Acetylation modulates prolactin receptor dimerization

Cytokine-activated receptors undergo extracellular domain dimerization, which is necessary to activate intracellular signaling pathways. Here, we report that in prolactin (PRL)-treated cells, PRL receptor (PRLR) undergoes cytoplasmic loop dimerization that is acetylation-dependent. PRLR-recruited CREB-binding protein (CBP) acetylates multiple lysine sites randomly distributed along the cytoplasmic loop of PRLR. Two PRLR monomers appear to interact with each other at multiple parts from the membrane-proximal region to the membrane-distal region, relying on the coordination among multiple lysine sites neutralized via acetylation. Cytoplasmic loop-dimerized PRLR activates STAT5, which is also acetylated by CBP and undergoes acetylation-dependent dimerization. PRLR dimerization and subsequent signaling are enhanced by treating the cells with deacetylase sirtuin (SIRT) inhibitor nicotinamide or histone deacetylase (HDAC) inhibitor trichostatin A but inhibited by expressing exogenous deacetylase SIRT2 or HDAC6. Our results suggest that acetylation and deacetylation provide the rheostatlike regulation for the cytokine receptor PRLR in its cytoplasmic loop dimerization and subsequent STAT5 activation.