Synapsin II Directly Suppresses Epileptic Seizures In Vivo

Area of Science:

• Neuroscience
• Molecular Biology
• Epilepsy Research

Background:

• Synapsins are key phosphoproteins regulating synaptic vesicle dynamics.
• Synapsin II (SynII) deficiency is linked to epilepsy, as demonstrated in SynII knockout (KO) mice exhibiting generalized seizures.
• Understanding SynII's direct role in epilepsy requires differentiating its effects from secondary adaptations.

Purpose of the Study:

• To investigate the direct impact of Synapsin II (SynII) on suppressing epileptic seizures and synaptic hyperexcitability.
• To elucidate the molecular mechanisms underlying SynII's anticonvulsant effects, including the role of protein kinase A (PKA) phosphorylation.

Main Methods:

• Adeno-associated virus (AAV)-mediated reintroduction of SynII into SynII KO mouse models.
• Electrophysiological recordings in hippocampal slices to assess synaptic activity and epileptiform discharges.
• Pharmacological challenge with 4-aminopyridine (4-AP) to induce seizures.
• In vivo assessment of behavioral seizures.
• Utilizing a phospho-incompetent SynII mutant to probe the role of PKA phosphorylation.

Main Results:

• SynII reintroduction significantly diminished enhanced synaptic activity in SynII KO hippocampal slices.
• SynII reintroduction fully rescued 4-aminopyridine-induced epileptiform activity in SynII KO slices.
• SynII reintroduction normalized behavioral seizures in young SynII KO animals.
• A phospho-incompetent SynII mutant partially suppressed seizure activity, indicating PKA phosphorylation contributes to SynII's anticonvulsant function.

Conclusions:

• Synapsin II directly suppresses seizure activity and synaptic hyperexcitability.
• Protein kinase A phosphorylation at a specific site is a contributing mechanism for SynII's anticonvulsant effects.
• These findings highlight SynII as a potential therapeutic target for epilepsy.