Communicated by Segolène Ayme
Inactive matriptase-2 mutants found in IRIDA patients still repress hepcidin in a transfection assay despite having lost their serine protease activity†
Article first published online: 30 MAY 2012
© 2012 Wiley Periodicals, Inc.
Special Issue: Databases in Neurogenetics
Volume 33, Issue 9, pages 1388–1396, September 2012
How to Cite
Guillem, F., Kannengiesser, C., Oudin, C., Lenoir, A., Matak, P., Donadieu, J., Isidor, B., Méchinaud, F., Aguilar-Martinez, P., Beaumont, C., Vaulont, S., Grandchamp, B. and Nicolas, G. (2012), Inactive matriptase-2 mutants found in IRIDA patients still repress hepcidin in a transfection assay despite having lost their serine protease activity. Hum. Mutat., 33: 1388–1396. doi: 10.1002/humu.22116
- Issue published online: 13 AUG 2012
- Article first published online: 30 MAY 2012
- Accepted manuscript online: 11 MAY 2012 09:53AM EST
- Manuscript Accepted: 2 MAY 2012
- Manuscript Received: 19 DEC 2011
- ANR. Grant Number: 2009 RARE 007 01 and 2010 BLAN 1130 01
Mutations of the TMPRSS6 gene, which encodes Matriptase-2, are responsible for iron-refractory iron-deficiency anemia. Matriptase-2 is a transmembrane protease that downregulates hepcidin expression. We report one frameshift (p.Ala605ProfsX8) and four novel missense mutations (p.Glu114Lys, p.Leu235Pro, p.Tyr418Cys, p.Pro765Ala) found in IRIDA patients. These mutations lead to changes in both the catalytic and noncatalytic domains of Matriptase-2. Analyses of the mutant proteins revealed a reduction of autoactivating cleavage and the loss of N-Boc-Gln-Ala-Arg-p-nitroanilide hydrolysis. This resulted either from a direct modification of the active site or from the lack of the autocatalytic cleavage that transforms the zymogen into an active protease. In a previously described transfection assay measuring the ability of Matriptase-2 to repress the hepcidin gene (HAMP) promoter, all mutants retained some, if not all, of their transcriptional repression activity. This suggests that caution is called for in interpreting the repression assay in assessing the functional relevance of Matriptase-2 substitutions. We propose that Matriptase-2 activity should be measured directly in the cell medium of transfected cells using the chromogenic substrate. This simple test can be used to determine whether a sequence variation leading to an amino acid substitution is functionally relevant or not. Hum Mutat 33:1388–1396, 2012. © 2012 Wiley Periodicals, Inc.