Experimental and computational evidence that Calpain-10 binds to the carboxy terminus of Na V 1.2 and Na V 1.6.

Voltage-gated sodium channels (NaV ) are pivotal proteins responsible for initiating and transmitting action potentials. Emerging evidence suggests that proteolytic cleavage of sodium channels by calpains is pivotal in diverse physiological scenarios, including ischemia, brain injury, and neuropathic pain associated with diabetes. Despite this significance, the precise mechanism by which calpains recognize sodium channels, especially given the multiple calpain isoforms expressed in neurons, remains elusive. In this work, we show the interaction of Calpain-10 with NaV 's C-terminus through a yeast 2-hybrid assay screening of a mouse brain cDNA library and in vitro by GST-pulldown. Later, we also obtained a structural and dynamic hypothesis of this interaction by modeling, docking, and molecular dynamics simulation. These results indicate that Calpain-10 interacts differentially with the C-terminus of NaV 1.2 and NaV 1.6. Calpain-10 interacts with NaV 1.2 through domains III and T in a stable manner. In contrast, its interaction with NaV 1.6 involves domains II and III, which could promote proteolysis through the Cys-catalytic site and C2 motifs.