Cited by 126Neuroscience and Neuropharmacology ResearchMemory and Neural MechanismsProtein Kinase Regulation and GTPase Signaling

The DOI matches its Crossref record; 447 of the 450 references it cites were found in a registry or an index; 381 of the 692 sources its claims cite were checked for support.

Synaptic memory and CaMKII

Open access
Nicoll, Roger A., Schulman, Howard·2023·Physiological Reviews

Abstract

Ca 2+ /calmodulin-dependent protein kinase II (CaMKII) and long-term potentiation (LTP) were discovered within a decade of each other and have been inextricably intertwined ever since. However, like many marriages, it has had its up and downs. Based on the unique biochemical properties of CaMKII, it was proposed as a memory molecule before any physiological linkage was made to LTP. However, as reviewed here, the convincing linkage of CaMKII to synaptic physiology and behavior took many decades. New technologies were critical in this journey, including in vitro brain slices, mouse genetics, single-cell molecular genetics, pharmacological reagents, protein structure, and two-photon microscopy, as were new investigators attracted by the exciting challenge. This review tracks this journey and assesses the state of this marriage 40 years on. The collective literature impels us to propose a relatively simple model for synaptic memory involving the following steps that drive the process: 1) Ca 2+ entry through N-methyl-d-aspartate (NMDA) receptors activates CaMKII. 2) CaMKII undergoes autophosphorylation resulting in constitutive, Ca 2+ -independent activity and exposure of a binding site for the NMDA receptor subunit GluN2B. 3) Active CaMKII translocates to the postsynaptic density (PSD) and binds to the cytoplasmic C-tail of GluN2B. 4) The CaMKII-GluN2B complex initiates a structural rearrangement of the PSD that may involve liquid-liquid phase separation. 5) This rearrangement involves the PSD-95 scaffolding protein, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs), and their transmembrane AMPAR-regulatory protein (TARP) auxiliary subunits, resulting in an accumulation of AMPARs in the PSD that underlies synaptic potentiation. 6) The stability of the modified PSD is maintained by the stability of the CaMKII-GluN2B complex. 7) By a process of subunit exchange or interholoenzyme phosphorylation CaMKII maintains synaptic potentiation in the face of CaMKII protein turnover. There are many other important proteins that participate in enlargement of the synaptic spine or modulation of the steps that drive and maintain the potentiation. In this review we critically discuss the data underlying each of the steps. As will become clear, some of these steps are more firmly grounded than others, and we provide suggestions as to how the evidence supporting these steps can be strengthened or, based on the new data, be replaced. Although the journey has been a long one, the prospect of having a detailed cellular and molecular understanding of learning and memory is at hand.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

This review argues that CaMKII is both necessary and sufficient for NMDAR-dependent LTP induction and also maintains synaptic strength/memory, with CaMKII-GluN2B binding and T286 autophosphorylation as central mechanisms. It synthesizes biochemical, electrophysiological, imaging, and genetic evidence and highlights unresolved questions about downstream targets and maintenance.

Key findings

  • CaMKII inhibition blocks LTP induction; constitutively active CaMKII enhances AMPAR EPSCs roughly two- to threefold, selectively over NMDAR EPSCs, and occludes LTP.
  • Blocking CaMKII after LTP with myr-CN27 reduces control AMPAR EPSCs by ~50% and fully reverses established LTP; CRISPR deletion of CaMKII reduces synaptic transmission to ~50% of control.
  • CaMKII binding to GluN2B is required: CaMKII I205K prevents binding and blocks LTP; CA CaMKII with I205K fails to enhance; replacing GluN2B with L1298A/R1300Q reduces AMPAR responses ~50%.
  • T286 autophosphorylation is central: T286A replacement blocks LTP, and autophosphorylation increases Ca2+/CaM affinity >1,000-fold (15 nM to 20 pM); CaMKII has low Ca2+ sensitivity (apparent Kd = 1.6 µM; Hill coefficient ~6) versus resting Ca2+ (20–50 nM).

Methods

  • Narrative review of published literature on NMDAR-dependent LTP and CaMKII; no new experimental data or systematic search/meta-analysis are reported.
  • Focuses primarily on CA3-to-CA1 hippocampal synapses and the first hour of LTP, integrating biochemical, electrophysiological, imaging, genetic, and computational studies.
  • Figures are modified from prior studies; the review discusses three models of LTP expression (receptor-centric, PSD-centric, vesicle-centric).

