The knowledge of therapeutic strategies able to counteract skeletal muscle atrophy is an important issue for human health. In previous studies, we have showed that b2-adrenoceptors (AR) activation regulates muscle protein metabolism through the suppression of the activity of ubiquitin (Ub)-proteasome system, the major proteolytic system involved in muscle wasting, and the expression of atrophy-related genes (atrogenes). Multiple signaling pathways, such as cAMP/PKA, ERK1/2 and Akt, have been associated with the antiproteolytic effects of b2-agonists. However, the precise molecular mechanism by which these kinases suppress atrogenes expression is unclear. Preliminary results from our lab indicate that pharmacological activation of b2AR induces acetylation, and possibly inactivation, of Foxo, a family of transcription factors responsible for atrogenes expression. Thus, the project aims to investigate the in vivo involvement of histone deacetilases (HDAC) and histone acetyltransferases (HAT) p300/CBP in Foxo acetylation and downregulation of atrophy gene program induced by b2-adrenergic signaling in skeletal muscle. For that, in vivo techniques of molecular biology, such as gene transfer by electroporation and the analysis of transcriptional factor activity by imaging system, will be implanted in our lab. Therefore, Foxo acetylation status will be able to be correlated with the in vivo transcriptional activity of Foxo and the expression level of atrogenes in atrophic muscles from 2-days-fasted mice treated with formoterol, a potent b2-agonist. To investigate further the signaling pathways involved in the anticatabolic action of b2-agonist, skeletal muscles will be transfected with dominant negative forms of PKA, CREB, ERK2 or Akt. In addition, we will test whether in vivo transfection of CREB and Sik1, a kinase downstream of CREB and an inhibitor of HDACs, is able to regulate the activity and the acetylation level of Foxo and prevent muscle wasting.
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