# Syntaxin 4 protects islet β-cells from cytokine-induced senescence

## TL;DR

This study shows that Syntaxin 4 protects pancreatic beta cells from aging caused by stress, which could help treat type 1 diabetes.

## Contribution

The study reveals Syntaxin 4 as a novel cytoprotective factor against cytokine-induced β-cell senescence in type 1 diabetes.

## Key findings

- STX4 overexpression reduced p21 and γH2AX accumulation in β-cells under stress.
- In NOD mice, STX4 preserved nuclear Lamin B1 and reduced senescence markers.
- STX4 reshaped the β-cell secretome and repressed senescence-related transcriptional programs.

## Abstract

Type 1 diabetes (T1D) is characterized by progressive loss of pancreatic b-cell function, which is accelerated by cytokine-induced senescence and the accompanying senescence-associated secretory phenotype (SASP). We investigated whether Syntaxin 4 (STX4), a t-SNARE protein previously recognized for its cytoprotective properties, can mitigate b-cell senescence under diabetogenic stress.

Ectopic STX4 expression was induced in MIN6 cells, human islets, and murine islets, followed by cytokine and bleomycin treatment to model senescence-inducing stress and subsequent quantification of senescence markers (p21 and γH2AX). b-cell specific STX4 expression was induced in the non-obese diabetic (NOD) mice and senescence-markers, including p21, γH2AX, and nuclear Lamin B, were subsequently quantified. In parallel, we analyzed single-cell RNA sequencing and performed conditioned-medium proteomics to define STX4-dependent transcriptional and secretome changes, respectively.

STX4 overexpression markedly reduced cytokine-induced accumulation of p21 and γH2AX in MIN6 cells, human islets, and murine islets. In NOD mice, induced STX4 expression reduced p21 and γH2AX accumulation and preserved nuclear Lamin B1 in pancreatic b-cells, supporting an in vivo senoprotective effect. Integrated transcriptomics and proteomics analyses showed that STX4 represses senescence-related transcriptional programs and reshapes the β-cell secretome, including enrichment of proteins involved in purine ribonucleotide metabolism.

These findings indicate that STX4 protects β-cells from cytokine or bleomycin-induced senescence and suggest that enhancing STX4 activity may be a therapeutic strategy to preserve functional β-cell mass in T1D.