The E1015K Variant in the Synprint Region of the CaV2.1 Channel Alters Channel Function and Is Associated with Different Migraine Phenotypes

Mutations in the CACNA1A gene, which encodes the pore- forming ?1A subunit of the CaV2.1 voltage-gated calcium chan- nel, cause a number of human neurologic diseases including familial hemiplegic migraine. We have analyzed the functional impact of the E1015K amino acid substitution located in the "synprint" domain of the ?1A subunit. This variant was identi- fied in two families with hemiplegic migraine and in one patient with migraine with aura. The wild type (WT) and the E1015K forms of the GFP-tagged ?1A subunit were expressed in cul- tured hippocampal neurons and HEK cells to understand the role of the variant in the transport activity and physiology of CaV2.1. The E1015K variant does not alter CaV2.1 protein expression, and its transport to the cell surface and synaptic terminals is similar to that observed for WT channels. Electro- physiological data demonstrated that E1015K channels have increased current density and significantly altered inactivation properties compared with WT. Furthermore, the SNARE pro- teins syntaxin 1A and SNAP-25 were unable to modulate volt- age-dependent inactivation of E1015K channels. Overall, our findings describe a genetic variant in the synprint site of the CaV2.1 channel which is characterized by a gain-of-function and associated with both hemiplegic migraine and migraine with aura in patients.