Biology subjects

Coultrap, S. J.

Publications and source records attributed to Coultrap, S. J..

4 recordsLinked to original sources

bioRxiv2026

CaMKII T286 autophosphorylation is not propagated at basal Ca2+ levels and is required only for the induction phase of LTP

The Ca2+/calmodulin-dependent protein kinase II (CaMKII) and its autophosphorylation at T286 (P-T286) mediates long-term potentiation (LTP) of synaptic strength. CaMKII forms stable 12-meric holoenzymes, but exchange of its subunits is proposed to propagate the P-T286 state beyond dephosphorylation or degradation of individual subunits. However, a recent study questioned subunit exchange and instead proposed P-T286 propagation by trans-holoenzyme phosphorylation. We show here that both subunit exchange and trans-holoenzyme P-T286 can occur (although cis-holoenzyme P-T286 is much preferred), but that neither mechanism propagates P-T286 at basal cellular Ca2+ levels (50-100 nM) in absence of further Ca2+-stimuli. Functionally, we show that after theta-burst stimulation (TBS), P-T286 is required only during the first minutes of LTP induction that prime for subsequent LTP expression, but neither for LTP expression itself nor for LTP maintenance. These results indicate that P-T286 of CaMKII does not self-perpetuate and does not mediate storage but computation of synaptic information.

neuroscience↗

bioRxiv2025

The CaMKII D135N mutation blocks kinase activity and reduces GluN2B binding

Three recent studies claimed that induction of long-term potentiation (LTP) of synaptic strength requires structural rather than enzymatic functions of the Ca2+/Calmodulin(CaM)-dependent protein kinase II (CaMKII). One study utilized the CaMKII D135N mutation, which was claimed to abolish enzymatic activity without affecting the structural function, i.e. binding to GluN2B. We found here that the D135N mutant indeed abolished enzymatic kinase activity and autophosphorylation at T286 (pT286). However, D135N mutation additionally reduced binding to GluN2B and prevented persistence of co-condensation with GluN2B. Similar as with the T286A mutant, GluN2B binding of the D135N mutant could be partially rescued by AS283, an inhibitor that directly enhances GluN2B binding. This partial effect on GluN2B binding has to be taken into account when using D135N to distinguish between enzymatic versus structural functions of CaMKII. Nonetheless, as discussed here, the D135N mutant indeed supports a structural rather than enzymatic CaMKII function in LTP induction.

neuroscience↗

bioRxiv2025

CaMKII monomers are sufficient for GluN2B binding, co-condensation, and synaptic potentiation

Cognitive functions require synaptic plasticity, specifically long-term potentiation (LTP). LTP is thought to require CaMKII binding to the NMDA-type glutamate receptor subunit GluN2B, but this poses a major conundrum: Truncated CaMKII monomers (without the hub domain that forms 12meric holoenzymes) fail to bind GluN2B, but still potentiate synapses when made constitutively active. We hypothesized that CaMKII monomer binding to GluN2B has just eluded detection. Instead, even though full-length CaMKII monomers (with hub domain mutations) were found to indeed bind and even co-condensate with GluN2B, truncated monomers were not. Nonetheless, truncated monomers still potentiated synapses, even in neurons with GluN2B mutations that ablate CaMKII binding. However, potentiation occurred only with monomers that were made Ca2+-independent by artificial phosphatase-resistant thio-autophosphorylation, not by regular autophosphorylation of T286. These findings support that CaMKII binding to GluN2B is required during physiological LTP induction because it generates the phosphatase-resistant autonomous activity that mediates LTP expression.

neuroscience↗

bioRxiv2021

Conserved and divergent features of neuronal CaMKII holoenzyme structure, function, and high-order assembly

Neuronal CaMKII holoenzymes (- and {beta}-isoforms) enable molecular signal computation underlying learning and memory, but also mediate excitotoxic neuronal death. Here, we provide a comparative analysis of these signaling devices, using single particle EM in combination with biochemical and live-cell imaging studies. In the basal state, both isoforms assembled mainly as 12-mers (but also 14-mers, and even 16-mers for the {beta}-isoform). CaMKII and {beta}-isoforms adopted an ensemble of extended activatable states (with average radius of 12.6 versus 16.8 nm, respectively), characterized by multiple transient intra- and inter-holoenzyme interactions associated with distinct functional properties. The extended state of CaMKII{beta} allowed EM analysis to directly resolve intra-holoenzyme kinase-domain dimers that could enable the cooperative activation mechanism by calmodulin, which was found for both isoforms. Surprisingly, high-order CaMKII clustering mediated by inter-holoenzyme kinase-domain dimerization was reduced for the {beta} isoform for both basal and excitotoxicity-induced clusters, both in vitro and in neurons.

molecular biology↗