Back to search form

Structural and molecular basis for the dysfunction of the selenium containing protein SelN in congenital muscular dystrophies

Research unit

UPR 9002 - Architecture et réactivité de l'ARN (IBMC)
15, rue Rene Descartes 67084 - Strasbourg Cedex

Group

Name: Régulations post-transcriptionnelles et nutrition

Group leader: LESCURE Alain - a.lescure@ibmc-cnrs.unistra.fr

Group leader's phone: 03 88 41 71 06

Website: Visit website

Group organization:
- Chercheurs: 2
- ITA: 1
- Doctorants: 1
- Post-Docs: 0
- Autres: 2

Publications of the team linked to the topic (3 last years):
1) Castets, P., Beuvin, M., Ferry, A., Le Grand, F., Castets, M., Chazaud, A., Rederstorff, M., Krol, A., Lescure, A., Romero, Guicheney, P. and Allamand, V. (2011) “Satellite loss and impaired muscle regeneration in Selenoprotein N deficiency” Hum Mol Genet, 20, 694-704.
2) Rederstorff M., Castets P., Arbogast S., Lainé J., Vassilopoulos S., Beuvin M., Dubourg O., Vignaud A., Ferry A., Krol A., Allamand V., Guicheney P., Ferreiro A. and Lescure A. (2011) “Increased Muscle Stress-Sensitivity Induced by Selenoprotein N Inactivation in Mouse: A Mammalian Model for SEPN1-Related Myopathy” PLoS One, 6, e23094. Epub 2011 Aug 8
3) Lescure, A., Castets, P., Grunwald, D., Allamand, V. & Howard, M. (2012) "Selenoprotein N: Its role in disease" In Selenium :Its Molecular Biology and Role in Human Health 3d Edition, Hatfield, Berry, Gladyshev Edt. Springer Verlag. 283-299

About PhD

PhD Director: LESCURE Alain - a.lescure@ibmc-cnrs.unistra.fr

Phone: 03 88 41 71 06

Junior advisor: non

Co-tutely: oui

Co-Director: non

About PhD topic :

Title: Structural and molecular basis for the dysfunction of the selenium containing protein SelN in congenital muscular dystrophies

Project: Studies conducted in our team concern the regulations of networks controlled by antioxidant reagents, such as selenium. Selenium is an essential trace element that has been linked to several diseases. It is found in a family of proteins in form of selenocysteine; this peculiar amino acid differs from cysteine by the single sulfur atom, which is replaced by selenium. Twenty-five so-called selenoproteins have been identified in human. They are mostly oxidoreductases involved numerous metabolic pathways linked to oxidative stress control. The presence of a selenocysteine residue in the catalytic site confers an increased reactivity.
Selenoprotein N (SelN) is a member of the selenium-containing protein family. It is an endoplasmic reticulum (ER) resident protein that is ubiquitously expressed in all tissues. However, the loss of function of the SEPN1 gene, which encodes SelN, leads to a selective set of muscular diseases in human (SEPN1-related myopathies), which suggests that, despite its widespread expression, SelN is particularly important in molecular processes relevant to muscle development and maintenance. Although the precise function of SelN remains unknown, the presence of a thioredoxin reductase motif in the core of the protein points to a redox function. In addition, its localization within the ER suggests that it is involved in one of the processes associated with this compartment, such as synthesis or modification of secreted proteins, lipid synthesis, calcium transport control during muscle contraction… However, substrate or cofactors specifically bound to SelN have not been identified so far.

A better understanding of SelN function is fundamental to deciphering the pathogenesis of SEPN1-related myopathies. Most importantly, the understanding of the mechanistic dysfunction(s) linked to SelN deficiency will open up avenues for the design of targeted therapeutic approaches.
The thesis project aims to conduct structural and molecular studies to address the catalytic activity of SelN and to analyze this activity in the context of cellular metabolic- or signaling-pathways, such as ER oxidative stress control, calcium homeostasis, or muscle function. X-ray crystallographic structural studies will be conducted in collaboration with a group at the Saarland University (Germany) in order to determine SelN 3D-structures. We will produce and purify recombinant SelN from several organisms in bacterial and yeast expression systems, initially taking advantage of the recent identification of a unique bacterial ortholog of SelN. These structures are expected to provide a basis for the determination of the amino acids of the active site and for the prediction of SelN molecular function. The 3D SelN structure might also help to interpret loss-of-function mutations identified in patients with SEPN1 related muscular dystrophy. Purified recombinant SelN protein will also be used to address structure-function relationship and to unravel SelN catalytic competence. Biochemical experiments will be undertaken to characterize molecular interactants by spectrophotometric titration of predicted substrates or cofactors based on analogies with other proteins described in the literature or others results obtained in the laboratory. These interactants will be further tested using in vitro enzymatic assays. Finally, cellular strategies will address SelN contribution to metabolic- or signaling-network. These results will next be integrated in a physiological context using an animal model for SEPN1 related muscular disease, mice invalided for the SEPN1 gene.

This collaborative project is developed in the framework of a joint binational M.Sc. program in Human and Molecular Biology between Saarland University and Strasbourg University.

Wished skills: Our mission is to discover new aspects of biology, in part to benefit human health and society. We will conduct our science openly and thoroughly, with passion and integrity. Most of all, I need you to have a positive experience doing science. Be curious, take some risks, and learn something new!
Contribution to this project requires good basic knowledge in structurale and molecular biology. Good english practice is alos reuqired for the interactions with our german collaborators.

Expertises which will be acquired during the training: Training will include differetn aspects linked to a research project, such as bibliographic studies, definition of the aims and experimental strategies, seting the experiences, critical analyses of results and reporting). Molecular and structural technics include: cloning - recombinant protein expression - chromatography purification - X-ray cristallography.