Simultaneous Live Imaging of Multiple Endogenous Proteins Reveals a Mechanism for Alzheimer’s-Related Plasticity Impairment

Summary: CaMKIIα is a central mediator of bidirectional synaptic plasticity, including long-term potentiation (LTP) and long-term depression (LTD). To study how CaMKIIα movement during plasticity is affected by soluble amyloid-β peptide oligomers (Aβ), we used FingR intrabodies to simultaneously image endogenous CaMKIIα and markers for excitatory versus inhibitory synapses in live neurons. Aβ blocks LTP-stimulus-induced CaMKIIα accumulation at excitatory synapses. This block requires CaMKII activity, is dose and time dependent, and also occurs at synapses without detectable Aβ; it is specific to LTP, as CaMKIIα accumulation at inhibitory synapses during LTD is not reduced. As CaMKII movement to excitatory synapses is required for normal LTP, its impairment can mechanistically explain Aβ-induced impairment of LTP. CaMKII movement during LTP requires binding to the NMDA receptor, and Aβ induces internalization of NMDA receptors. However, surprisingly, this internalization does not cause the block in CaMKIIα movement and is observed for extrasynaptic, but not synaptic, NMDA receptors. : Cook et al. used simultaneous live imaging of multiple endogenous proteins to probe LTP- versus LTD-induced CaMKII trafficking to excitatory versus inhibitory synapses. They show that Aβ inhibits LTP by blocking LTP-induced CaMKII trafficking via signaling mechanisms that require CaMKII activity. Keywords: CaMKII, excitatory synapse, inhibitory synapse, trafficking, LTP, LTD, amyloid, FingR, intrabody, NMDA-receptor