Analysis of Arc/Arg3.1 Oligomerization In Vitro and in Living Cells.

Area of Science:

• Neuroscience
• Molecular Biology
• Cell Biology

Background:

• Arc (Arg3.1) is an activity-dependent immediate early gene vital for synaptic plasticity, including long-term potentiation and depression.
• Arc's functions involve actin cytoskeleton remodeling, AMPA receptor endocytosis, and regulating AMPA receptor subunit transcription.
• Arc shares similarities with retroviral Gag proteins, forming virus-like particles for potential intercellular mRNA transport.

Purpose of the Study:

• To investigate the oligomeric state of Arc in vitro and in living cells.
• To determine the concentration-dependent self-association of Arc.
• To identify the structural determinants of Arc's self-association.

Main Methods:

• Mass photometry was employed to analyze Arc's oligomeric state in vitro.
• Fluorescence fluctuation spectroscopy was used to study Arc's oligomerization in the cytoplasm of living cells.
• Structural analysis focused on the N-terminal domain's role in self-association.

Main Results:

• In vitro, Arc predominantly forms monomers, dimers, and trimers at nanomolar concentrations.
• In living cells, Arc exists mainly as low-order oligomers (monomer to tetramer) across a wide concentration range (200 nM to 5 μM).
• An α-helical segment within Arc's N-terminal domain was identified as critical for its self-association.

Conclusions:

• Arc's self-association into low-order oligomers is a fundamental property influencing its diverse cellular functions.
• The oligomeric state of Arc is maintained across different cellular environments and concentrations.
• Understanding Arc's oligomerization provides insights into its roles in synaptic plasticity and intercellular communication.