RAB11FIP4 is a regulator of endocytic trafficking that functions as an adaptor protein controlling membrane recycling pathways. Structurally, it acts as a small GTPase-binding protein that localizes to recycling endosomes and participates in delivery of endosomal membranes to cellular compartments 1. Its primary established mechanism involves regulating endocytic recycling and membrane trafficking during cytokinesis, where it delivers recycling endosome membranes to the cleavage furrow during late cell division stages. RAB11FIP4 plays an emerging role in lysosomal homeostasis and autophagy regulation. In cystinosis models, RAB11FIP4 downregulation impairs autophagic flux and lysosomal function; reconstituting RAB11FIP4 expression restored normal autophagosome levels, decreased LC3B-II accumulation, and increased LAMP2A localization at lysosomes, ultimately reducing endoplasmic reticulum stress 1. Additionally, RAB11FIP4 regulates lysosomal trafficking and autophagy during mycobacterial infection 2. Clinically, RAB11FIP4 has been implicated in multiple disease contexts. It was identified as a candidate gene harboring de novo variants in neurodevelopmental disorder cohorts 3, and as a differentially expressed gene enriched in osteoarthritis-associated genomic regions and chondrocyte dedifferentiation 4. RAB11FIP4 is also downregulated in polypoidal choroidal vasculopathy and may serve as a biomarker for anti-VEGF treatment responsiveness 5. Notably, RAB11FIP4 has been identified among tumor-specific isoforms in high-grade serous ovarian cancer 6.