We earlier showed that leucine-rich glioma inactivated 3 (LGI3) colocalizes with amyloid beta peptide (Abeta) taken up by astrocytes both in vitro and in vivo, and that LGI3 accumulated with endocytosis-associated proteins in aged monkey brains. In this study, we confirmed that LGI3 localizes to the endocytic pathway and found that its accumulation is caused by endocytic perturbation. Most notably, RNA interference experiments demonstrated that the downregulation of LGI3 clearly inhibited Abeta uptake by cultured rat astrocytes, moreover, transferrin uptake by both astrocytes and neuronal cells. Together with our earlier findings, our results suggest that LGI3 is involved in Abeta uptake by astrocytes and even endocytosis itself.