Kurano Makoto, Nishikawa Masako, Kuma Hiroyuki, Jona Masahiro, Yatomi Yutaka
Department of Clinical Laboratory Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
Department of Clinical Chemistry, Faculty of Pharmaceutical Sciences, Nagasaki International University, Nagasaki, Japan.
PLoS One. 2017 May 11;12(5):e0177543. doi: 10.1371/journal.pone.0177543. eCollection 2017.
Sphingosine 1-phosphate (S1P) is a bioactive lipid mediator that is thought to be involved in various diseases. Although the main source of S1P in the plasma is erythrocytes, how S1P is exported from erythrocytes has not been elucidated. When we differentiated K562 cells into erythroblast-like cells with sodium butyrate, we observed that the efflux of S1P was increased without increased expression of previously proposed S1P transporters, while the expression levels of Band3 were increased. Therefore, in this study, we investigated the involvement of Band 3, the most characteristic membranous transporter for erythrocytes, in S1P efflux, using 4,4'-diisothiocyanatodihydrostilbene-2,2'-disulfonic acid, disodium salt (H2DIDS), which is an inhibitor of Band3. First, we treated human washed erythrocytes with H2DIDS and found that H2DIDS decreased the S1P levels in the supernatant, while it increased the cellular S1P contents. Next, when we injected H2DIDS into mice, the plasma S1P level was significantly decreased. Finally, when we overexpressed or suppressed Band3 in K562 cells, S1P efflux was enhanced or decreased, respectively, while the overexpression of Band3 in HEK293 cells did not modulate S1P efflux. These results suggested the possible involvement of Band3 in the transport of S1P, a multi-functional bioactive phospholipid, from erythrocytes.
鞘氨醇-1-磷酸（S1P）是一种生物活性脂质介质，被认为与多种疾病有关。虽然血浆中S1P的主要来源是红细胞，但S1P如何从红细胞中输出尚未阐明。当我们用丁酸钠将K562细胞分化为成红细胞样细胞时，我们观察到S1P的流出增加，而先前提出的S1P转运蛋白的表达并未增加，同时Band3的表达水平增加。因此，在本研究中，我们使用Band3抑制剂4,4'-二异硫氰酸二氢芪-2,2'-二磺酸二钠盐（H2DIDS）研究了红细胞最具特征性的膜转运蛋白Band3在S1P流出中的作用。首先，我们用H2DIDS处理人洗涤红细胞，发现H2DIDS降低了上清液中的S1P水平，同时增加了细胞内S1P含量。接下来，当我们给小鼠注射H2DIDS时，血浆S1P水平显著降低。最后，当我们在K562细胞中过表达或抑制Band3时，S1P流出分别增强或降低，而在HEK293细胞中过表达Band3并未调节S1P流出。这些结果表明Band3可能参与了多功能生物活性磷脂S1P从红细胞的转运。
