tailieunhanh - Báo cáo khoa học: N-Glycosylation is important for the correct intracellular localization of HFE and its ability to decrease cell surface transferrin binding

HFE is a type 1 transmembrane protein that becomes N-glycosylated dur-ing transport to the cell membrane. It influences cellular iron concentra-tions through multiple mechanisms, including regulation of transferrin binding to transferrin receptors. The importance of glycosylation in HFE localization and function has not yet been studied. | N-Glycosylation is important for the correct intracellular localization of HFE and its ability to decrease cell surface transferrin binding Lavinia Bhatt1 Claire Murphy2 Liam Driscoll2 Maria Carmo-Fonseca3 Mary W. McCaffrey1 and John V. Fleming2 3 1 Department of Biochemistry Biosciences Institute University College Cork Ireland 2 Department of Biochemistry Schoolof Pharmacy and ABCRF University College Cork Ireland 3 Institute of Molecular Medicine University of Lisbon Portugal Keywords HFE N-glycosylation transferrin transferrin receptor 1 p2-microglobulin Correspondence J. V. Fleming Department of Biochemistry and Schoolof Pharmacy University College Cork Cork Ireland Fax 353 21 4901656 Tel 353 21 4901679 E-mail Note L. Bhatt and C. Murphy contributed equally to this work Received 8 February 2010 revised 14 May 2010 accepted 2 June 2010 doi HFE is a type 1 transmembrane protein that becomes N-glycosylated during transport to the cell membrane. It influences cellular iron concentrations through multiple mechanisms including regulation of transferrin binding to transferrin receptors. The importance of glycosylation in HFE localization and function has not yet been studied. Here we employed bioinformatics to identify putative N-glycosylation sites at residues N110 N130 and N234 of the human HFE protein and used site-directed mutagenesis to create combinations of single double or triple mutants. Compared with the wild-type protein which co-localizes with the type 1 transferrin receptor in the endosomal recycling compartment and on distributed punctae the triple mutant co-localized with BiP in the endoplasmic reticulum. This was similar to the localization pattern described previously for the misfolding HFE-C282Y mutant that causes type 1 hereditary haemachromatosis. We also observed that the triple mutant was functionally deficient in b2-microglobulin interactions and incapable of regulating transferrin binding .