Loss of Myo5b results in apical bulk endocytosis a pathway that shares characteristics with neuronal activity–dependent bulk endocytosis. (A) VAMP4 (red), an essential cargo protein during ADBE, is present in the brush border of neonatal control enterocytes. In Myo5b KO mice, VAMP4 is still present on the apical membrane; however, numerous intracellular inclusions are positive for VAMP4. Many VAMP4-positive inclusions were double-positive for DPPIV (white) in Myo5b KO enterocytes. (B) The F-bar protein Pacsin 2 (red) was also observed on the apical membrane of control enterocytes. In Myo5b KO enterocytes, Pacsin 2 was expressed on the apical membrane and surrounding inclusions. n = 6 mice per group. Scale bars = 50 µm.