Etude de l'implication du système protéolytique calcium dépendant dans la migration de la cellule myogénique

Soutenue le 5 juillet 2005 Diplôme : Dr. d'Universit

Interaction(s) MARCKS/Protéolyse calcium dépendante lors de la migration des myoblastes

National audienc

Calcium dependent proteolysis and muscle cell motility

National audienc

Régulation de la migration des cellules musculaires par le système protéolytique neutre-calcium dépendant

National audienc

Involvement of calpains in growth factor-mediated migration

International audienc

Involvement of the ERK/MAP kinase signalling pathway in milli-calpain activation and myogenic cell migration

International audienc

Involvement of calpains in growth factor-mediated migration

International audiencePrevious research in our laboratory has already shown the importance of the role played by ubiquitous calpains during myoblast migration. The aim of this study was to investigate calpain expression during myoblast migration and, to enhance this phenomenon via calpain stimulation. Ubiquitous calpains are members of a large family of calcium-dependent cysteine proteases. They play an important role in numerous biological and pathological phenomena, such as signal transduction, apoptosis, cell-cycle regulation, cell spreading, adhesion, invasion, myogenesis, and motility. Myoblast migration is a crucial step in myogenesis, as it is necessary for myoblast alignment and fusion to form myotubes. This study started by examining changes in calpain expression during migration, then investigated the possibility of activating myoblast migration via the stimulation of calpain expression and/or activity. The migration rate of myoblasts overexpressing mu- or milli-calpain was quantified. The results showed that calpain overexpression dramatically inhibited myoblast migration. Growth-factor treatments were then used to enhance myoblast migration. The results showed that treatment with IGF-1, TGF-beta1, or insulin induced a major increase in migration and caused a significant increase in m-calpain expression and activity. The increase in migration was totally inhibited by adding calpeptin, a calpain-specific inhibitor. These findings suggest that milli-calpain is involved in growth factor-mediated migration

Myoblast attachment and spreading are regulated by different patterns by ubiquitous calpains

International audienceThe calcium-dependent proteolytic system is a large family of well-conserved ubiquitous and tissue-specific proteases, known as calpains, and an endogenous inhibitor, calpastatin. Ubiquitous calpains are involved in many physiological phenomena, such as the cell cycle, muscle cell differentiation, and cell migration. This study investigates the regulation of crucial steps of cell motility, myoblast adhesion and spreading, by calpains. Inhibition of each ubiquitous calpain isoform by antisense strategy pinpointed the involvement of each of these proteases in myoblast adhesion and spreading. Moreover, the actin cytoskeleton and microtubules were observed in transfected cells, demonstrating that each ubiquitous calpain could be involved in the actin fiber organization. C2C12 cells with reduced mu- or m-calpain levels have a rounded morphology and disorganized stress fibers, but no modification in the microtubule cytoskeleton. Antisense strategy directed against MARCKS, a calpain substrate during C2C12 migration, showed that this protein could play a role in stress fiber polymerization. A complementary proteomic analysis using C2C12 cells over-expressing calpastatin indicated that two proteins were under-expressed, while six, which are involved in the studied phenomena, were overexpressed after calpain inhibition. The possible role of these proteins in adhesion, spreading, and migration was discussed

Myoblast attachment and spreading are regulated by different patterns by ubiquitous calpains

April 2006 International audienc

Implication de la protéolyse calcium-dépendante lors de l'adhésion et de la migration des cellules myogéniques

National audienc