Tyrosine-317 of p52^Shc mediates androgen-stimulated proliferation signals in human prostate cancer cells

The involvement of tyrosine phosphorylation signaling pathways in steroid-induced cell proliferation has received much attention. However, the adaptor molecule that mediates this interaction remains to be identified. In this communication, we identify p52^Shc as the mediator between tyrosine phosphorylation signaling and steroid signaling in steroid-responsive cell proliferation. Although the different LNCaP prostate cancer cells, C-33, C-51 and C-81, express similar levels of functional androgen receptor (AR), they exhibit different levels of androgen sensitivity. C-33 cell proliferation is highly responsive to the presence of androgens, whereas C-51 cell proliferation is comparatively less responsive to androgens. In contrast, C-81 cell proliferation is independent of androgens. In these cells, tyrosine phosphorylation levels of both p52^Shc and ErbB-2 were greatest in C-81 cells, comparatively less in C-51 cells and weaker in C-33 cells. The levels and activity of protein tyrosine phosphatase, cellular prostatic acid phosphatase, decreased correspondingly in those cells. In both androgen-independent, rapidly growing C-81 and ErbB-2 cDNA-transfected C-33 cells, p52^Shc was hyperphosphorylated at Tyr317 (Y317). Conversely, p52^Shc tyrophosphorylation was decreased in prostatic acid phosphatase cDNA-transfected stable subclones of C-81 cells, which restore androgen-sensitive proliferation and leads to slow growth rates. In C-33 cells, androgen-stimulated cell proliferation correlated with tyrophosphorylation of ErbB-2 and increased phosphorylation of p52^Shc at Y317, but not at Y239, differing from phosphorylation patterns associated with epidermal growth factor (EGF) stimulation. Furthermore, overexpression of a mutant of p52 ^Shc, that is Y317F, blocks Y317 phosphorylation of endogenous p52^Shc and abolishes androgen-stimulated proliferation, but not EGF-stimulated proliferation. Thus, Y317 of p52^Shc serves as an important regulatory site that allows tyrosine phosphorylation pathways to moderate androgen sensitivity in human prostate cancer cells.