TY - JOUR
T1 - Subcellular location of heme oxygenase 1 and 2 and divalent metal transporter 1 in relation to endocytotic markers during heme iron absorption
AU - West, Adrian
AU - Oates, Phillip
PY - 2008
Y1 - 2008
N2 - Background andHeme is an important dietary micronutrient, although its absorptive mechanisms are poorly understood. One hypothesis suggests enterocytes take up heme by receptor-mediated endocytosis (RME) which then undergoes catabolism by heme oxygenase (HO) inside internalized vesicles. This would require the translocation of HO-1 or HO-2 to endosomes and/or lysosomes and the presence of a transporter, possibly divalent metal transporter 1 (DMT1), to transfer released iron to the cytoplasm. Currently, the location of HO-1 and HO-2 in enterocytes is unknown.Methods: We studied the subcellular location of HO-1, HO-2, and DMT1 in the proximal small intestine of rats by confocal immunofluorescence microscopy up to 4 h after a dose of heme or ferrous iron. Double-labeling was performed with endocytotic (EEA1, Lamp1) and structural markers (F-actin).Results: HO-1 was distributed evenly throughout the cytoplasm of enterocytes and did not colocalize with endocytotic markers in any condition. HO-2 staining remained constant with dosing, presenting as a dense band in the apical cytoplasm that colocalized extensively with endosomes. DMT1 staining was markedly reduced by ferrous iron, but not heme and did not exhibit colocalization with endocytotic markers.Conclusion: The subcellular location of HO-2 is consistent with the RME hypothesis for heme uptake and may suggest a possible role for this enzyme in heme degradation. The lack of translocation of DMT1 with heme dosing suggests another protein may be present to transport iron released from heme.
AB - Background andHeme is an important dietary micronutrient, although its absorptive mechanisms are poorly understood. One hypothesis suggests enterocytes take up heme by receptor-mediated endocytosis (RME) which then undergoes catabolism by heme oxygenase (HO) inside internalized vesicles. This would require the translocation of HO-1 or HO-2 to endosomes and/or lysosomes and the presence of a transporter, possibly divalent metal transporter 1 (DMT1), to transfer released iron to the cytoplasm. Currently, the location of HO-1 and HO-2 in enterocytes is unknown.Methods: We studied the subcellular location of HO-1, HO-2, and DMT1 in the proximal small intestine of rats by confocal immunofluorescence microscopy up to 4 h after a dose of heme or ferrous iron. Double-labeling was performed with endocytotic (EEA1, Lamp1) and structural markers (F-actin).Results: HO-1 was distributed evenly throughout the cytoplasm of enterocytes and did not colocalize with endocytotic markers in any condition. HO-2 staining remained constant with dosing, presenting as a dense band in the apical cytoplasm that colocalized extensively with endosomes. DMT1 staining was markedly reduced by ferrous iron, but not heme and did not exhibit colocalization with endocytotic markers.Conclusion: The subcellular location of HO-2 is consistent with the RME hypothesis for heme uptake and may suggest a possible role for this enzyme in heme degradation. The lack of translocation of DMT1 with heme dosing suggests another protein may be present to transport iron released from heme.
U2 - 10.1111/j.1440-1746.2007.05047.x
DO - 10.1111/j.1440-1746.2007.05047.x
M3 - Article
C2 - 17614955
SN - 0815-9319
VL - 23
SP - 150
EP - 158
JO - Journal of Gastroenterology and Hepatology
JF - Journal of Gastroenterology and Hepatology
IS - 1
ER -