Localization of the iron-regulatory proteins hemojuvelin and transferrin receptor 2 to the basolateral membrane domain of hepatocytes.
The newly discovered proteins hemojuvelin (Hjv) and transferrin receptor type 2 (TfR2) are involved in iron metabolism. Mutations in the Hjv and TfR2 gene cause hemochromatosis. We investigated the expression and cellular localization of Hjv and TfR2 in rat and human liver. The expression of Hjv and TfR2 was shown on mRNA and protein level by RT-PCR and immunoblot experiments. Their cellular localization was studied by immunofluorescence with antibodies raised against Hjv and TfR2. Hjv and TfR2 are present in human and rat liver and in primary human hepatocytes. Antisera raised against Hjv identified immunoreactive proteins with an apparent size of 44 and 46 kDa in immunoblot experiments of rat and human liver extracts, which are in accordance with the putative membrane-bound and cleaved soluble forms of this protein, respectively. TfR2 was detected as a 105 kDa protein corresponding to the predicted size of glycosylated TfR2 monomers. In immunofluorescence experiments, Hjv and TfR2 were found in rat liver only in hepatocytes. At the subcellular level, both proteins were predominantly localized to the basolateral membrane domain of hepatocytes. The localization of Hjv and TfR2 at the same membrane domain renders a functional interaction of these two proteins in iron homeostasis possible.
Merle
Uta
U
Department of Gastroenterology, University Hospital, Heidelberg, Germany.
Theilig
Franziska
F
Fein
Evelyn
E
Gehrke
Sven
S
Kallinowski
Birgit
B
Riedel
Hans-Dieter
HD
Bachmann
Sebastian
S
Stremmel
Wolfgang
W
Kulaksiz
Hasan
H
D000818:Animals; D005455:Fluorescent Antibody Technique; D058851:GPI-Linked Proteins; D015870:Gene Expression; D006432:Hemochromatosis; D000071020:Hemochromatosis Protein; D022781:Hepatocytes / Q000737:chemistry* / Q000166:cytology / Q000648:ultrastructure; D006801:Humans; D015151:Immunoblotting; D008099:Liver / Q000737:chemistry*; D008565:Membrane Proteins / Q000032:analysis* / Q000235:genetics / Q000302:isolation & purification; D051381:Rats; D011990:Receptors, Transferrin / Q000032:analysis* / Q000235:genetics / Q000302:isolation & purification; D020133:Reverse Transcriptase Polymerase Chain Reaction
D058851:GPI-Linked Proteins; D000071020:Hemochromatosis Protein; C513726:Hjv protein, rat; D008565:Membrane Proteins; D011990:Receptors, Transferrin; C503640:TFR2 protein, human