Analysis of estrogen receptor a signaling complex at the plasma membrane

There is accumulating evidence that the estrogen receptor (ER) can transduce specific signals at the plasma membrane. We tried to clarify the biological function of ER as a signaling molecule by identifying proteins that interact with the membrane-localized ER. The AF-1 and AF-2 domains of ER alpha with or without the membrane-targeting sequence were stably expressed in the breast cancer cell line, MCF-7. alpha- and beta-tubulins and heat shock protein 70 were identified as the AF-1-associated proteins. Of these, tubulins are associated only with membrane-targeted AF-1.