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Ferroportin 1 is expressed basolaterally in rat kidney proximal tubule cells and iron excess increases its membrane trafficking.

Wolff NA, Liu W, Fenton RA, Lee WK, Thévenod F, Smith CP - J. Cell. Mol. Med. (2011)

Bottom Line: FPN1 was found to be located in association with the basolateral PT membrane and within the cytosolic compartment.These data support a role for FPN1 in vectorial export of iron out of PT cells.Furthermore, under conditions of iron loading of cultured PT cells, FPN1 was trafficked to the plasma membrane suggesting a coordinated cellular response to export excess iron and limit cellular iron concentrations.

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Affiliation: Department of Physiology & Pathophysiology, University of Witten/Herdecke, Witten, Germany.

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Immunoperoxidase labelling of Liu-FPN1 in rat kidney. (A) Strong labelling is evident throughout the cortex and outer stripe of the outer medulla. Labelling is associated with tubule segments morphologically resembling PTs. No staining is observed in glomeruli or vasculature. (B) At high magnification, labelling is predominantly BLM associated, with some intracellular staining. (C) and (D) Labelling is strongest in the S1 and S2 segments, whilst weaker labelling is observed in the S3 segment (E). T, thick ascending limb; G, glomerulus. Immunogold electron microscopy of Liu-FPN1 in rat kidney. (F) In PT S1 segments (note the long, extensive invaginations of the basolateral plasma membrane), immunogold labelling of FPN1 is observed throughout the cells basolateral plasma membrane domains (arrows). (G) At high magnification FPN1 can be observed in direct association with the plasma membrane. (H) In PT S2 segments (note the numerous small lateral processes at the base of the cell), labelling is again observed in direct association with the basolateral plasma membrane. Gold particles are 10 nm. (I) FPN1 and kidney electrogenic Na-bicarbonate cotransporter-1 (NBCe1-A) immunoreactivity in rat kidney cortex. Homogenate, microsomal membranes and BLM from rat kidney cortex were separated under reducing conditions by SDS-PAGE on an 8% acrylamide gel. The blot was incubated with anti-rat FPN1 or anti-rat NBCe1-A (1:500). Characteristic bands at ∼60 and ∼130 kD for FPN1 and NBCe1-A were detected. Sizes (in kilodaltons) of molecular mass markers are indicated on the left.
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fig02: Immunoperoxidase labelling of Liu-FPN1 in rat kidney. (A) Strong labelling is evident throughout the cortex and outer stripe of the outer medulla. Labelling is associated with tubule segments morphologically resembling PTs. No staining is observed in glomeruli or vasculature. (B) At high magnification, labelling is predominantly BLM associated, with some intracellular staining. (C) and (D) Labelling is strongest in the S1 and S2 segments, whilst weaker labelling is observed in the S3 segment (E). T, thick ascending limb; G, glomerulus. Immunogold electron microscopy of Liu-FPN1 in rat kidney. (F) In PT S1 segments (note the long, extensive invaginations of the basolateral plasma membrane), immunogold labelling of FPN1 is observed throughout the cells basolateral plasma membrane domains (arrows). (G) At high magnification FPN1 can be observed in direct association with the plasma membrane. (H) In PT S2 segments (note the numerous small lateral processes at the base of the cell), labelling is again observed in direct association with the basolateral plasma membrane. Gold particles are 10 nm. (I) FPN1 and kidney electrogenic Na-bicarbonate cotransporter-1 (NBCe1-A) immunoreactivity in rat kidney cortex. Homogenate, microsomal membranes and BLM from rat kidney cortex were separated under reducing conditions by SDS-PAGE on an 8% acrylamide gel. The blot was incubated with anti-rat FPN1 or anti-rat NBCe1-A (1:500). Characteristic bands at ∼60 and ∼130 kD for FPN1 and NBCe1-A were detected. Sizes (in kilodaltons) of molecular mass markers are indicated on the left.

Mentions: To visualize the exact cellular location of FPN1 in kidney PT, we immunostained kidneys using Liu-FPN1. Immunoperoxidase staining showed that Liu-FPN1 strongly stained PTs in the kidney cortex. Staining was absent from glomeruli and distal tubules (Fig. 2A). At higher magnification, FPN1 immunoreactivity was observed on the basal membrane and what appeared to be the inside of PT cells (Fig. 2B and C). This pattern of staining was evident in the S1, S2 and S3 segments of the PT (Fig. 2D and E). Staining appeared to be most prominent in the S2 segments, weaker in S1 segments and weakest in S3 segments.


