Analysis of the androgen receptor/filamin a complex in stromal cells.

The androgen receptor (AR), a ligand-regulated nuclear transcription factor, mediates differentiation and proliferation of target tissues. Its action is frequently associated with human proliferative diseases, mainly the prostate cancer. We have recently analyzed in mouse embryo NIH3T3 fibroblasts and human fibrosarcoma HT1080 cells the molecular basis and the biological role of AR interaction with the full-length filamin A (FLNa), an actin-cross-linking protein. Here, we describe a procedure revealing the AR/FLNa complex in stromal cells. Upon physiological (10 nM) androgen stimulation of quiescent NIH3T3 cells, FLNa co-immunoprecipitates with AR and co-localizes with the receptor at intermediate actin filaments. The AR/FLNa complex specifically regulates AR extranuclear functions leading to Rac1 activation and consequent cell motility. This complex adds a new and unexpected piece to the growing evidence of the role of signalling effectors, scaffolds, and cytoskeletal proteins in the rapid androgen action and in progression of hormone-dependent cancers.