Limitations

  • Stated: the review is limited to NMDAR-dependent LTP, primarily the first hour, and does not cover all LTP forms.
  • Stated: critical downstream targets of CaMKII remain elusive; LLPS role is speculative; T286 phosphorylation requirement for maintenance is debated; role of CaMKIIβ and S1303 phosphorylation unresolved.
  • Evident: as a narrative review, it does not systematically assess study quality, publication bias, or effect sizes across the literature.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1152/physrev.00034.2022

Cites

447 of 447 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Verification

Claims the paper makes

381 of 692 cited sources checked · 209 supported · 11 flagged · accuracy not yet measured

Show all 344 claims

  • It may state two separate claims as one. 145
  • Probably not a substantial claim. 42
  • The quote only partly states this claim. 1
178 of 178
  • The authors state this as an assumption.

    During a brief Ca2+ spike there is only time for a fraction of a dodecamer to be occupied and activated by Ca2+/CaM.

    “A reasonable assumption is that during a brief Ca2+ spike there is only time for a fraction of a dodecamer to be occupied and activated by Ca2+/CaM.”
  • The authors state this as an assumption.

    With the near-saturating pairing protocol used to induce LTP, the majority of the subunits of a holoenzyme would be phosphorylated.

    “It is assumed that with the near-saturating pairing protocol used to induce LTP the majority of the subunits of a holoenzyme would be phosphorylated (see last Ca2+ pulse in FIGURE 3B2).”
  • The authors state this as an assumption.

    With the standard saturating induction protocol used for LTP, the kinase would be highly phosphorylated, perhaps only limited by the availability of CaM.

    “It is assumed that with the standard saturating induction protocol used for LTP the kinase would be highly phosphorylated, perhaps only limited by the availability of CaM.”
  • The authors state this as an assumption.

    Native CaMKII holoenzymes are composed of a mixture of α- and β-isoforms.

    “Assuming that native CaMKII holoenzymes are composed of a mixture of α- and β-isoforms”
  • The paper relies on this without support.

    Memories can last for the entire span of an animal’s life.

    “Although memories can last for the entire span of an animal’s life, most synaptic proteins generally have half-lives of 2–5 days (403, 404).”
  • The authors state this as an assumption.

    The assembly of CaMKII holoenzymes involves transient free dimer subunits.

    “Assuming that the assembly of CaMKII holoenzymes involves transient free dimer subunits, perhaps these inactive dimers could be a source for subunit exchange.”
  • The paper relies on this without support.

    For CaMKII to exert its effect it must be bound to GluN2B.

    “We know that for CaMKII to exert its effect it must be bound to GluN2B.”
7 of 7

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • CBP concentration is given as both 1.1 mM and 190 μM

    Minor

    The Figure 5 caption assigns two different concentrations to the CBP-containing microelectrodes in the same experimental group.

  • References 200 and 217 identify the same journal pages as different articles

    Minor

    The two entries have the same authors, journal, volume, pages, year, and PubMed identifier, but give different titles and DOIs.

2 of 2

Citations

Cites

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Show all 450 references

3 of the 450 references couldn’t be matched to a known paper.

Research works printed but not linked: 3

  1. Lomo T, 1966, Acta Physiol Scand, 68
  2. Hebb DO. Organization of Behavior . New York: Wiley, 1949.
  3. Mangels LA, 1990, Mol Pharmacol, 37, 820

Cited by

Sorted by citations

Items 101–126 of 126

Metadata

Authors
Nicoll, R. A., & Schulman, H.
Affiliations
  • University of California, San Francisco (US)
  • Stanford Medicine (US)
Corresponding author
  • Nicoll, Roger A.
  • Schulman, Howard
Venue
Physiological Reviews
Published
2023-10-01
Volume
103
Issue
4
Pages
2897-2945
ISSN
  • 0031-9333 (ISSN-L)
  • 1522-1210
OpenAlex
W4379791499
Cited by
126
References
450
Citations by year
2026: 34 · 2025: 55 · 2024: 33 · 2023: 4
FWCI
4.98
Type
journal article
Language
en
Open access
Licence
cc-by
Locations
  • Physiological Reviews (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • PubMed Central (submittedVersion, cc-by)
Funders
HHS | NIH | National Institute of Mental Health (NIH (R01MH117139))
Topics
  • Life Sciences › Neuroscience › Cellular and Molecular Neuroscience › Neuroscience and Neuropharmacology Research
  • Life Sciences › Neuroscience › Cognitive Neuroscience › Memory and Neural Mechanisms
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Protein Kinase Regulation and GTPase Signaling
Keywords
CaMKII, synaptic memory, long-term potentiation, NMDA receptor, GluN2B, autophosphorylation, postsynaptic density, liquid-liquid phase separation, PSD-95, synaptic potentiation, synaptic spines, memory reconsolidation
MeSH terms
Animals, Hippocampus, Learning, Memory, Long-Term Potentiation, Mice, Calcium-Calmodulin-Dependent Protein Kinase Type 2

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