Optical inactivation of synaptic AMPA receptors erases fear memory

Developers

Kiwamu Takemoto, Hiroko Iwanari, Takeharu Nagai, Takao Hamakubo, Takuya Takahashi, etc.

Description of the technology

The synaptic delivery of neurotransmitter receptors, such as GluA1 AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptors, mediates important processes in cognitive function, including memory acquisition and retention. Understanding the roles of these receptors has been hampered by the lack of a method to inactivate them in vivo with high spatiotemporal precision.

Authors developed a technique to inactivate synaptic GluA1 AMPA receptors using chromophore-assisted light inactivation (CALI). They raised a monoclonal antibody specific for the extracellular domain of GluA1 that induced effective CALI when conjugated with a photosensitizer (eosin). Mice that had been injected in the CA1 hippocampal region with the antibody conjugate underwent a fear memory task. Exposing the hippocampus to green light using an implanted cannula erased acquired fear memory in the animals by inactivation of synaptic GluA1.

GluA1 homomeric receptors are involved in long-term potentiation. The latter is the mechanism for the activity dependent strengthening of synapses that is thought to contribute to learning. GluA1 homomeric receptors are delivered into synapses at the early phase of LTP, and this delivery is required for long-term potentiation maintenance, presumably by providing Ca2+ through GluA1 homomeric receptors; besides, Ca2+ is critical for protein synthesis. In this study, GluA1 homomeric receptors was inactivated by in vivo chromophore-assisted light inactivation 1 h after conditioning. It erased contextual fear memory. This inactivation could also have disrupted Ca2+ influx at the early phase of memory encoding, and caused the continued erasure of fear memory.

This method gives the valuable tool for future to study and manipulate complex behavior processes, such as memory, learning, etc, which serve the basis of complicated and long-term transformations in living organism, for example diseases of ageing, associated with changes of memory processes.

Practical application

The optical technique for inactivating synaptic proteins will enable elucidation of their physiological roles in cognition. The used approach provides a useful tool for elucidating not only the roles of GluA1 AMPA receptors, but also other synaptic proteins in cognitive function in various brain areas as well as in individual spines.
The technology can be applicable for study and modelling of memory changes in physiological conditions and diseases, as well as in process of transformations in organism with the course of time, for example, during ageing.

Laboratories

• Yokohama City University Graduate School of Medicine, Department of Physiology, Yokohama (Japan)
• Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, Kawaguchi, Saitama (Japan)
• The University of Tokyo, Department of Quantitative Biology and Medicine, Research Center for Advanced Science and Technology (RCAST), Meguro-ku, Tokyo (Japan)
• Osaka University, The Institute of Scientific and Industrial Research, Ibaraki, Osaka (Japan)

Links

Publications

• Takemoto, K. et al. «Optical inactivation of synaptic AMPA receptors erases fear memory." 35 Nature Biotechnology, (2017): 38–47.
• Takemoto, K. et al. «SuperNova, a monomeric photosensitizing fluorescent protein for chromophore-assisted light inactivation." 3 Sci. Rep. (2013): 2629.
• Takahashi, N. et al. «Locally synchronized synaptic inputs." 335 Science, (2012): 353–356.