CDKL5

CDKL5 is a brain-enriched serine/threonine kinase that supports neuronal development, synaptic physiology, and network function^[1]. Mechanistically, CDKL5 phosphorylates microtubule-associated proteins MAP1S, EB2/MAPRE2, and ARHGEF2, linking CDKL5 activity to dendritic microtubule dynamics and cargo trafficking^[2]. In neuronal systems, CDKL5-dependent EB2 Ser222 phosphorylation provides a practical activity readout for substrate signaling and pathway compensation^[3]. In disease models, loss-of-function CDKL5 mutations cause CDKL5 deficiency disorder, a severe neurodevelopmental disorder with early-life epilepsy and motor, cognitive, visual, and autonomic disturbances^[4]. Postdevelopmental Cdkl5 deletion disrupts behavior, hippocampal circuit communication, and dendritic spine morphology, while late Cdkl5 restoration ameliorates behavioral impairments and aberrant NMDA receptor signaling in male mice^[5]. Compared with related isoforms, hCDKL5_1 is the predominant human brain transcript, whereas human and mouse CDKL5 transcripts show broader diversity through alternative promoter usage, first-exon usage, splicing, and distinct C-terminal regions^[6]. Compared with related kinases, CDKL2 and ICK can phosphorylate EB2 S222, and CDKL2 phosphorylates CDKL5 substrates in mouse brain, indicating partial kinase compensation rather than simple isoform equivalence^[3]. For experimental applications, selective CDKL5 inhibitors offer tools to test acute kinase function; these inhibitors reduce AMPA-receptor postsynaptic function and hippocampal LTP but show low blood-brain barrier penetration^[4].