Gating effects of a Cav2.3 calcium channel variant linked to developmental and epileptic encephalopathy

Developmental and epileptic encephalopathies (DEEs) are a group of neurological disorders that primarily affect young children and are characterized by severe seizures. DEEs are challenging to manage, with some patients experiencing severe side effects or not responding to frontline therapies. The CACNA1E gene, which encodes the voltage-gated calcium channel Cav2.3 (R-type), has recently been associated with DEEs. More than fifteen different variants in CACNA1E have been identified in patients with DEEs; however, the mechanisms by which these variants affect channel function and, thus, their relationship to DEEs, remain largely unknown. Previous research has begun to characterize the functional effects of R-type channel variants on channel biophysics, but only a handful of them have been studied functionally to date. Here, we transiently expressed Cav2.3 channels in a tsA-201 cell expression system and used whole-cell patch-clamp to examine the biophysics of one specific disease-associated R-type channel variant in which leucine 228 is substituted with a proline (L228P). Compared to wild-type, the L228P mutant did not present altered peak current density, inactivation kinetics, or recovery from inactivation, but showed a significant shift towards hyperpolarized voltages in both voltage-dependent activation and steady-state inactivation. This resulted in a broader window current shifted towards more hyperpolarized potentials, which predicts increased channel availability and activity at subthreshold voltages relative to wild-type channels. Our results contribute to the ongoing characterization of R-type variants, with the long-term goal of informing mechanism-specific therapies for DEEs.