Ferroportin 1 is expressed basolaterally in rat kidney proximal tubule cells and iron excess increases its membrane trafficking.

Wolff NA, Liu W, Fenton RA, Lee WK, Thévenod F, Smith CP - J. Cell. Mol. Med. (2011)

Immunoperoxidase labelling of Liu-FPN1 in rat kidney. (A) Strong labelling is evident throughout the cortex and outer stripe of the outer medulla. Labelling is associated with tubule segments morphologically resembling PTs. No staining is observed in glomeruli or vasculature. (B) At high magnification, labelling is predominantly BLM associated, with some intracellular staining. (C) and (D) Labelling is strongest in the S1 and S2 segments, whilst weaker labelling is observed in the S3 segment (E). T, thick ascending limb; G, glomerulus. Immunogold electron microscopy of Liu-FPN1 in rat kidney. (F) In PT S1 segments (note the long, extensive invaginations of the basolateral plasma membrane), immunogold labelling of FPN1 is observed throughout the cells basolateral plasma membrane domains (arrows). (G) At high magnification FPN1 can be observed in direct association with the plasma membrane. (H) In PT S2 segments (note the numerous small lateral processes at the base of the cell), labelling is again observed in direct association with the basolateral plasma membrane. Gold particles are 10 nm. (I) FPN1 and kidney electrogenic Na-bicarbonate cotransporter-1 (NBCe1-A) immunoreactivity in rat kidney cortex. Homogenate, microsomal membranes and BLM from rat kidney cortex were separated under reducing conditions by SDS-PAGE on an 8% acrylamide gel. The blot was incubated with anti-rat FPN1 or anti-rat NBCe1-A (1:500). Characteristic bands at ∼60 and ∼130 kD for FPN1 and NBCe1-A were detected. Sizes (in kilodaltons) of molecular mass markers are indicated on the left.
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Related In: Results  -  Collection

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fig02: Immunoperoxidase labelling of Liu-FPN1 in rat kidney. (A) Strong labelling is evident throughout the cortex and outer stripe of the outer medulla. Labelling is associated with tubule segments morphologically resembling PTs. No staining is observed in glomeruli or vasculature. (B) At high magnification, labelling is predominantly BLM associated, with some intracellular staining. (C) and (D) Labelling is strongest in the S1 and S2 segments, whilst weaker labelling is observed in the S3 segment (E). T, thick ascending limb; G, glomerulus. Immunogold electron microscopy of Liu-FPN1 in rat kidney. (F) In PT S1 segments (note the long, extensive invaginations of the basolateral plasma membrane), immunogold labelling of FPN1 is observed throughout the cells basolateral plasma membrane domains (arrows). (G) At high magnification FPN1 can be observed in direct association with the plasma membrane. (H) In PT S2 segments (note the numerous small lateral processes at the base of the cell), labelling is again observed in direct association with the basolateral plasma membrane. Gold particles are 10 nm. (I) FPN1 and kidney electrogenic Na-bicarbonate cotransporter-1 (NBCe1-A) immunoreactivity in rat kidney cortex. Homogenate, microsomal membranes and BLM from rat kidney cortex were separated under reducing conditions by SDS-PAGE on an 8% acrylamide gel. The blot was incubated with anti-rat FPN1 or anti-rat NBCe1-A (1:500). Characteristic bands at ∼60 and ∼130 kD for FPN1 and NBCe1-A were detected. Sizes (in kilodaltons) of molecular mass markers are indicated on the left.
Mentions: To visualize the exact cellular location of FPN1 in kidney PT, we immunostained kidneys using Liu-FPN1. Immunoperoxidase staining showed that Liu-FPN1 strongly stained PTs in the kidney cortex. Staining was absent from glomeruli and distal tubules (Fig. 2A). At higher magnification, FPN1 immunoreactivity was observed on the basal membrane and what appeared to be the inside of PT cells (Fig. 2B and C). This pattern of staining was evident in the S1, S2 and S3 segments of the PT (Fig. 2D and E). Staining appeared to be most prominent in the S2 segments, weaker in S1 segments and weakest in S3 segments.

Bottom Line: FPN1 was found to be located in association with the basolateral PT membrane and within the cytosolic compartment.These data support a role for FPN1 in vectorial export of iron out of PT cells.Furthermore, under conditions of iron loading of cultured PT cells, FPN1 was trafficked to the plasma membrane suggesting a coordinated cellular response to export excess iron and limit cellular iron concentrations.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology & Pathophysiology, University of Witten/Herdecke, Witten, Germany.

Show MeSH
Related in: MedlinePlus