Sosne Gabriel, Xu Lihua, Prach Lisa, Mrock Linda K, Kleinman Hynda K, Letterio John J, Hazlett Linda D, Kurpakus-Wheater Michelle
Department of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, MI 48201, USA.
Exp Cell Res. 2004 Feb 1;293(1):175-83. doi: 10.1016/j.yexcr.2003.09.022.
Thymosin beta 4 (Tbeta(4)) stimulates epithelial cell migration and promotes laminin-5 (LM-5) expression. Using gene expression analysis with human corneal epithelial cells treated with Tbeta(4), we find that both LM-5 gamma2 chain and transforming growth factor beta 1 (TGFbeta-1) are increased by more than 2-fold over untreated cells. These findings were confirmed by RT-PCR and at the protein level. Although TGFbeta-1 increases LM-5 synthesis in a dose-dependent manner, it does not appear to be the mechanism by which Tbeta(4) acts on LM-5 gamma2 chain synthesis based on three independent experiments. In a time-course analysis, Tbeta(4) increases LM-5 gamma2 chain expression at 2 h and peaks at 6 h, while TGFbeta-1 increases LM-5 gamma2 chain expression only at 4 h and peaks at 8 h. When Tbeta(4)-induced LM-5 gamma2 chain expression is blocked with neutralizing antibodies to TGFbeta-1, LM-5 gamma2 chain expression is increased. Finally, in TGFbeta-1 knock-out mice, Tbeta(4) increases LM-5 gamma2 chain expression to levels higher than that observed in wild-type mice treated with Tbeta(4). These findings demonstrate that Tbeta(4) induces both TGFbeta-1 and LM-5 gamma2 chain expression in corneal epithelial cells. Tbeta(4) and TGFbeta-1 increase LM-5 gamma2 chain expression by independent pathways. Suppression of TGFbeta-1 further increases LM-5 gamma2 chain expression.
胸腺素β4（Tbeta(4)）可刺激上皮细胞迁移并促进层粘连蛋白-5（LM-5）的表达。通过对用Tbeta(4)处理的人角膜上皮细胞进行基因表达分析，我们发现与未处理的细胞相比，LM-5γ2链和转化生长因子β1（TGFbeta-1）均增加了两倍以上。这些发现通过逆转录聚合酶链反应（RT-PCR）和蛋白质水平得到了证实。尽管TGFbeta-1以剂量依赖性方式增加LM-5的合成，但基于三项独立实验，它似乎不是Tbeta(4)作用于LM-5γ2链合成的机制。在时间进程分析中，Tbeta(4)在2小时时增加LM-5γ2链的表达，并在6小时时达到峰值，而TGFbeta-1仅在4小时时增加LM-5γ2链的表达，并在8小时时达到峰值。当用抗TGFbeta-1的中和抗体阻断Tbeta(4)诱导的LM-5γ2链表达时，LM-5γ2链的表达增加。最后，在TGFbeta-1基因敲除小鼠中，Tbeta(4)将LM-5γ2链的表达增加到高于用Tbeta(4)处理的野生型小鼠所观察到的水平。这些发现表明，Tbeta(4)在角膜上皮细胞中诱导TGFbeta-1和LM-5γ2链的表达。Tbeta(4)和TGFbeta-1通过独立的途径增加LM-5γ2链的表达。抑制TGFbeta-1会进一步增加LM-5γ2链的表达。
