SPNS2 encodes a lipid transporter that specifically mediates export of sphingosine-1-phosphate (S1P) from cells, playing crucial roles in immune function and hearing 1. The protein functions through facilitated diffusion, distinct from other MFS lipid transporters, and undergoes conformational changes between inward-facing and outward-facing states to transport S1P across cell membranes 1. SPNS2 is essential for establishing S1P concentration gradients between high circulating levels and low tissue concentrations, which control lymphocyte trafficking and egress from lymphoid organs 2. The transporter is required for T-cell egress from lymph nodes during immune responses and immature B-cell egress from bone marrow 2. Beyond immune function, SPNS2 is critical for auditory function, as S1P release in the inner ear maintains the endocochlear potential necessary for hearing 3. Pathogenic mutations in SPNS2 cause autosomal recessive deafness (DFNB115) by ablating the protein's S1P export activity 3. The transporter also exports FTY720-P (fingolimod), making it central to the pharmacokinetics of this multiple sclerosis therapeutic 3. SPNS2 represents a potential therapeutic target for autoimmune diseases, cancer, and inflammatory conditions, with several inhibitors under development 45.