Artículos de revistas
Apical distribution of HFE–b2-microglobulin is associated with inhibition of apical iron uptake in intestinal epithelia cells
Fecha
2005-10-03Registro en:
BIOMETALS, Volume: 19, Issue: 4, Pages: 379-388, 2006
0966-0844
Autor
Arredondo Olguín, Miguel Armando
Tapia, Victoria
Rojas, Alejandro
Aguirre, Pabla
Reyes, Francisca
Marzolo Canales, María Paz
Núñez González, Marco
Institución
Resumen
Mutations in the HFE gene result in hereditary hemochromatosis, a disorder of iron metabolism characterized
by increased intestinal iron absorption. Based on the observation that ectopic expression of HFE
strongly inhibits apical iron uptake (Arredondo et al., 2001, FASEB J 15, 1276–1278), a negative regulation
of HFE on the apical membrane transporter DMT1 was proposed as a mechanism by which HFE regulates
iron absorption. To test this hypothesis, we investigated: (i) the effect of HFE antisense oligonucleotides on
apical iron uptake by polarized Caco-2 cells; (ii) the apical/basolateral membrane distribution of HFE, b-2
microglobulin and DMT1; (iii) the putative molecular association between HFE and DMT1. We found
that HFE antisense treatment reduced HFE expression and increased apical iron uptake, whereas transfection
with wild-type HFE inhibited iron uptake. Thus, an inverse relationship was established between
HFE levels and apical iron uptake activity. Selective apical or basolateral biotinylation indicated preferential
localization of DMT1 to the apical membrane and of HFE and b-2 microglobulin (b2m) to the
basolateral membrane. Ectopic expression of HFE resulted in increased distribution of HFE–b2m to the
apical membrane. The amount of HFE–b2m in the apical membrane inversely correlated with apical iron
uptake rates. Immunoprecipitations of HFE or b2m with specific antibodies resulted in the co-precipitation
of DMT1. These results sustain a model by which direct interaction between DMT1 and HFE–b2m in the
apical membrane of Caco-2 cells result in down-regulation of apical iron uptake activity.