Abstract
The activity-regulated cytoskeletal-associated protein (Arc, also known as Arg3.1) is an immediate early gene product induced by activity/experience and required for multiple modes of synaptic plasticity. Both long-term potentiation (LTP) and long-term depression (LTD) are impaired upon Arc deletion, as well as the ability to form long-term spatial, taste and fear memories. The best-characterized cellular function of Arc is enhancement of the endocytic internalization of AMPA receptors (AMPARs) in dendritic spines. Solution of the crystal structure of a C-terminal segment of Arc revealed a striking similarity to the capsid domain of HIV Gag. It was subsequently shown that Arc assembles into viral capsid-like structures that enclose Arc mRNA, are released into the extracellular space, and are internalized by neighboring cells. Thus, Arc is unique in participating in plasma membrane budding both into and out of the cell. In this report we study the interaction of Arc with membranes using giant unilamellar vesicles (GUVs). Using the fluorescent lipid probe LAURDAN, we find that Arc promotes the formation of smaller vesicles that penetrate into the GUV interior. Our results suggest that Arc induces negative membrane curvature and may therefore facilitate the formation of mRNA-containing extracellular vesicles from the plasma membrane.
Highlights
The activity-regulated cytoskeleton-associated (Arc) protein is a major regulator of synaptic plasticity and long-term memory consolidation (Bramham et al, 2010; Zhang and Bramham, 2020)
We previously reported that recombinant murine Arc elutes from gel filtration columns in several distinct but overlapping peaks, consistent with the presence of at least three low-order oligomeric species and one high-order species (Byers et al, 2015)
We found that the A260/280 of Arc decreased from ∼1.0 to ∼0.57 if bacterial lysates were precipitated with 35% ammonium sulfate (AS) prior to Arc purification (Figure 1A)
Summary
The activity-regulated cytoskeleton-associated (Arc) protein is a major regulator of synaptic plasticity and long-term memory consolidation (Bramham et al, 2010; Zhang and Bramham, 2020). Changes in Arc expression influence the strength of individual synapses, during both longterm potentiation (LTP) (Rodriguez et al, 2005; Yilmaz-Rastoder et al, 2011) and long-term depression (LTD) (Park et al, 2008; Waung et al, 2008; Wall and Correa, 2018). Arc was fluorescently labeled by reacting the protein with Alexa Fluor 594/647 NHS Ester (A20004, ThermoFisher, Waltham, MA, United States) overnight at 4°C. Arc-Alexa 594/647 was added to the GUV-containing imaging wells to a final protein concentration of 2–9 μM.
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