CD81 Is Essential for the Re-entry of Hematopoietic Stem Cells to Quiescence following Stress-Induced Proliferation Via Deactivation of the Akt Pathway
Figure 4
CD81 monoclonal antibody triggers early cell cycle exit.
(A) EAT2, a CD81 monoclonal antibody, induces clustering of CD81 on regenerating HSCs (5FU-Day7). With CD81 antibody treatment, the localization of CD81 protein on the wild-type HSC cell membrane shows a distinctively polarized pattern; whereas with the isotype control antibody, the pattern consists of diffuse punctuate dots. (B) The distribution of CD81 on EAT2-treated HSCs is significantly compressed by comparison with the isotype control. In this assay, single cell images were acquired, and the area of CD81 in every acquired image was measured with ImageJ. Horizontal bars denote medium values. Mean values ± SD are shown (***p<0.001). (C) Engagement of CD81 proteins on proliferating HSCs (5FU-Day7) with EAT2 induces a significant fraction of HSC to enter quiescence. Ki-67 staining was used to identify proliferating HSCs. Proportions of quiescent cells are given within the graph. (D) EAT2 induces cell cycle exit. HSCs stimulated with 5FU were treated with EAT2 or hamster IgG (n = 3 per group) and assessed for Ki-67 reactivity on day 7 post-treatment. Mean percentages ± SD are shown (*p<0.05).