Caco-2 Intestinal Epithelial Cells Absorb Soybean Ferritin by u2 AP2-Dependent Endocytosis1,2Reportar como inadecuado

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Iron deficiency, a condition currently affecting ;3 billion people, persists in the 21st century despite half a millennium ofmedical treatment. Soybean ferritin SBFn, a large, stable protein nanocage around a mineral with hundreds of iron andoxygen atoms, is a source of nutritional iron with an unknown mechanism for intestinal absorption. Iron absorption fromSBFn is insensitive to phytate, suggesting an absorption mechanism different from for the ferrous transport. Here, weinvestigated the mechanism of iron absorption from mineralized SBFn using Caco-2 cells polarized in bicameral inserts asan intestinal cell mode and analyzed binding, internalization and degradation with labeled SBFn 131I or fluorescent labels,confocal microscopy, and immunoanalyses to show: 1 saturable binding to the apical cell surface; dissociation constant of7.7560.88 nmol-L; 2 internalization of SBFn that was dependent on temperature, concentration, and time; 3 entrance ofSBFn iron into the labile iron pool calcein quenching; 4 degradation of the SBFn protein cage; and 5 assembly peptide 2AP2-clathrin-dependent endocytosis sensitivity of SBFn uptake to hyperosmolarity, acidity, and RNA interference to them2 subunit of AP2, and resistance to filipin, a caveolar endocytosis inhibitor. The results support a model of SBFnendocytosis through the apical cell membrane, followed by protein cage degradation, mineral reduction-dissolution, and ironentry to the cytosolic iron pool. The large number of iron atoms in SBFn makes iron transport across the cell membrane amuch more efficient event for SBFn than for single iron atoms as heme or ferrous ions.

Autor: San Martín, Carol; - Garri, Carolina; - Núñez González, Marco; - Pizarro Aguirre, Fernando; - Walter, Tomas; - Theil, Elizabe



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