Lithium increases synaptic GluA2 in hippocampal neurons by elevating the δ-catenin protein

Area of Science:

• Neuroscience
• Molecular Biology
• Pharmacology

Background:

• Lithium (Li+) is a key treatment for bipolar disorder, but its precise mechanism of action remains unclear.
• Synaptic dysfunction is implicated in neurological disorders, highlighting the importance of understanding synaptic protein regulation.

Purpose of the Study:

• To investigate the effects of Li+ on the synaptic complex involving delta-catenin, GRIP, and AMPA receptors (AMPARs) in hippocampal neurons.
• To elucidate the molecular mechanism by which Li+ influences synaptic function and potentially impacts neurological disease treatment.

Main Methods:

• Utilized cultured hippocampal neurons and animal models to study the impact of Li+ on synaptic protein levels.
• Employed biochemical assays and electrophysiology to assess protein interactions, receptor surface expression, and synaptic activity (mEPSCs).

Main Results:

• Li+ elevated delta-catenin levels, which in turn increased GRIP and GluA2 (an AMPAR subunit) levels at synapses.
• The enhanced surface expression of GluA2 was dependent on its interaction with GRIP.
• Li+ increased the amplitude, but not frequency, of miniature excitatory postsynaptic currents (mEPSCs), indicating functional AMPAR stabilization.

Conclusions:

• Li+ stabilizes delta-catenin, leading to the elevation of a synaptic complex comprising delta-catenin, GRIP, and AMPARs in hippocampal neurons.
• This mechanism provides insight into how Li+ modulates brain synaptic function, potentially explaining its therapeutic effects in neurological conditions.