Phosphorylation states of DARPP-32. Differently shaded boxes show singly, doubly and triply phosphorylated states of DARPP-32, and labels indicate phosphorylation positions. Arrows indicate transitions between different phosphorylation forms through enzymatic reactions. Dash-dotted lines with bars represent inhibition. Abbreviations are: protein phosphatase-1 (PP1), protein kinase A (PKAc), dopamine- and cAMP-regulated phosphoprotein with 32 kDa molecular weight (DARPP-32). Different phosphorylation states of DARPP-32 are indicated by the corresponding amino acid(s) and location(s). For instance, (Thr34-Ser102) refers to DARPP-32 phosphorylated simultaneously at positions 34 and 102.