Rab7-Dependent Endocytic Pathways Play an Important Role in Nutrient Absorption during Pre-Weaning Growth

Abstract

Enterocytes in neonatal rodent endocytose milk materials as macromolecule and digest them into small nutrient molecules. Bulk endocytic membrane flow sustaining nutrient uptake inevitably brings the plasma membrane into large lysosomes, as known as supranuclear vesicles or apical vacuoles which exhibit a unique morphology in infant enterocytes. Endocytic delivery to the large vacuoles required the function of Rab7 GTPase. The Rab7-deficient neonatal enterocytes became filled with abnormal gigantic vacuoles as they migrated from the intervillus pocket to the distal region of the villi and they became defective in taking up macromolecules. Infant animals lacking Rab7 in enterocytes exhibited growth retardation. These results showed that the Rab7-dependent endocytic pathways play an important role in nutrient absorption during pre-weaning growth.