Rac1 and RhoA GTPases have antagonistic functions during N-cadherin-dependent cell-cell contact formation in C2C12 myoblasts.
BACKGROUND
N-cadherin, a member of the Ca(2+)-dependent cell-cell adhesion molecule family, plays an essential role in the induction of the skeletal muscle differentiation programme. However, the molecular mechanisms which govern the formation of N-cadherin-dependent cell-cell contacts in myoblasts remain unexplored.


RESULTS
In the present study, we show that N-cadherin-dependent cell contact formation in myoblasts is defined by two stages. In the first phase, N-cadherin is highly mobile in the lamellipodia extensions between the contacting cells. The second stage corresponds to the formation of mature N-cadherin-dependent cell contacts, characterized by the immobilization of a pool of N-cadherin which appears to be clustered in the interdigitated membrane structures that are also membrane attachment sites for F-actin filaments. We also demonstrated that the formation of N-cadherin-dependent cell-cell contacts requires a co-ordinated and sequential activity of Rac1 and RhoA. Rac1 is involved in the first stage and facilitates N-cadherin-dependent cell-cell contact formation, but it is not absolutely required. Conversely, RhoA is necessary for N-cadherin-dependent cell contact formation, since, via ROCK (Rho-associated kinase) signalling and myosin 2 activation, it allows the stabilization of N-cadherin at the cell-cell contact sites.


CONCLUSIONS
We have shown that Rac1 and RhoA have opposite effects on N-cadherin-dependent cell-cell contact formation in C2C12 myoblasts and act sequentially to allow its formation.
Comunale
Franck
F
CRBM, CNRS, 1919 Route de Mende, 34293 Montpellier, France.
Causeret
Marie
M
Favard
Cyril
C
Cau
Julien
J
Taulet
Nicolas
N
Charrasse
Sophie
S
Gauthier-Rouvière
Cécile
C
D015820:Cadherins / Q000187:drug effects / Q000378:metabolism*; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D006801:Humans; D032446:Myoblasts / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000502:physiology*; D020742:rhoA GTP-Binding Protein / Q000502:physiology*
D015820:Cadherins; C107953:RAC1 protein, human; D020830:rac1 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein