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Title
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The SLC40A1 R178Q mutation is a recurrent cause of hemochromatosis and is associated with a novel pathogenic mechanism
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Author
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Abstract
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| Hemochromatosis type 4 is one of the most common causes of primary iron overload, after I/Fr-related h.emochromatosis. It is an autosomal dominant disorder, primarily due to missense mutations in S.I.C40A1. This gene encodes ferroportin 1 (FPN1), which is the sole iron export protein reported in mammals. Not all heterozygous missense mutations in SLC40/11 are disease-causing. Due to phenocopies and an increased demand for genetic testing, rare SLC40/11 variations are fortuitously observed in patients with a secondary cause of hyperferritinemia. Structure/function analysis is the most effective way of establishing causality when clinical and segregation data are lacking. It can also provide important insights into the mechanism of iron egress and FPN1 regulation by hepcidin. The present study aimed to determine the pathogenicity of the previously reported p.Arg178GIn variant. We present the biological, clinical, histological and radiological findings of 22 patients from six independent families of French, Belgian or Iraqi decent. Despite phenotypic variability, all patients with pArg178GIn had elevated serum ferritin concentrations and normal to low transferrin saturation levels. In vitro experiments demonstrated that the p.Arg178G.In mutant reduces the ability of FPN1 to export iron without causing protein mislocalization. Based on a comparative model of the 3D structure of human FP.N1 in an outward facing conformation, we argue that pArg178 is part of an interaction network modulating the conformational changes required for iron transport. We conclude that p.Arg178GIn represents a new category of loss-of-function mutations and that the study of 'gating residues" is necessa.ry in order to fully understand the action mechanism of FPN1. |
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Language
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English
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Source (journal)
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Haematologica. - Roma
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Publication
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Roma
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2018
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ISSN
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0390-6078
1592-8721
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DOI
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10.3324/HAEMATOL.2018.189845
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Volume/pages
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103
:11
(2018)
, p. 1796-1805
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ISI
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000451732200022
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Pubmed ID
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30002125
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Full text (Publisher's DOI)
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Full text (open access)
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