Role of estrogen receptors, PKC and Src in ERK2 and p38 MAPK signaling triggered by 17β-estradiol in skeletal muscle cells

We have previously reported in C2C12 murine skeletal muscle cells that 10(-8) M 17 beta-estradiol promotes MAPKs stimulation which in turn mediates the activation of CREB and Elk-1 transcription factors. In this work, we demonstrated that the hormone induces ERK2 phosphorylation (without affecting ERK1 activation) and also stimulates p38 MAPK, both in a dose-dependent manner. Moreover, estrogen receptors involvement in MAPKs activation by the estrogen was studied. The use of ICI182780 (1 mu M), antagonist of ERs, and specific siRNAs to block ER alpha and ER beta expression, demonstrated that ER alpha mediates ERK2 activation but not p38 MAPK phosphorylation by 17 beta-estradiol, and that ER beta isoform is not implicated in MAPKs activation by the hormone. Furthermore, Src and PKC contribution in estrogen stimulation of the MAPKs was investigated. Compounds PP2 and Ro318220. Src and PKC family inhibitors, respectively abrogated ERK2 and p38 MAPK phosphorylation by 17 beta-estradiol. Of interest, the hormone was able to induce Src and PKC delta activation. In addition, Ro318220 decreased estrogen-dependent Src modulation implicating PKC in hormone upregulation of Src. Accordingly, PP2 and Ro318220 suppressed CREB and Elk-1 phosphorylation as well as c-Fos and c-Jun oncoprotein levels induced by 17 beta-estradiol. Altogether, these data indicate that 17 beta-estradiol activates ERK2 through ER alpha and p38 MAPK in an ER alpha/beta-independent manner and that PKC and Src proteins are key upstream components on MAPKs activation in C2C12 skeletal muscle cells. (C) 2010 Elsevier Ltd. All rights reserved.