PPP1R1B

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Protein phosphatase 1 regulatory subunit 1B (PPP1R1B), also known as dopamine- and cAMP-regulated neuronal phosphoprotein (DARPP-32), is a protein that in humans is encoded by the PPP1R1B gene. Midbrain dopaminergic neurons play a critical role in multiple brain functions, and abnormal signaling through dopaminergic pathways has been implicated in several major neurologic and psychiatric disorders. One well studied target for the actions of dopamine is DARPP32. In the densely dopamine- and glutamate-innervated rat caudate-putamen, DARPP32 is expressed in medium-sized spiny neurons that also express dopamine D1 receptors. The function of DARPP32 seems to be regulated by receptor stimulation. Both dopaminergic and glutamatergic (NMDA) receptor stimulation regulate the extent of DARPP32 phosphorylation, but in opposite directions. Dopamine D1 receptor stimulation enhances cAMP formation, resulting in the phosphorylation of DARPP32; (this is disputed by more recent research that claims cAMP signaling induces dephosphorylation of DARPP32) phosphorylated DARPP32 is a potent protein phosphatase-1 (PPP1CA) inhibitor. NMDA receptor stimulation elevates intracellular calcium, which leads to activation of calcineurin and dephosphorylation of phospho-DARPP32, thereby reducing the phosphatase-1 inhibitory activity of DARPP32. DARPP-32 is critical for dopamine dependent striatal synaptic plasticity, possibly by serving as a dopamine-dependent gating mechanism for calcium/CaMKII signaling. It has been predicted that DARPP-32, in conjunction with ARPP-21, could also be involved in setting-up of eligibility trace-like temporal window for striatal postsynaptic signaling.