Association of estrogen receptor a and histone deacetylase 6 causes rapid deacetylation of tubulin in breast cancer cells

Estrogen receptor a (ERa) is a nuclear receptor that functions as a ligand-activated transcription factor. Besides its genomic action in nuclei, ERa could exert nongenomic actions at theplasma membrane. To investigate the mechanism underlyingthe nongenomic action of ERa in breast cancer cells, we generated a construct of membrane-targeted ERa (memER),an expression vector of ERa without the nuclear localizingsignal and including instead the membrane-targeting sequence of Src kinase. MemER was stably expressed in humanbreast cancer MCF-7 cells. Cell migration test and tumorigenicassay in nude mice revealed that the in vitro motility and the in vivo proliferation activity of MCF-7 cells expressing memER were significantly enhanced compared with those of vector-transfected cells. Interestingly, the acetylation level of tubulin in memER-overexpressing cells was lower than that in control cells. We found that histone deacetylase (HDAC) 6 translocated to the plasma membrane shortly after estrogen stimulation, and rapid tubulin deacetylation subsequently occurred. We also showed that memER associated with HDAC6 in a ligand-dependent manner. Although tamox- ifen is known for its antagonistic role in the ERa genomic action in MCF-7 cells, the agent showed an agonistic function in the memER-HDAC6 association and tubulin deacetylation. These findings suggest that ERa ligand dependently forms a complex with HDAC6 and tubulin at the plasma membrane. Estrogen-dependent tubulin deacetylation could provide new evidence for the nongenomic action of estrogen, which potentially contributes to the aggressiveness of ERa-positive breast cancer cells.