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 rheostat-like regulation for the cytokine receptor PRLR in its cytoplasmic loop dimerization and subsequent STAT5 activation.