Graduate School of Nanobioscience, Yokohama City University, 22-2 Seto, Kanazawa-ku, Yokohama, 236-0027, Japan.
Graduate School of Nanobioscience, Yokohama City University, 22-2 Seto, Kanazawa-ku, Yokohama, 236-0027, Japan; Ichiban Life Corporation, 1-1-7 Horai-cho, Naka-ku, Yokohama, 231-0048, Japan.
Exp Cell Res. 2020 May 1;390(1):111927. doi: 10.1016/j.yexcr.2020.111927. Epub 2020 Feb 29.
Cellular senescence is a phenomenon of irreversible growth arrest of mammalian somatic cells. Senescent cells increase the production of secretory proteins such as inflammatory cytokines, a phenomenon termed senescence-associated secretory phenotype (SASP). SASP is known to have profound effects on organismal health and aging; however, the molecular mechanisms of SASP are not precisely understood. In our previous studies, we have shown that senescent cells show decreased function of lamin B receptor (LBR), a nuclear membrane protein that regulates heterochromatin organization. Here we examined the implication of LBR in the regulation of SASP because senescent cells show altered heterochromatin organization, which would affect gene expression. We found that knock-down of LBR up-regulated the expression of the SASP factors such as IL-6, IL-8, and MMP1 in HeLa cells, even though cellular senescence was not induced by LBR knock-down. Conversely, enforced expression of LBR suppressed their up-regulated expression in senescent cells induced by excess thymidine. Further, our gene expression profile analysis also showed that many secretory proteins were up-regulated by LBR knock-down. We then analyzed the regulatory mechanisms of the expression of SASP factors by LBR, and found that the promoters of these SASP factors associated with LBR in normally growing cells, but dissociated from it in senescent cells. Additionally, we found that enforced expression of LBR decreased the generation of cytoplasmic DNA, which could be involved in SASP, in senescent cells. These findings suggested that LBR would play crucial roles in the regulation of SASP.
细胞衰老是哺乳动物体细胞不可逆生长停滞的现象。衰老细胞会增加分泌蛋白的产生，如炎性细胞因子，这种现象被称为衰老相关分泌表型（SASP）。SASP 已知对机体健康和衰老有深远影响；然而，SASP 的分子机制尚不完全清楚。在我们之前的研究中，我们已经表明衰老细胞显示出核膜蛋白 lamin B 受体（LBR）的功能降低，LBR 调节异染色质组织。在这里，我们研究了 LBR 在调节 SASP 中的作用，因为衰老细胞显示出异染色质组织的改变，这会影响基因表达。我们发现，即使不通过 LBR 敲低诱导衰老细胞，LBR 的敲低也会上调 HeLa 细胞中 SASP 因子（如 IL-6、IL-8 和 MMP1）的表达。相反，过量胸苷诱导的衰老细胞中 LBR 的强制表达抑制了它们的上调表达。此外，我们的基因表达谱分析还表明，许多分泌蛋白被 LBR 敲低上调。然后，我们分析了 LBR 对 SASP 因子表达的调控机制，发现这些 SASP 因子的启动子在正常生长的细胞中与 LBR 相关联，但在衰老细胞中与之分离。此外，我们发现，LBR 的强制表达减少了衰老细胞中与 SASP 相关的细胞质 DNA 的产生。这些发现表明 LBR 将在 SASP 的调节中发挥关键作用。
