Bhowmick Diti Chatterjee, Ahn Miwon, Bhattacharya Supriyo, Aslamy Arianne, Thurmond Debbie C
Department of Molecular and Cellular Endocrinology, Arthur Riggs Diabetes and Metabolism Research Institute, Beckman Research Institute of City of Hope, Duarte, CA, USA.
Department of Molecular and Cellular Endocrinology, Arthur Riggs Diabetes and Metabolism Research Institute, Beckman Research Institute of City of Hope, Duarte, CA, USA.
Metabolism. 2025 Mar;164:156132. doi: 10.1016/j.metabol.2025.156132. Epub 2025 Jan 11.
Type 1 diabetic human islet β-cells are deficient in double C 2 like domain beta (DOC2b) protein. Further, DOC2b protects against cytokine-induced pancreatic islet β-cell stress and apoptosis. However, the mechanisms underpinning the protective effects of DOC2b remain unknown.
Biochemical studies, qPCR, proteomics, and immuno-confocal microscopy were conducted to determine the underlying protective mechanisms of DOC2b in β-cells. DOC2b-enriched or -depleted primary islets (human and mouse) and β-cell lines challenged with or without proinflammatory cytokines, global DOC2b heterozygous knockout mice subjected to multiple-low-dose-streptozotocin (MLD-STZ), were used for these studies.
A significant elevation of stress-induced CXCL10 mRNA was observed in DOC2b-depleted β-cells and primary mouse islets. Further, DOC2b enrichment markedly attenuated cytokine-induced CXCL10 levels in primary non-diabetic human islets and β-cells. DOC2b enrichment also reduced total-NF-κB p65 protein levels in human islets challenged with T1D mimicking proinflammatory cytokines. IKKβ, NF-κB p65, and STAT-1 are capable of associating with DOC2b in cytokine-challenged β-cells. DOC2b enrichment in cytokine-stressed human islets and β-cells corresponded with a significant reduction in activated and total IKKβ protein levels. Total IκBβ protein was increased in DOC2b-enriched human islets subjected to acute cytokine challenge. Cytokine-induced activated and total STAT-1 protein and mRNA levels were markedly reduced in DOC2b-enriched human islets. Intriguingly, DOC2b also prevents ER-stress-IKKβ and STAT-1 crosstalk in the rat INS1-832/13 β-cell line.
The mechanisms underpinning the protective effects of DOC2b involve attenuation of IKKβ-NF-κB p65 and STAT-1 signaling, and reduced CXCL10 expression.
1型糖尿病患者的胰岛β细胞中双C2样结构域β（DOC2b）蛋白缺乏。此外，DOC2b可保护胰岛β细胞免受细胞因子诱导的应激和凋亡。然而，DOC2b发挥保护作用的机制尚不清楚。
进行了生化研究、qPCR、蛋白质组学和免疫共聚焦显微镜检查，以确定DOC2b在β细胞中的潜在保护机制。这些研究使用了富含或缺乏DOC2b的原代胰岛（人和小鼠）以及β细胞系，它们分别受到或未受到促炎细胞因子的刺激，还使用了接受多次低剂量链脲佐菌素（MLD-STZ）处理的全球DOC2b杂合敲除小鼠。
在缺乏DOC2b的β细胞和原代小鼠胰岛中，观察到应激诱导的CXCL10 mRNA显著升高。此外，在原代非糖尿病人类胰岛和β细胞中，富集DOC2b可显著降低细胞因子诱导的CXCL10水平。在受到模拟1型糖尿病的促炎细胞因子刺激的人类胰岛中，富集DOC2b还可降低总NF-κB p65蛋白水平。在受到细胞因子刺激的β细胞中，IKKβ、NF-κB p65和STAT-1能够与DOC2b结合。在受到细胞因子应激的人类胰岛和β细胞中，富集DOC2b与活化的和总的IKKβ蛋白水平显著降低相对应。在受到急性细胞因子刺激的富含DOC2b的人类胰岛中，总IκBβ蛋白增加。在富含DOC2b的人类胰岛中，细胞因子诱导的活化的和总的STAT-1蛋白及mRNA水平显著降低。有趣的是，DOC2b还可防止大鼠INS1-832/13β细胞系中内质网应激-IKKβ和STAT-１的相互作用。
DOC2b发挥保护作用的机制包括减弱IKKβ-NF-κB p65和STAT-1信号传导以及降低CXCL10表达。
