17betaestradiol exerts protective effects in skeletal muscle cells at the level of the apoptotic ASK1-MAP kinase pathway.

NOELIA ZANETTI; MILANESI, LORENA; BOLAND, RICARDO

New Orleans, USA,

Congreso; The American Society for Biochemistry and Molecular Biology (ASBMB).; 2009

ASBMB

17b-estradiol exerts  protective effects in skeletal muscle cells  at the level of the apoptotic ASK1-MAP kinase pathway Zanetti N. I., Milanesi L. M. and Boland R. L. Departamento de Biologia, Bioquimica y Farmacia, Universidad Nacional del Sur. San Juan 670, 8000 Bah¨ªa Blanca, Argentina. nzanetti@criba.edu.ar 17b-estradiol is a steroid hormone that promotes cell survival and prevents from apoptosis in a great variety of tissues. Previous investigations with the murine skeletal muscle C2C12 cell line demonstrated that the action of 17b-estradiol involves stimulation of PI3K-Akt. Studies with other cell types have shown that upon its activation Akt can inhibit apoptosis by alternative mechanisms. In this report, we investigated whether the antiapoptotic effect of estrogen in muscle cells is mediated by Akt through interaction and dephosphorylation at Thr 845 of ASK-1, a MAPKKK pro-apoptotic protein. When proliferating C2C12 cells were treated with 17b-estradiol (10-8 M), phosphorylation of ASK1 (Thr 845) and JNK was decreased. However, no significant changes occurred in ASK1 and JNK 1/2 protein levels. On the other hand, treatment with the apoptic agent H2O2 caused a sustained (30 min , 24 h) increase in ASK1 levels and phosphorylation at Thr 845 (associated to stimulation of kinase activity) and, in addition, of JNK 1/2 phosphorylation. Furthermore, a 17b-estradiol-dependent interaction between p-Akt and ASK1 was detected by coimmunoprecipitation. The association of both proteins was diminished by H2O2. In conclusion, these results suggest that Akt interaction with ASK1 followed by dephosphorylation of the latter is part of the mechanism by which 17b-estradiol exerts its antiapoptotic action in skeletal muscle cells challenged with stress stimuli.