Institute of Bioengineering and Nanotechnology, 31 Biopolis Way, The Nanos, #04-01, Singapore 138669, Singapore.
Eur J Cell Biol. 2009 Dec;88(12):719-30. doi: 10.1016/j.ejcb.2009.08.003. Epub 2009 Sep 24.
Intercellular communication is an important tool used by the cells to effectively regulate concerted responses. Hepatic stellate cells (HSCs) communicate to each other through functional gap junctions composed of connexin 43 (Cx43) proteins. We show that exogenous human TGF-beta1 (hTGF-beta1), a pro-fibrotic stimulus, decreases Cx43 mRNA and protein in a rat HSC cell line and primary HSCs. Furthermore, hTGF-beta1 increases the phosphorylation of Cx43 at serine 368. These effects lead to a decrease in the gap junction intercellular communication between the HSCs, as shown by gap-FRAP analysis. We also observe the binding of Snai1, from the nuclear extract of HSCs, to a Snai1 consensus sequence in the Cx43 promoter. In the same context, Snai1 siRNA transfection results in an up-regulation of Cx43 suggesting that TGF-beta1 may regulate Cx43 via Snai1. In addition, we demonstrate that the knockdown of Cx43 by siRNA transfection results in a slower proliferation of HSCs. These findings illuminate a new effect of TGF-beta1 in HSCs, namely the regulation of intercellular communication by affecting the expression level and the phosphorylation state of Cx43 through Snai1 signaling.
细胞间通讯是细胞有效调节协同反应的重要工具。肝星状细胞 (HSCs) 通过由连接蛋白 43 (Cx43) 蛋白组成的功能性间隙连接相互通讯。我们表明，外源性人 TGF-β1（hTGF-β1），一种促纤维化刺激物，可降低大鼠 HSC 细胞系和原代 HSCs 中的 Cx43 mRNA 和蛋白。此外，hTGF-β1 增加 Cx43 在丝氨酸 368 处的磷酸化。这些效应导致 HSCs 之间的间隙连接细胞间通讯减少，如间隙 FRAP 分析所示。我们还观察到来自 HSCs 核提取物的 Snai1 与 Cx43 启动子中的 Snai1 共有序列结合。在相同的情况下，Snai1 siRNA 转染导致 Cx43 的上调，表明 TGF-β1 可能通过 Snai1 调节 Cx43。此外，我们证明通过 siRNA 转染敲低 Cx43 可导致 HSCs 的增殖速度减慢。这些发现阐明了 TGF-β1 在 HSCs 中的新作用，即通过影响 Cx43 的表达水平和磷酸化状态来调节细胞间通讯，这是通过 Snai1 信号传导实现的。
