|M.Sc Student||Reubeni Mickol|
|Subject||Involvement of the Rho Protein in the Differentiation of|
Skeletal Muscle Cells
|Department||Department of Medicine||Supervisor||Professor Eyal Bengal|
In this study, we investigated
the involvement of RhoA protein in the differentiation of skeletal muscle
Rho GTPases belong to a subgroup of the Ras superfamily of 20-30 kD GTP-binding proteins. Rho is involved in a wide range of biological processes, yet there are very few works on its role in muscle cell differentiation.
We found that expression of the inactive form of RhoA inhibits the expression of several differentiation markers in C2 myoblasts. In addition inactivation of RhoA reduced the expression levels of p21 (cyclin dependent kinase inhibitor), which is known to protect myoblasts from apoptotisis, however, it did not affect the cells withdrawal from the cell cycle. Thus, we thought that RhoA might be involved in the differentiation of process also by preventing the apoptosis of differentiating myoblasts. This hypothesis was supported by an experiment in which inhibition of RhoA in C2 cells induced high proportion of myoblasts to undergo programmed cell death during differentiation. Several works suggested that PI3K is one of the effectors of Rho. Recently, it was shown that PI3K (Phosphoinositide 3 Kinase) and its downstream effector Akt induce the expression of p21 and maintain muscle cell survival. We found that inhibition of Rho reduced the amount of phosphorylated Akt, therefore we suggest that Akt is an effector of Rho in skeletal muscle cells.
We conclude that the RhoA protein, through different pathways, affects at least two processes occurring during differentiation: a) expression of muscle specific genes, b) protection of the differentiating myoblasts from apoptosis.