S-PALMITOYLATION CONTROLS ESTROGEN RECEPTOR a ASSOCIATION WITH CAVEOLIN-1 AND CELL CYCLE PROGRESSION

Estrogen receptor (ER)a-mediated rapid events are now defined as necessary and sufficient for 17b-estradiol (E2)-induced cell cycle-regulating genes (e.g., cyclin D1) and G1/S phase transition. These actions are thought to require a plasma membrane ERa. We postulated that S-palmitoylation of the Cys447 residue may explain the ability of ERa to associate to plasma membrane making possible E2-dependent rapid functions. Cell lines expressing transfected or endogenous human ERa (HeLa and HepG2, respectively) or the ERa non-palmitoylable Cys447Ala mutant transfected in HeLa cells have been used as experimental models. Here, we report direct evidence that ERa is a palmitoylated protein. The mutation of the Cys447 residue to Ala impairs ERa palmitoylation and results in the loss of ERa plasma membrane localization and interaction with caveolin-1. In turn, E2-induced rapid non-genomic signals (i.e., ERK and AKT activation, cyclin D1 promoter activity and DNA synthesis) are also prevented. On the other hand, the Cys447Ala mutation significantly decreases the E2-induced transactivation of an estrogen responsive element construct probe. Remarkably, both ERa palmitoylation and its interaction with caveolin-1 are reduced by E2 in time and dose dependent fashion. Similar results have been obtained in HepG2 cells. As a whole, these data indicate that palmitoylation can be regarded as a regulatory device enabling ERa to initiate non genomic signal transduction pathways that lead cell to proliferate.