T-type CaV3.2 calcium channels are widely expressed in various types of neurons and dysfunction of CaV3.2 channels has been strongly implicated in human childhood absence epilepsy (CAE). However, the role of these calcium channels in neurons remains unknown. More surprisingly, ~50% CAE patients did not respond to ethosuximide, a T-type Ca2+ channel antagonist and first-line drug used to treat CAE, and most of the nonresponsive patients carry gain-of-function Cav3.2 mutations. In this project, we plan to investigate the functional role of CaV3.2 channels in neuronal cells and the pathogenesis of ~20 CAE-linked human CaV3.2 channel mutations. In the preliminary investigation, we manipulated the activity of CaV3.2 channels genetically and pharmacologically, and monitored the effects with electrophysiological, two-photon imaging, electron microscopic and behavioral analyses. Our preliminary results consistently show that unlike other calcium channels, CaV3.2 channels function primarily to regulate NMDA-R-mediated transmission at synapses. Therefore, we hypothesize that CaV3.2 channels regulate synaptic NMDA transmission and that CAE- linked CaV3.2 channel mutations enhance susceptibility to absence seizures by potentiating glutamatergic transmission. Specifically, we will examine whether the activity of CaV3.2 channels enhances NMDA and AMPA responses in multiple different types of rat neurons in vitro and in vivo (Aim 1a). Moreover, we plan to study whether CaV3.2 channel activity-coupled synaptic calcium influx enhances NMDA responses that lead to the secondary potentiation of AMPA responses (Aim 1b). These results will define that the primary physiological function of neuronal CaV3.2 channels is to regulate glutamatergic synaptic transmission. In addition, we will examine how each of ~20 CAE- linked human CaV3.2 mutations may affect synaptic glutamatergic transmission (Aim 2a). Finally, we plan to investigate whether each of ~20 CAE-linked human CaV3.2 mutations may enhance the susceptibility to 2-4 Hz spike-and-wave discharges and absence-like seizures and if the seizures can be suppressed by glutamate receptor antagonists (Aim 2b). These results will shed new light on the mechanism and suggest new intervention for human CaV3.2 mutation-associated CAE.

Public Health Relevance

T-type CaV3.2 calcium channels are widely expressed in various types of neurons and strongly implicated in human childhood absence epilepsy (CAE), yet the role of neuronal CaV3.2 channels in physiological and pathological conditions remains unclear. This project aims to understand the physiological role of CaV3.2 channels in neuronal cells and neuropathy of CAE-linked human CaV3.2 channel mutations.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS091452-05
Application #
9608074
Study Section
Clinical Neuroplasticity and Neurotransmitters Study Section (CNNT)
Program Officer
Whittemore, Vicky R
Project Start
2015-02-01
Project End
2019-12-31
Budget Start
2019-01-01
Budget End
2019-12-31
Support Year
5
Fiscal Year
2019
Total Cost
Indirect Cost
Name
University of Virginia
Department
Pharmacology
Type
Schools of Medicine
DUNS #
065391526
City
Charlottesville
State
VA
Country
United States
Zip Code
22904
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