TY - JOUR
T1 - Insulin promotes iron uptake in human hepatic cell by regulating transferrin receptor-1 transcription mediated by hypoxia inducible factor-1
AU - Biswas, Sudipta
AU - Tapryal, Nisha
AU - Mukherjee, Reshmi
AU - Kumar, Rajiv
AU - Mukhopadhyay, Chinmay K.
N1 - Funding Information:
This work is supported by grants from the Council of Scientific and Industrial Research and Indian council of Medical Research of India and Department of Science and Technology-PURSE program to CKM. SB acknowledges CSIR for Senior Research Fellowship. Mutant HIF-1α cDNA (P/A) was a kind gift from Dr. Ritu Kulshreshtha, Indian Institute of Technology, New Delhi, India.
PY - 2013/2
Y1 - 2013/2
N2 - Hepatic iron is known to regulate insulin signaling pathways and to influence insulin sensitivity in insulin resistance (IR) patients. However, the role of insulin on hepatic iron homeostasis remains unexplored. Here, we report that insulin promotes transferrin-bound iron uptake but shows no influence on non transferrin-bound iron uptake in human hepatic HepG2 cells. As a mechanism we detected increased transferrin receptor-1 (TfR1) expression both at protein and mRNA levels. Unaltered stability of protein and transcript of TfR1 suggested the regulation at transcriptional level that was confirmed by promoter activity. Involvement of transcription factor hypoxia inducible factor-1 (HIF-1) was shown by mutational analyses of the TfR1 promoter region and by electrophoretic mobility shift assay. When HepG2 cells were transfected with specific siRNA targeted to 3'UTR of HIF-1α, the regulatory subunit of HIF-1; insulin-induced TfR1 expression and iron uptake were inhibited. Transfection of cDNA expressing stable form of HIF-1α reversed the increased TfR1 expression and iron uptake. These results suggest a novel role of insulin in hepatic iron uptake by a HIF-1 dependent transcriptional regulation of TfR1.
AB - Hepatic iron is known to regulate insulin signaling pathways and to influence insulin sensitivity in insulin resistance (IR) patients. However, the role of insulin on hepatic iron homeostasis remains unexplored. Here, we report that insulin promotes transferrin-bound iron uptake but shows no influence on non transferrin-bound iron uptake in human hepatic HepG2 cells. As a mechanism we detected increased transferrin receptor-1 (TfR1) expression both at protein and mRNA levels. Unaltered stability of protein and transcript of TfR1 suggested the regulation at transcriptional level that was confirmed by promoter activity. Involvement of transcription factor hypoxia inducible factor-1 (HIF-1) was shown by mutational analyses of the TfR1 promoter region and by electrophoretic mobility shift assay. When HepG2 cells were transfected with specific siRNA targeted to 3'UTR of HIF-1α, the regulatory subunit of HIF-1; insulin-induced TfR1 expression and iron uptake were inhibited. Transfection of cDNA expressing stable form of HIF-1α reversed the increased TfR1 expression and iron uptake. These results suggest a novel role of insulin in hepatic iron uptake by a HIF-1 dependent transcriptional regulation of TfR1.
KW - Hepatic iron overload
KW - Hypoxia inducible factor-1
KW - Insulin
KW - Iron uptake
KW - Transcription
KW - Transferrin receptor-1
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U2 - 10.1016/j.bbadis.2012.11.003
DO - 10.1016/j.bbadis.2012.11.003
M3 - Article
C2 - 23160040
AN - SCOPUS:84870975083
SN - 0925-4439
VL - 1832
SP - 293
EP - 301
JO - Biochimica et Biophysica Acta - Molecular Basis of Disease
JF - Biochimica et Biophysica Acta - Molecular Basis of Disease
IS - 2
ER -