Arg interacts with cortactin to promote adhesion-dependent cell edge protrusion

Cell edge protrusions are vital for cell migration and adhesion processes. While the role of Abl-related gene (Arg) kinases in these processes is known, their exact molecular interactions remain unclear. Prior research has shown that Arg kinases influence actin polymerization, but how they interface with the Arp2/3 complex is not fully understood. Cortactin, an Arp2/3 complex regulator, is known to influence actin dynamics during adhesion. However, the specific role of Arg in modulating cortactin remains unexplored. Fibroblast adhesion to fibronectin is a well-studied model for cell edge protrusion. Despite this, the mechanisms by which Arg and cortactin interact to regulate protrusion are still unknown. This gap motivated the current investigation into the Arg-cortactin relationship. The study aims to clarify how these proteins contribute to adhesion-dependent protrusion. Understanding this interaction could provide insights into cell migration and adhesion regulation.

This study aimed to determine how Arg and cortactin interact to regulate cell edge protrusion during adhesion. The specific problem addressed is the lack of clarity regarding Arg's role in actin polymerization and its interaction with cortactin. By focusing on fibroblast adhesion to fibronectin, the researchers sought to identify the molecular mechanisms involved. The motivation stems from the need to understand how Arg and cortactin coordinate to influence protrusion. The study also aimed to test whether Arg and cortactin function redundantly in this process. By examining Arg-deficient and cortactin knockdown cells, the researchers could assess their individual and combined contributions. The work also aimed to determine the nature of the Arg-cortactin interaction. This investigation could help clarify the signaling pathways involved in cell edge dynamics.

The researchers used fibroblast cell lines with Arg deficiency and cortactin knockdown to assess protrusion defects. They reexpressed Arg and cortactin to determine if these defects could be restored. Protein interactions were analyzed using binding assays and phosphorylation studies. The Arg C terminus was examined for Pro-rich motifs that could bind cortactin. Cortactin's Src homology 3 domain was tested for its ability to interact with Arg. Phosphorylation events were tracked to identify additional binding sites for Arg's SH2 domain. Mutant proteins were generated to test whether specific residues were necessary for protrusion. The role of the Nck adapter was assessed to determine its contribution to the Arg-cortactin interaction. These methods allowed the researchers to dissect the molecular mechanisms of Arg and cortactin in protrusion.

Arg-deficient and cortactin knockdown fibroblasts showed similar defects in adhesion-dependent protrusion. Reexpression of Arg and cortactin restored protrusion in these cells. Arg interacts with cortactin through binding and catalytic events. The cortactin SH3 domain binds to a Pro-rich motif in Arg's C terminus. Arg phosphorylates cortactin, creating a binding site for Arg's SH2 domain. Mutations in residues involved in Arg-cortactin interactions abolished protrusion support. The Nck adapter is required for this process, as it binds phosphocortactin. These findings suggest that Arg, cortactin, and Nck1 work together to promote protrusion.

The study demonstrates that interactions between Arg, cortactin, and Nck1 are critical for adhesion-dependent cell edge protrusion. Arg and cortactin function together to regulate actin dynamics during fibroblast adhesion. The Pro-rich motif in Arg and the SH3 domain in cortactin mediate their interaction. Arg's phosphorylation of cortactin creates an additional binding site for Arg's SH2 domain. Mutations in these interaction sites disrupt protrusion formation. The Nck adapter is also required for this process. These findings suggest that Arg, cortactin, and Nck1 form a functional complex during protrusion. This work provides new insights into the molecular mechanisms of cell edge protrusion.