Protective role of calreticulin in HFE hemochromatosis.
HFE gene mutations are associated with over 80% of cases of hereditary hemochromatosis (HH), an iron-overload disease in which the liver is the most frequently affected organ. Research on HFE has traditionally focused on its interaction with the transferrin receptor. More recent studies have suggested a more complex function for this nonclassical MHC-I protein. The aim of this study was to examine how HFE and its two most common mutations affect the expression of selected genes in a hepatocyte-like cell line. Gene expression was analyzed in HepG2 cells overexpressing wild-type and mutant HFE. The effect of HFE in iron import and oxidative stress levels was assessed. Unfolded protein response (UPR)-activated gene expression was analyzed in peripheral blood mononuclear cells from characterized HH patients. C282Y HFE down-regulated hepcidin and enhanced calreticulin mRNA expression. Calreticulin levels correlated with intracellular iron increase and were associated with protection from oxidative stress. In C282Y(+/+) patients calreticulin levels correlated with the expression of the UPR marker BiP and showed a negative association with the number of hereditary hemochromatosis clinical manifestations. The data show that expression of C282Y HFE triggers a stress-protective response in HepG2 cells and suggest a role for calreticulin as a modifier of the clinical expression of HH.
Pinto
Jorge P
JP
Iron Genes and Immune System, Instituto de Biologia Molecular e Celular, Universidade do Porto, 4150-180 Porto, Portugal.
Ramos
Pedro
P
de Almeida
Sérgio F
SF
Oliveira
Susana
S
Breda
Laura
L
Michalak
Marek
M
Porto
Graça
G
Rivella
Stefano
S
de Sousa
Maria
M
D000328:Adult; D000368:Aged; D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000235:genetics / Q000378:metabolism; D037282:Calreticulin / Q000037:antagonists & inhibitors / Q000097:blood* / Q000235:genetics*; D002460:Cell Line; D004195:Disease Models, Animal; D005260:Female; D005786:Gene Expression Regulation; D006432:Hemochromatosis / Q000235:genetics* / Q000503:physiopathology; D000071020:Hemochromatosis Protein; D022781:Hepatocytes / Q000378:metabolism / Q000473:pathology; D064451:Hepcidins; D015395:Histocompatibility Antigens Class I / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism*; D051379:Mice; D008875:Middle Aged; D009000:Monocytes / Q000378:metabolism / Q000473:pathology; D020125:Mutation, Missense; D018384:Oxidative Stress; D012333:RNA, Messenger / Q000032:analysis; D034741:RNA, Small Interfering / Q000008:administration & dosage; D051381:Rats; D011990:Receptors, Transferrin / Q000096:biosynthesis / Q000097:blood / Q000235:genetics; D014162:Transfection
D023181:Antimicrobial Cationic Peptides; D037282:Calreticulin; C578702:HAMP protein, human; C103673:HFE protein, human; C579599:Hamp protein, mouse; C578703:Hamp protein, rat; D000071020:Hemochromatosis Protein; D064451:Hepcidins; D015395:Histocompatibility Antigens Class I; D008565:Membrane Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D011990:Receptors, Transferrin