Photoactivatable CaMKII induces synaptic plasticity in single synapses

Abstract

Optogenetic approaches for studying neuronal functions have proven their utility in the neurosciences. However, optogenetic tools capable of inducing synaptic plasticity at the level of single synapses have been lacking. Here, we engineered a photoactivatable (pa)CaMKII by fusing a light-sensitive domain, LOV2, to CaMKIIα. Blue light or two-photon excitation reversibly activated paCaMKII. Activation in single spines was sufficient to induce structural long-term potentiation (sLTP) in vitro and in vivo. paCaMKII activation was also sufficient for the recruitment of AMPA receptors and functional LTP in single spines. By combining paCaMKII with protein activity imaging by 2-photon FLIM-FRET, we demonstrate that paCaMKII activation in clustered spines induces robust sLTP via a mechanism that involves the actin-regulatory small GTPase, Cdc42. This optogenetic tool for dissecting the function of CaMKII activation (i.e., the sufficiency of CaMKII rather than necessity) and for manipulating synaptic plasticity will find many applications in neuroscience and other fields.

Temporal pattern and synergy influence activity of ERK signaling pathways during L-LTP induction

“…L-LTP simulations using 1 µM amplitude calcium pulses produce similar ppERK traces for ITIs between 3 and 40 s ( Figure 7A ). Multiple 1 s pulses of 1 µM calcium are similar to a single 5 s pulse, due to the slow decay of pCaMKII; thus, calcium is above the threshold for CaMKII ultrasensitivity and ppERK is sustained for a long duration, consistent with experimental data showing that CaMKII above threshold is enough to induce L-LTP ( Shibata et al, 2021 ). Only with a 300 s ITI does pCaMKII and ppERK decay (though not to basal) between stimuli.…”

Temporal pattern and synergy influence activity of ERK signaling pathways during L-LTP induction

“…L-LTP simulations using 1 µM amplitude calcium pulses produce similar ppERK traces for ITIs between 3 and 40 sec (Figure 7A). Multiple 1 sec pulses of 1 µM calcium are similar to a single 5 sec pulse, due to the slow decay of pCaMKII; thus, calcium is above the threshold for CaMKII ultrasensitivity and ppERK is sustained for a long duration, consistent with experimental data showing that CaMKII above threshold is enough to induce sustain L-LTP (Shibata et al, 2021). Only with a 300 sec ITI does pCaMKII and ppERK decay (though not to basal) between stimuli.…”

Spatiotemporal Regulation of Transcript Isoform Expression in the Hippocampus

“…In the former, the terminal exon is different among isoforms, resulting in completely distinct 3′UTRs. For example, cell division cycle 42 ( Cdc42 ) is a Rho-family GTPase that is required for plasticity at CA1 spines (Murakoshi et al, 2011 ; Kim et al, 2014 ; Shibata et al, 2021 ) and has two splice variants with alternate last exons resulting in different C-terminal protein sequences and 3′UTRs ( Figure 2B ; Munemitsu et al, 1990 ; Shinjo et al, 1990 ; Marks and Kwiatkowski, 1996 ; Olenik et al, 1997 ). The proximal last exon is known as exon 6 or exon 6B, and is spliced into the brain-exclusive variant CDC42-palm (due to its palmitoylation modification, also known as CDC42-v2, CDC42-E6, CDC42b, and bCDC42, where b stands for brain; Marks and Kwiatkowski, 1996 ).…”