Arc is a flexible modular protein capable of reversible self-oligomerization

Abstract

The immediate early gene product Arc (activity-regulated cytoskeleton-associated protein) is posited as a master regulator of long-term synaptic plasticity and memory. However, the physicochemical and structural properties of Arc have not been elucidated. In the present study, we expressed and purified recombinant human Arc (hArc) and performed the first biochemical and biophysical analysis of hArc's structure and stability. Limited proteolysis assays and MS analysis indicate that hArc has two major domains on either side of a central more disordered linker region, consistent with in silico structure predictions. hArc's secondary structure was estimated using CD, and stability was analysed by CD-monitored thermal denaturation and differential scanning fluorimetry (DSF). Oligomerization states under different conditions were studied by dynamic light scattering (DLS) and visualized by AFM and EM. Biophysical analyses show that hArc is a modular protein with defined secondary structure and loose tertiary structure. hArc appears to be pyramid-shaped as a monomer and is capable of reversible self-association, forming large soluble oligomers. The N-terminal domain of hArc is highly basic, which may promote interaction with cytoskeletal structures or other polyanionic surfaces, whereas the C-terminal domain is acidic and stabilized by ionic conditions that promote oligomerization. Upon binding of presenilin-1 (PS1) peptide, hArc undergoes a large structural change. A non-synonymous genetic variant of hArc (V231G) showed properties similar to the wild-type (WT) protein. We conclude that hArc is a flexible multi-domain protein that exists in monomeric and oligomeric forms, compatible with a diverse, hub-like role in plasticity-related processes.

Plasticity of Spine Structure: Local Signaling, Translation and Cytoskeletal Reorganization

“…Arc and viral Gag share key functional features such as membrane binding (Barylko et al, 2018), self-oligomerization of capsid-like protein (Myrum et al, 2015; Ashley et al, 2018; Pastuzyn et al, 2018), RNA-binding and EV-mediated exosomal releases (Ashley et al, 2018; Pastuzyn et al, 2018; Shepherd, 2018). It is still elusive whether other proteins and mRNAs can be also transferred between neurons through similar mechanisms.…”

Common variants in the ARC gene are not associated with cognitive abilities

“…Recent studies show that the Arc protein self‐oligomerizes, contains two biochemically distinct domains that flank a disordered region, and originated from the Ty3/Gypsy retrotransposon family (Myrum et al. ; Zhang et al. ).…”

“…Synthesis of Arc is required for longterm potentiation (LTP) and long-term depression (LTD), the major cellular mechanisms for synaptic strengthening and weakening, respectively Plath et al 2006;Rial Verde et al 2006;Shepherd et al 2006;Messaoudi et al 2007;Panja et al 2014). Recent studies show that the Arc protein self-oligomerizes, contains two biochemically distinct domains that flank a disordered region, and originated from the Ty3/Gypsy retrotransposon family (Myrum et al 2015;Zhang et al 2015).…”

Molecular determinants of Arc oligomerization and formation of virus-like capsids

“…Arc was identified in a computational search for domesticated retrotransposons harboring Gag-like protein domains (Campillos et al, 2006). Biochemical studies showed that mammalian Arc has a positively charged N-terminal domain (NTD) and a negatively charged Cterminal domain (CTD), separated by a flexible linker (Myrum et al, 2015). Crystal structure analysis of the isolated CTD revealed two lobes, both with striking 3D homology to the capsid (CA) domain of HIV Gag (Zhang et al, 2015).…”