# TRAF2 and NCK interacting kinase: a novel regulator of integrin αIIbβ3 signaling in platelets

## TL;DR

This study shows that TNIK, a kinase, plays a key role in platelet function by regulating integrin signaling and could be a new target for preventing blood clots.

## Contribution

The study is the first to show TNIK's role in platelet function and its connection to integrin αIIbβ3 signaling.

## Key findings

- TNIK inhibition reduces platelet aggregation, granule secretion, and thrombus formation.
- TNIK links the actin cytoskeleton to integrin αIIbβ3 through interactions with focal adhesion proteins.
- TNIK is essential for platelet adhesion, spreading, and clot retraction via integrin activation.

## Abstract

TRAF2 and NCK interacting kinase (TNIK) is a serine/threonine kinase member of the germinal center kinase family. Previously, in other cell types, TNIK has been shown to interact with key cytoskeletal regulatory proteins, to regulate F-actin distribution, cell polarization, and neuronal cell arborization. Proteomic studies have demonstrated TNIK is present in platelets; however, no further studies have explored if TNIK plays a role in the regulation of platelet function.

We sought to investigate the distribution of TNIK in platelets and characterize a potential role for TNIK in platelet function.

The importance of platelet TNIK was explored using 2 structurally distinct TNIK inhibitors (KY-05009 and NCB-0846) in aggregometry, assays of granule secretion, calcium mobilization and thrombus formation, and using confocal microscopy and co-immunoprecipitation.

TNIK inhibition diminished platelet responses, and thrombus formation under arterial shear. Furthermore, TNIK regulated platelet adhesion and spreading on fibrinogen and impaired clot retraction due to reduced integrin αIIbβ3 activation. Co-immunoprecipitation studies demonstrated that TNIK bridges interactions between the actin cytoskeleton and integrin αIIbβ3 through direct associations with focal adhesion kinase, paxillin, kindlin-3, filamin A, Rap2a, gelsolin and actin.

In summary, we confirm TNIK is present in platelets and is important for platelet function, and thrombus formation. For the first time, we show that platelet TNIK is able to associate with key cytoskeletal regulators, linking its signaling to integrin αIIbβ3 function. Future studies will focus on exploring a potential role of TNIK in the regulation of thrombosis and hemostasis in vivo to assess TNIK’s potential as a novel antithrombotic target.

•TRAF2 and NCK interacting kinase (TNIK) is a serine/threonine kinase with no currently known role in platelets.•TNIK function was explored in platelets using 2 structurally distinct inhibitors.•Inhibition of TNIK reduces markers of platelet integrin signaling.•TNIK may be a novel antiplatelet target.

TRAF2 and NCK interacting kinase (TNIK) is a serine/threonine kinase with no currently known role in platelets.

TNIK function was explored in platelets using 2 structurally distinct inhibitors.

Inhibition of TNIK reduces markers of platelet integrin signaling.

TNIK may be a novel antiplatelet target.