A novel missense mutation in the CACNA1A gene that encodes the pore forming α₁ subunit of the Ca_V2.1 voltage-gated calcium channel was identified in a patient with trigeminal neuralgia. This mutation leads to a substitution of proline 2455 by histidine (P2455H) in the distal C-terminus region of the channel. Due to the well characterized role of this channel in neurotransmitter release, our aim was to characterize the biophysical properties of the P2455H variant in heterologously expressed Ca_V2.1 channels. Whole-cell patch clamp recordings of wild type and mutant Ca_V2.1 channels expressed in tsA-201 cells reveal that the mutation mediates a depolarizing shift in the voltage-dependence of activation and inactivation. Moreover, the P2455H mutant strongly reduced calcium-dependent inactivation of the channel that is consistent with an overall gain of function. Hence, the P2455H Ca_V2.1 missense mutation alters the gating properties of the channel, suggesting that associated changes in Ca_V2.1-dependent synaptic communication in the trigeminal system may contribute to the development of trigeminal neuralgia.

De novo variants in CACNA1E, the gene encoding the Cav2.3 voltage-gated calcium channel, are often associated with severe neurodevelopmental disorders, including developmental and epileptic encephalopathy. All reported variants up to date have exhibited gain-of-function effects on their biophysical properties. Here, we functionally characterize three pathogenic CACNA1E variants: H151L, M163T, and R1182C, using electrophysiology and structural modeling. M163T and R1182C exhibit depolarizing shifts in the voltage-dependence of activation, whereas R1182C also shows a reduced peak current density. H151L selectively slows recovery from inactivation. Our findings provide the first mechanistic evidence linking loss-of-function Cav2.3 pathogenic variants to variable neurological phenotypes, expanding the clinical spectrum of CACNA1E channelopathies.