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CDKL5 Publication Breakdown: specific inhibitor of CDKL5

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In this blog series, IFCR’s Science Director, Heidi Grabenstatter, breaks down CDKL5 publications in easy-to-understand language.

Publication: Castano A, Silvestre M et al., Discovery and characterization of a specific inhibitor of serine-threonine kinase cyclin-dependent kinase-like 5 (CDKL5) demonstrates role in hippocampal CA1 physiology. eLife 2023;12:e88206. DOI: https://doi.org/10.7554/eLife.88206 

What was the researcher looking to learn in this research? While CDKL5 is a key mediator of synaptic and network development and physiology, the precise role of this kinase as explored through genetic manipulations in rodent models, remains unclear. This knowledge gap prevents a full understanding of the role of CDKL5 across development and has implications for determining and interpreting when protein and gene replacement strategies may be most efficacious. As CDKL5 kinase function is central to disease pathology, the authors developed a specific CDKL5 kinase inhibitor aimed to address this gap.

It is unclear why long term potentiation (LTP) may be enhanced, but seizures are lacking in knockout CDKL5 rodent models. It has been suggested that rodent-specific compensations may be responsible for the mismatch. To address this and to better understand the role of acute CDKL5 kinase dysfunction at any developmental time point, the authors sought to develop a sensitive and specific inhibitor of CDKL5.

What did they learn? CAF-382, the lead candidate CDKL5 inhibitor that the group identified, inhibited EB2 phosphorylation in primary neuron cultures and hippocampal slices. In the same experiments, CAF-382 did not reduce GSK3 activity.

Several electrophysiological methods were used in hippocampal slice preparations to better understand CDKL5 in regulating excitatory synaptic transmission and determined that acute CDKL5 inhibition by CAF-382 on glutamatergic synaptic transmission is (1) primarily post-synaptic, (2) selectively reduces AMPA-type glutamate receptor-mediated responses, and (3) CDKL5 has a direct role in the post-synaptic mediation of LTP.

What does this mean for the landscape of CDKL5 research? The authors synthesized and characterized a specific, high-affinity inhibitor of CDKL5 that does not have detectable activity for GSK3β. This compound is very soluble in water, but blood-brain barrier penetration is low. In rat hippocampal brain slices, acute inhibition of CDKL5 selectively reduces the post-synaptic function of AMPA-type glutamate receptors in a dose-dependent manner. Acute inhibition of CDKL5 reduces hippocampal LTP. These studies provide new tools and insights into the role of CDKL5 as a newly appreciated key kinase necessary for synaptic plasticity. Comparisons to rodent knock-out studies suggest that compensatory changes have limited the understanding of the roles of CDKL5 in synaptic physiology, plasticity and human neuropathology.

How was IFCR connected to this research? CDKL5 research funded by our organization promotes interdisciplinary collaborations that further the field. In this publication, the collaboration between experts in the CDD field and outside experts was funded by NIH-NINDS (NS112770).