Rapid membrane effect of testosterone in LNCaP cells

Testosterone signaling is widely considered to be mediated through the transcription-regulating intracellular androgen receptor (iAR). In the human prostate cancer cell line LNCaP we demonstrated the presence of unconventional membrane receptors for testosterone (mAR) besides the classic iAR. Binding sides for testosterone on the surface of LNCaP cells were clearly revealed with the membrane-impermeable testosterone-BSA-FITC by confocal laser-scanning microscopy and flow cytometry. Furthermore, we found that testosterone was able to induce a rapid activation of extracellular signal-related kinase 1 and 2 (ERK1/2), but not altered p38 MAPK and c-jun N-terminal kinase (JNK) activity. The testosterone-induced phosphorylation of ERK1/2 could not be inhibited by the AR antagonist cyproterone, excluding the involvement of iAR. Consistent with this finding, the impeded testosterone-BSA was also capable of rapidly phosphorylating ERK1/2, further revealing membrane receptor being responsible for the activation of ERK1/2. Additionally, testosterone-BSA induced a transient expression of c-Fos, which was in a timescale consistent with the rapid ERK1/2 phosphorylation and could be blocked by ERK1/2 inhibitor PD098059, suggesting an ERK1/2-dependent mechanism. Together, these data demonstrated a novel mode of testosterone signaling on LNCaP cells which was not mediated through the classical androgen receptor response, but through unconventional membrane receptors.