Arpin Regulates Migration Persistence by Interacting with Both Tankyrases and the Arp2/3 Complex

Cell migration is a complex process involving dynamic rearrangements of the actin cytoskeleton. Established knowledge shows that Arp2/3-dependent branched actin networks are central to leading edge protrusion during migration. However, the mechanisms controlling migration persistence remain unclear. Prior research has shown that Arpin inhibits Arp2/3 activity, but the regulatory pathways governing Arpin function are not fully understood. This gap motivated the search for Arpin's interacting partners. No prior work had resolved how Arpin's interactions with other proteins influence migration persistence. Existing studies have identified Arpin's role in actin regulation, but the functional consequences of its protein interactions are less explored. This paper's contribution lies in uncovering Arpin's dual interactions with TNKS and Arp2/3. The study provides insights into how Arpin's binding to multiple proteins may regulate migration dynamics. The findings suggest that Arpin's regulatory role is more nuanced than previously assumed.

The aim of this study was to identify and characterize the interacting partners of Arpin to better understand its regulatory mechanisms. The specific problem addressed is how Arpin controls migration persistence through protein interactions. The motivation stems from the need to clarify the functional consequences of Arpin's interactions with TNKS and Arp2/3. The researchers propose that Arpin's interactions with these proteins are critical for its regulatory role. The study sought to determine whether these interactions are functionally distinct or overlapping. The goal was to test whether disrupting these interactions affects Arpin's activity. The researchers hypothesized that Arpin's binding to TNKS and Arp2/3 may involve separate pathways. The study aimed to provide a mechanistic framework for Arpin's role in migration regulation.

The researchers used a yeast two-hybrid screening to identify Arpin's interacting partners. They employed coimmunoprecipitation with full-length Arpin as bait to confirm interactions. The study mapped Arpin's C-terminal-binding site on its acidic tail. The team investigated how Arpin interacts with ankyrin repeats of TNKS. They tested whether Arpin could dissolve TNKS's liquid-liquid phase separation. Point mutations were introduced in the Arpin tail to uncouple interactions with TNKS and Arp2/3. The researchers used random plasmid integration to rescue Arpin knockout cells. Compensating knock-ins at the ARPIN locus were also attempted to assess Arpin activity.

Arpin was found to interact with both Tankyrase 1 and 2 (TNKS) via ankyrin repeats. The interaction occurs through a C-terminal-binding site on Arpin's acidic tail. This site overlaps with Arp2/3's binding region on Arpin. Arpin was shown to dissolve TNKS's liquid-liquid phase separation upon overexpression. Point mutations in Arpin's tail were introduced to disrupt interactions with TNKS and Arp2/3. Mutations impairing interactions with either protein were insufficient to abolish Arpin activity. Only mutations affecting both interactions rendered Arpin inactive. These findings suggest two independent pathways for Arpin's regulation of migration persistence.

The authors propose that Arpin regulates migration persistence through two distinct pathways. The study suggests that Arpin's interactions with TNKS and Arp2/3 are functionally independent. The findings indicate that Arpin's acidic tail is critical for both interactions. The researchers conclude that disrupting either interaction alone does not fully inactivate Arpin. The study supports the idea that Arpin's regulatory role involves multiple binding events. The results suggest that Arpin's activity is context-dependent on its binding partners. The authors propose that Arpin's dual interactions may allow for fine-tuned control of migration. The study provides a framework for understanding Arpin's role in actin regulation.