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Involvement of the Rho family GTPases in the signaling induced by mechanical stress and relaxation, hypergravity and simulated microgravity.(RHOGROUND)

Research project PX/7/LP/06 (Research action PX)

Persons :

  • Prof.  NUSGENS Betty - Université de Liège (ULG)
    Coordinator of the project
    Financed belgian partner
    Duration: 1/1/2003-31/12/2004

Description :

The loss of gravity as experienced during space flights causes systemic alterations in Man and animals that might be due to perturbations of the mechano-signaling. The aim of our programme is to understand the cellular and molecular mechanisms operating in the perception and transduction of mechanical signals, including gravity. Our ultimate goal is to disclose key-pathways that might represent potential targets for pharmacological intervention to prevent microgravity-related health alterations and similar diseases on earth.

During the STS-095 flight in the Shuttle Discovery (Oct. 1998), microgravity was shown to induce in fibroblasts a significant increase of IL-6 and MMP1 mRNA level. Morphological data (Guignandon et al., unpublished data) obtained by image analysis after immunolabeling of vinculin and phosphotyrosine demonstrated an alteration of the FA structure and phosphorylation. Altogether, these results suggest that cells interpret microgravity as stress relaxation.

The small G proteins of the Rho family (RhoA, Rac1 and Cdc42) are GDP/GTP-regulated binary switches that are involved in the control of highly diverse cellular processes. In particular, they are key-regulators of cytoskeleton organization, cell shape and movement, proliferation, gene expression as well as cell-cell and cell-matrix interactions. Our current research programme aims at evaluating the role of these signaling switches in the mechano-perception and -reaction. The strategy was to create fibroblastic cell lines (WI26) genetically engineered to express constitutively (QL) active or to suppress their expression by small interferential RNA (siRNA) (Deroanne et al., 2003 & 2004) and to use these cells in simulated microgravity models on ground

1. to create osteoblast cell lines (MG63) stably transfected at a unique locus with the constitutively active form (QL) of the RhoGTPases, RhoA, Rac1 and Cdc42,
2. to knock-down the RhoGTPases with their respective siRNA (KD ) in WI26 and MG63,
3. to determine the effects of the activation or suppression of the RhoGTPases on the cytoskeleton and focal contacts formation and architecture, and on various cell functions
4. the specific tasks will be to evaluate the effects of mechanical stress and relaxation, hypergravity and simulated microgravity on the non-transfected control cells (CO) and their genetically engineered (QL, KD) counterparts. Both early effects (cytoskeleton and focal adhesions and organization, activation and translocation of RhoGTPases, phosphorylation and nuclear translocation of signaling molecules, early genes expression, ...) and late effects (proliferation, apoptosis, collagen and fibronectin fibrillogenesis, expression of structural macromolecules and their degrading enzymes, cytokines and chemokines,...) will be considered.

These studies will bring new knowledge in the mechano-signaling pathways and in the mechanisms regulating the cellular reactions to the mechanical environment.
This project is a multinational research involving three international partners possessing a long standing expertise in space-biology (L. Vico et A. Guignandon, LBTO (St Etienne, France) and in cell-matrix and mechano-signaling field (M. Aumailley, Dpt Biochemistry, Cologne and T. Krieg and B. Eckes, Dpt Dermatology and Molecular Medicine, Cologne, Germany).

Satellite(s) or flight opportunity(ies):
- Clinostat (on-ground experiment)

Field of research:

Life Science: Cell Biology

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