC7A13 in late proximal tubules to facilitate L-cystine reabsorption via amino acid exchange. Mutations in SLC3A1 cause cystinuria, the most common genetic cause of nephrolithiasis in children, accounting for 1-2% of adult and 6-8% of pediatric kidney stone cases 34. Type A cystinuria results from biallelic SLC3A1 mutations 5, causing elevated urinary cystine excretion and formation of poorly soluble cystine calculi 6. Clinical manifestations are limited to recurrent nephrolithiasis, typically diagnosed during infancy or adolescence 3. Computational studies reveal that SLC3A1 mutations predominantly affect protein stability through loss of hydrogen bonds 7. Management focuses on reducing cystine excretion and increasing solubility through hydration, dietary modification, urinary alkalinization, and thiol-binding drugs 6.