# The nonconserved integrin cytoplasmic region determines integrin subtype–specific characteristics by modulating talin1 binding kinetics

## TL;DR

A specific region in integrin's cytoplasmic tail, the WN linker, controls how tightly talin1 binds to integrins, affecting cell adhesion and signaling.

## Contribution

The WN linker is identified as a novel regulator of integrin–talin binding strength and adhesiveness diversity.

## Key findings

- Talin1 binds more strongly to β2 integrin than β7 due to differences in the WN linker sequence.
- The NND sequence in β2 integrins enhances talin1 binding, while KQDS in β7 integrins weakens it.
- The second asparagine in NND is crucial for talin1 binding and is conserved only in mammalian β2 integrins.

## Abstract

Talin governs integrin adhesion by binding to the cytoplasmic tail of integrin β subunits, but the effects of integrin subtype–specific variations on talin interactions remain unclear. Here, we identify a nonconserved region within the cytoplasmic tail of integrin, termed the WN linker, that modulates talin1 binding kinetics and integrin adhesiveness. Single-molecule imaging in live lymphocytes revealed that talin1 bound more strongly to β2 than β7 integrin, with higher off-rates in β7 in vivo. This difference was due to the unique NND sequence in the β2 WN linker compared with KQDS in the β7 WN linker. Structural and biochemical analyses showed that NND established a tighter interaction with talin, whereas KQDS bent, narrowing the interaction area and weakening the interaction. Substituting the NND sequence in β2 with KQDS impaired inside–out signaling– and ligand binding–induced conformational activation of LFA1. Multiple sequence alignment and single-molecule binding analyses revealed that the NND sequence is highly conserved only in mammalian β2 integrins, and that the second asparagine in NND, a residue absent in nonmammalian β2 integrins and other integrins, plays a key role in talin1 binding. Parallel observations in β3 integrins reinforced the pivotal role of the WN linker in modulating integrin–talin affinity. These observations highlight the WN linker as a novel regulator of integrin–talin binding strength and adhesiveness diversity.