Boosting L-type Ca²⁺channel activity in tuberous sclerosis mitigates excess glutamate receptors

Abstract

Tuberous sclerosis complex (TS) is a dominant, multisystem disorder with devastating neurological symptoms. Approximately 85% of TS patients suffer from epilepsy over their lifespan and roughly 25-50% of those patients develop Autism Spectrum Disorder (1, 2). Current seizure therapies are effective in some, but not all, and often have significant risk factors associated with their use (1, 3). Thus, there is a critical need for new medication development or drug repositioning. Herein, we leveraged proteomic signatures of epilepsy and ASD, often comorbid in TS, to utilize an in silco approach to identify new drug therapies for TS-related seizures. We have discovered that activation of L-type voltage dependent calcium channels (L-VDCC) by Bay-K8644 (BayK) in a preclinical mouse model of TS curtails seizure frequency. Remarkably, at the molecular level, excess expression of ionotropic, AMPA-subtype glutamate (GluA) receptors is rescued by the administration of BayK. As added proof of BayK working through L-VDCC to regulate GluA levels, we found that increasing expression of alpha2delta2 (α2δ2), an auxiliary calcium channel subunit that boosts L-VDCC surface expression, similarly lowers the surface expression of dendritic GluA in TS. These BayK-induced molecular and functional alterations may underlie the longer lifespan of TS mice treated with BayK.Significance StatementCausal mechanisms of Tuberous Sclerosis (TS)-associated neurological disorders are under-characterized and treatment options are lacking. Using a computational approach of mTOR/DJ-1 target mRNAs to predict new medications, we report that boosting L-type voltage-dependent Ca2+ channel (L-VDCC) activity in a preclinical TS mouse model that exhibits a deficit in dendritic L-VDCC activity ameliorates key molecular and electrophysiological pathologies that are predicted to underlie seizures. Additionally, boosting L-VDCC activity extends lifespan. Restoring the mTOR/DJ-1 pathway upstream of L-VDCC, therefore, may serve as a new therapeutic avenue to mitigate seizures and mortality in TS.

AsHC 360 Exposure Influence on Epileptiform Discharges in Hippocampus of Infantile Male Rats In Vitro

“…For example, (S)-(-)-Bay-K-8644, a dihydropyrimidine derivative, enhances the opening probability of a specific subtype of L-type Ca 2+ channel. This action promotes voltage-dependent calcium influx and corrects the expression of glutamate receptor [41,42]. Although no direct study has investigated how AsHCs interact with EDs, analogous research suggests that (1) low concentrations of sodium arsenite (0-1 µM) can increase AMPAR expression, whereas higher concentrations (>1 µM) inhibit the expression of specific subunit glutamate receptor 1 [30]; (2) substantial amount of AsHC 360 (45-150 µg As L −1 ) can disturb nerve cell membrane integrity, subsequently affecting NMDAR and AMPAR activity [15].…”