Regulation of the Ca2+Channel CaV1.2 Supports Spatial Memory and Its Flexibility and LTD

Abstract

Widespread release of norepinephrine (NE) throughout the forebrain fosters learning and memory via adrenergic receptor (AR) signaling, but the molecular mechanisms are largely unknown. The β2AR and its downstream effectors, the trimeric stimulatory Gs-protein, adenylyl cyclase (AC), and the cAMP-dependent protein kinase A (PKA), form a unique signaling complex with the L-type Ca2+channel (LTCC) CaV1.2. Phosphorylation of CaV1.2 by PKA on Ser1928is required for the upregulation of Ca2+influx on β2AR stimulation and long-term potentiation induced by prolonged theta-tetanus (PTT-LTP) but not LTP induced by two 1-s-long 100-Hz tetani. However, the function of Ser1928phosphorylationin vivois unknown. Here, we show that S1928A knock-in (KI) mice of both sexes, which lack PTT-LTP, express deficiencies during initial consolidation of spatial memory. Especially striking is the effect of this mutation on cognitive flexibility as tested by reversal learning. Mechanistically, long-term depression (LTD) has been implicated in reversal learning. It is abrogated in male and female S1928A knock-in mice and by β2AR antagonists and peptides that displace β2AR from CaV1.2. This work identifies CaV1.2 as a critical molecular locus that regulates synaptic plasticity, spatial memory and its reversal, and LTD.SIGNIFICANCE STATEMENTWe show that phosphorylation of the Ca2+channel CaV1.2 on Ser1928is important for consolidation of spatial memory and especially its reversal, and long-term depression (LTD). Identification of Ser1928as critical for LTD and reversal learning supports the model that LTD underlies flexibility of reference memory.