ARPP-21

ARPP-21, also known as cAMP-regulated phosphoprotein 21 kDa, is a protein found in the mammalian brain. It is a substrate for cAMP-dependent protein kinase (PKA) and protein phosphatase 2B (calcineurin). Phosphorylation and dephosphorylation of ARPP-21 regulate its activity, affecting intracellular signaling pathways involved in neuronal function. Specifically, when phosphorylated by PKA, ARPP-21 becomes an inhibitor of protein phosphatase 2A (PP2A), a key enzyme involved in dephosphorylating a wide range of proteins. Through this mechanism, ARPP-21 plays a role in modulating the phosphorylation state of numerous target proteins, ultimately impacting synaptic plasticity, learning, and memory processes. The precise function of ARPP-21 is complex and still under investigation, but studies suggest its involvement in dopamine signaling and neuronal excitability.