The interaction between XBP1 and eNOS contributes to endothelial cell migration.

The X-box binding protein 1 (XBP1) is a pivotal transcription factor in the endoplasmic reticulum stress response. Our previous studies have proven that XBP1 is involved in vascular endothelial growth factor (VEGF)-mediated endothelial cell (EC) proliferation and angiogenesis. In this study, we used EC monolayer wound healing, tube formation and transwell migration models to explore the role of XBP1splicing in EC migration. We found that scratching on EC monolayer triggered XBP1splicing, which was attenuated by the presence of SU5416and LY294002, suggesting that VEGF signalling pathways may be involved. Over-expression of the spliced XBP1 (XBP1s) via Ad-XBP1s gene transfer increased while knockdown of IRE1αor XBP1 by ShRNA lentivirus suppressed EC migration. Over-expression of XBP1s up-regulated the nitric oxide synthase 3 (NOS3)mRNA through the 3'UTR-mediated stabilisation and increased eNOS protein translation. Further experiments demonstrated that miR-24 participated in the XBP1s-induced eNOSup-regulation and EC migration. Further co-IP and immunofluorescence staining assays revealed that protein kinase B (Akt), eNOS andXBP1s form a complex, resulting in Akt and eNOS nucleus relocation. These results suggest that XBP1 splicing can regulate eNOS expression and cellular location, leading to EC migration and therefore contributing to wound healing and angiogenesis.