Epilepsy-linked kinase CDKL5 phosphorylates voltage-gated calcium channel Cav2.3, altering inactivation kinetics and neuronal excitability

Developmental and epileptic encephalopathies (DEEs) are a group of rare childhood disorders characterized by severe epilepsy and related cognitive deficits. Numerous DEE genes have been discovered thanks to advances in genomic diagnosis, yet putative molecular links between these disorders are not known. CDKL5 deficiency disorder (CDD, DEE2) is one of the most common forms of genetic epilepsy; it is caused by loss-of-function mutations in the brain-enriched kinase CDKL5. To elucidate CDKL5 function, we looked for CDKL5 substrates using a SILAC based phosphoproteomic screen. We identified the voltage-gated Ca2+ channel Cav2.3 (encoded by CACNA1E) as a novel physiological target of CDKL5 in mice and humans. Recombinant channel electrophysiology and interdisciplinary characterization of Cav2.3 phosphomutant mice revealed that the loss of Cav2.3 phosphorylation leads to channel gain-of-function via slower channel inactivation and enhanced acetylcholine-induced stimulation, resulting in increased neuronal excitability. These changes in Cav2.3 closely resemble those described for gain-of-function point-mutations in CACNA1E that cause DEE69, a disorder sharing clinical features with CDD. Our results show that these two single-gene disorders are mechanistically related. We suggest that CDD is partly a channelopathy with Cav2.3 gain-of-function, thus Cav2.3 inhibition could be therapeutic in these DEEs. ### Competing Interest Statement The authors have declared no competing interest.