# β2-Integrins regulate dendritic cells through nuclear deformation and activation of phospholipase A2 and DNA damage–inducible GADD34

## TL;DR

This study shows how β2-integrins control dendritic cell activation through nuclear deformation and a specific signaling pathway involving cPLA2 and GADD34.

## Contribution

The paper reveals a novel mechanical signaling pathway linking β2-integrin adhesion, nuclear deformation, and DC activation via cPLA2 and GADD34.

## Key findings

- Loss of β2-integrin adhesion and nuclear deformation upregulate DC activation markers like Ccr7, Cd86, and Il12b.
- cPLA2 inhibition rescues EIF2α phosphorylation and reduces interleukin-12 and CD86 in β2-integrin-deficient BMDCs.
- GADD34 inhibition decreases DC activation markers in β2-integrin-deficient BMDCs.

## Abstract

Dendritic cells (DCs) reside in tissues and are activated by danger or pathogen-associated signals, leading to expression of costimulatory markers and cytokines, downregulation of β2-integrin–mediated adhesion, migration to lymph nodes, and activation of T cells. Conversely, β2-integrins are known to restrict DC activation and migration, but signaling pathways involved in this process remain poorly understood. Here, we show that β2-integrins regulate podosome formation as well as nuclear morphology of bone marrow–derived DCs (BMDCs) on both stiff and soft surfaces. Analysis of published gene expression data revealed that loss of β2-integrin adhesion and nuclear deformation both upregulate DC activation markers and cytokines, including Ccr7, Cd86, and Il12b. Growth arrest and DNA damage–inducible protein (GADD34; Ppp1r15) of the unfolded protein responses was also upregulated in both datasets. Utilizing a cytosolic phospholipase A2 (cPLA2) inhibitor, we show that the nuclear shape sensor cPLA2 controls interleukin-12 production and CD86 expression of β2-integrin adhesion–deficient BMDCs. We further show that the GADD34 pathway is activated in adhesion-deficient BMDCs, as eukaryotic translation initiation factor 2A (EIF2α) phosphorylation is reduced in these cells, whilst cPLA2 inhibition rescues EIF2α phosphorylation. Furthermore, GADD34 inhibition led to decreased interleukin-12 production and CD86 expression in β2-integrin–deficient BMDCs, whilst inhibition of protein kinase R–like endoplasmic reticulum kinase (the canonical EIF2α kinase) had no effect. Together, our results show that loss of β2-integrin adhesion leads to nuclear deformation and activation of a cPLA2–GADD34 pathway in BMDCs, which at least partly controls their activated phenotype. Our results therefore reveal how cell adhesion and nuclear deformation are connected to mechanically control DC activation.