ATP8B3 is a P4-ATPase flippase that catalyzes ATP hydrolysis coupled to phospholipid translocation from the outer to inner membrane leaflet, maintaining asymmetric phospholipid distribution 1. Unlike other class 1 P4-ATPases, ATP8B3 does not interact with CDC50 proteins and remains localized in the endoplasmic reticulum rather than trafficking to the plasma membrane 1. ATP8B3 has been implicated in sperm cell function, potentially maintaining phosphatidylserine asymmetry in spermatozoa membranes and involvement in acrosome reactions 2. Recent studies have identified ATP8B3 as having broader physiological roles beyond reproductive function. Genetic variants in ATP8B3 are associated with aspirin-exacerbated respiratory disease in asthmatics, where minor alleles may confer protection through increased ATP8B3 production 3. In colon adenocarcinoma, ATP8B3 contributes to establishing an immunosuppressive microenvironment and correlates with PD-L1 expression, suggesting its inhibition could enhance immunotherapy efficacy in microsatellite instability-high tumors 4. Additionally, ATP8B3 variants have been associated with adipocytokine regulation and triglyceride levels in genetic studies 56, and cardiac abnormalities in mouse models 7, indicating diverse roles in metabolic and cardiovascular physiology beyond its established membrane lipid transport function.