Neurogranin, a link between calcium/calmodulin and protein kinase C signaling in synaptic plasticity

Abstract

Neurogranin (Ng) (also named RC3, p17 or BICKS) is a small protein originally identified in rat brain and abundantly expressed in several telencephalic areas, such as the cerebral cortex, hippocampus, amygdala, and striatum. In neurons, it is found concentrated at dendritic spines where it participates in synaptic signaling events through the regulation of calmodulin (CaM) availability. Ng features an IQ motif that mediates its interaction with CaM and phosphatidic acid (PA) and that is phosphorylated by protein kinase C (PKC) at serine 36 (Ser36). Ser36-phosphorylated Ng is unable to bind either CaM or PA. Ng knockout mice display an apparently normal phenotype; however, they show severe deficits in spatial and emotional learning and a decrease in LTP induction, mostly due to the attenuation of the signaling that depends on calcium/CaM kinase II (CaMKII), PKC, and protein kinase A (PKA) activation. The present review is an update on the most relevant information about Ng expression, localization, interactions, and modifications as well as on its role in synaptic plasticity.