Ins and outs of T-channel structure function

Area of Science:

• Neuroscience
• Molecular Biology
• Biophysics

Background:

• T-channels are crucial for neuronal excitability and calcium signaling.
• Understanding T-channel structure is key to deciphering their function in health and disease.

Purpose of the Study:

• To review the structural and functional aspects of T-channels, focusing on Cav3.2.
• To elucidate the role of specific structural elements in T-channel gating and regulation.
• To explore the implications of T-channel dysfunction in epilepsy.

Main Methods:

• Structural analysis of T-channel components, including extracellular and intracellular regions.
• Investigation of a high-affinity metal-binding site and its role in channel function.
• Identification and characterization of an intracellular gating brake mechanism.
• Examination of T-channel mutations in cultured hippocampal neurons to study epilepsy.

Main Results:

• The high-affinity metal-binding site was localized to repeat I of Cav3.2, with histidine at position 191 playing a key regulatory role.
• The intracellular loop connecting repeats I and II influences Cav3.2 gating and surface expression.
• A conserved intracellular gating brake, predicted to form a helix-loop-helix structure, stabilizes the closed state of T-channels.
• Depolarization disrupts the gating brake, leading to channel opening and calcium influx.
• Mutations associated with idiopathic generalized epilepsy alter T-currents and activate transcription factors, increasing seizure susceptibility.

Conclusions:

• T-channel structure, particularly the metal-binding site and gating brake, is critical for channel function and regulation.
• T-channels play significant roles in neuronal excitability, calcium homeostasis, and cellular physiology.
• T-channel dysfunction contributes to the pathophysiology of epilepsy, offering potential therapeutic targets.