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Published on: October 30, 2018
Aβ-induced synaptic impairments require CaMKII activity that is stimulated by indirect signaling events
Carolyn Nicole Brown1, Nicole L Rumian1,2, Jonathan E Tullis1
1Department of Pharmacology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA.
Abstract:
Aβ bears homology to the CaMKII regulatory domain, and peptides derived from this domain can bind and disrupt the CaMKII holoenzyme, suggesting that Aβ could have a similar effect. Notably, Aβ impairs the synaptic CaMKII accumulation that is mediated by GluN2B binding, which requires CaMKII assembly into holoenzymes. Furthermore, this Aβ-induced impairment is prevented by CaMKII inhibitors that should also inhibit the putative direct Aβ binding. However, our study did not find any evidence for direct effects of Aβ on CaMKII: Aβ did not directly disrupt CaMKII holoenzymes, GluN2B binding, T286 autophosphorylation, or kinase activity in vitro. Most importantly, in neurons, the Aβ-induced impairment of CaMKII synaptic accumulation was prevented by an ATP-competitive CaMKII inhibitor that would not interfere with the putative direct Aβ binding. Together, our results indicate that synaptic Aβ effects are not mediated by direct binding to CaMKII, but instead require CaMKII activation via indirect signaling events.
Insights
Amyloid-beta (Aβ) does not directly interact with Calcium/calmodulin-dependent protein kinase II (CaMKII). Instead, Aβ impairs synaptic function through indirect signaling pathways that activate CaMKII.
Area of Science:
- Neuroscience
- Molecular Biology
- Biochemistry
Background:
- Amyloid-beta (Aβ) shares structural similarities with the regulatory domain of Calcium/calmodulin-dependent protein kinase II (CaMKII).
- Previous research suggested Aβ might directly inhibit CaMKII holoenzyme function, impacting synaptic plasticity.
- Aβ is known to impair synaptic CaMKII accumulation, a process dependent on GluN2B binding and CaMKII holoenzyme assembly.
Purpose of the Study:
- To investigate whether Aβ directly binds to and affects CaMKII holoenzymes, GluN2B binding, autophosphorylation, or kinase activity.
- To elucidate the mechanism by which Aβ impairs synaptic CaMKII accumulation.
- To determine if Aβ's effects on synaptic CaMKII are mediated by direct interaction or indirect signaling.
Main Methods:
- In vitro assays to assess direct effects of Aβ on CaMKII holoenzymes, GluN2B binding, T286 autophosphorylation, and kinase activity.
- Neuronal cultures to examine the impact of Aβ on CaMKII synaptic accumulation.
- Utilized ATP-competitive CaMKII inhibitors to differentiate between direct and indirect Aβ effects.
Main Results:
- No direct disruption of CaMKII holoenzymes, GluN2B binding, T286 autophosphorylation, or kinase activity by Aβ in vitro.
- Aβ-induced impairment of synaptic CaMKII accumulation in neurons was observed.
- This impairment was preventable by an ATP-competitive CaMKII inhibitor, indicating an indirect mechanism not involving direct Aβ binding.
Conclusions:
- Synaptic Aβ effects are not mediated by direct binding to CaMKII.
- Aβ impairs synaptic CaMKII accumulation through indirect signaling events that lead to CaMKII activation.
- Understanding these indirect pathways is crucial for developing therapeutic strategies targeting Aβ-related synaptic dysfunction.
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