Plasma membrane delivery, endocytosis and turnover of transcobalamin receptor in polarized human intestinal epithelial cells

摘要: Cells that are metabolically active and in a high degree of differentiation proliferation require cobalamin (Cbl: vitamin B(12)) they obtain it from the circulation bound to transcobalamin (TC) via receptor (TC-R). This study has investigated plasma membrane dynamics TC-R expression polarized human intestinal epithelial Caco-2 cells using techniques pulse-chase labelling, domain-specific biotinylation cell fractionation. Endogenously synthesized turned over with half-life (T(1/2)) 8 h following its delivery basolateral (BLM). The T(1/2) BLM was 15 min delivered endocytosed subsequently degraded by leupeptin-sensitive proteases. However, about 15% transcytosed (T(1/2), 45 min) apical membranes (BBM) where underwent endocytosis degraded. both BBM inhibited Brefeldin A tunicamycin, but not wortmannin or leupeptin. Colchicine BBM, BLM. At steady state, associated megalin these proteins were enriched an intracellular compartment which also contained Rab5 transferrin receptor. These results indicate rapid domains cells, undergoes constitutive degradation expressed complexes during transcytosis