ObjectiveTo investigate whether the CD151 YXXφ motif point mutant affects vascular permeability by regulating vesicle internalization and recycling. MethodsCD151 knockout （KO） and wild-type （WT） mice were used. A modified Miles assay was performed to compare vascular permeability in the dorsal and postauricular skin of the two groups of mice under vascular endothelial growth factor A （VEGF-A） stimulation. The CD151 YXXφ motif point mutant YALA was constructed and transfected into human endothelial cells （EA.hy926） using an adenoviral vector. Multiple experimental groups were set up to detect the permeability of endothelial cell monolayers to FITC-dextran under baseline conditions and after VEGF-A stimulation. Western blot （WB）， RT-qPCR， and immunofluorescence were used to examine the expression and distribution of VE-cadherin. The internalization rate of VE-cadherin was quantitatively compared using a cell surface biotinylation assay. Phalloidin was used to label F-actin to observe changes in cytoskeletal tension. ResultsThe Miles assay showed that under VEGF-A stimulation， dye extravasation in the dorsal and postauricular skin of KO mice was significantly higher than that in WT mice （all P<0.05）. At 60 min and 120 min after VEGF-A stimulation， the permeability of endothelial cell monolayers overexpressing the YALA mutant to FITC-dextran significantly increased （P<0.05）. WB and RT-qPCR results indicated that the YALA mutant did not affect the total protein or mRNA expression levels of VE-cadherin. Immunofluorescence revealed that the YALA mutant disrupted the continuous distribution of VE-cadherin on the cell membrane and its perinuclear co-localization with CD151 under VEGF-A stimulation. The cell surface biotinylation assay confirmed that the YALA mutant significantly reduced the internalization rate of VE-cadherin （P<0.05）. Cytoskeletal staining showed that the YALA mutant caused the formation of thick tension fibers in the actin cytoskeleton of endothelial cells， indicating cell contraction. ConclusionThe CD151 YXXφ motif point mutation affects vesicle internalization and recycling in endothelial cells， influences the expression and internalization of VE-cadherin， and consequently affects vascular permeability.

Objective : To explore the effect and mechanism of CD151 on vascular permeability by regulating vesicle internalization and recycling. Methods: Wild-type mice and CD151 knockout mice were divided into WT-con group, WT-model group, KO-con group and KO-model group, with 6 mice in each group. WT-model group and KO-model group were intraperitoneally injected with LPS to prepare sepsis ALI model, and WT-con group and KO-con group were intraperitoneally injected with phosphate buffer saline(PBS) as a control. 24 h after modeling, pulmonary vascular permeability was measured by Miles test. The siRNA silencing CD151 expression(si-CD151) and negative control si-NC were transfected into EA.hy 926 cells. The permeability of endothelial cell layer to FITC-dextran at different time points was observed under basic conditions and vascular endothelial growth factor-A(VEGF-A) stimulation conditions. Transcriptome sequencing of endothelial cells in si-CD151 group and si-NC group; the distribution and internalization of CD151 in each group were measured using immunofluorescence. Western blot and real-time quantitative RT-qPCR were used to detect the expression of VE-cadherin in si-CD151 groupand other groups. The distribution and internalization of VE-cadherin in each group were measured using immunofluorescence. Results : Miles experiment results indicated that dye exudation in lung tissue of WT-model group was significantly higher than that of WT-con group(P<0.01). The dye exudation in the lung tissue of KO-model group increased compared with WT-model group(P<0.05). The results of endothelial cell layer permeability test showed that the permeability of FITC-dextran in si-CD151 group was significantly higher than that in control group after VEGF-A stimulation for 30, 60 and 120 min(P<0.05). Transcriptome sequencing results suggested that CD151 in endothelial cells was closely related to vesicle-mediated transport. Compared with other groups, protein and mRNA levels of VE-cadherin in CD151 knockdown endothelial cells was significantly lower(allP<0.01). The immunofluorescence assay demonstrated that after VEGF-A stimulation, the decrease of CD151 expression significantly impaired the expression of VE-cadherin at cell-cell contacts and reduced the CD151-VE-cadherin colocalization in the perinuclear region compared with other groups. Conclusion The absence of CD151 affects the internalization and recycling of endothelial cell vesicles, affects the expression and internalization of VE-cadherin, and then influences vascular permeability.