Giepmans B N, Verlaan I, Moolenaar W H
Division of Cellular Biochemistry, The Netherlands Cancer Institute and Center for Biomedical Genetics, Amsterdam.
Cell Commun Adhes. 2001;8(4-6):219-23. doi: 10.3109/15419060109080727.
Gap junctions are composed of connexins that form transmembrane channels between adjacent cells. The C-terminal tail of connexin-43 (Cx43), the most widely expressed connexin member, has been implicated in the regulation of Cx43 channel gating. Interestingly, channel-independent processes regulated by Cx43 have also been postulated. In our studies to elucidate the mechanism of Cx43 channel gating by growth factors and to explore additional functions of gap junctions, we have identified three interacting partners of the C-terminal tail of Cx43 (Cx43CT). (i) the c-Src tyrosine kinase, which phosphorylates Cx43CT and is involved in G protein-mediated inhibition of Cx43 gap junctional communication. (ii) the ZO-1 'scaffold' protein, which might recruit signaling proteins into Cx43-based gap junctions. (iii) microtubules (consisting of alpha/beta-tubulin dimers), which extend with their distal ends to Cx43-based gap junctions, suggesting that Cx43 gap junctions may play a novel role in regulating microtubule stability in contacted cells. Here we show that Cx43 binds alpha-tubulin equally well as beta-tubulin. In addition, we show that the second, but not the first, PDZ domain of ZO-1 binds directly to Cx43, and we confirm that the very C-terminal isoleucine residue of Cx43 is critical for ZO-1 binding.
间隙连接由连接蛋白组成，这些连接蛋白在相邻细胞之间形成跨膜通道。连接蛋白-43（Cx43）是表达最为广泛的连接蛋白成员，其C末端尾巴参与了Cx43通道门控的调节。有趣的是，也有人推测Cx43可调节与通道无关的过程。在我们旨在阐明生长因子对Cx43通道门控的作用机制以及探索间隙连接其他功能的研究中，我们鉴定出了Cx43 C末端尾巴（Cx43CT）的三个相互作用伙伴。（i）c-Src酪氨酸激酶，它使Cx43CT磷酸化，并参与G蛋白介导的对Cx43间隙连接通讯的抑制。（ii）ZO-1“支架”蛋白，它可能将信号蛋白招募到基于Cx43的间隙连接中。（iii）微管（由α/β-微管蛋白二聚体组成），其远端延伸至基于Cx43的间隙连接，这表明Cx43间隙连接可能在调节接触细胞中的微管稳定性方面发挥新作用。在此我们表明，Cx43与α-微管蛋白和β-微管蛋白的结合能力相当。此外，我们表明，ZO-1的第二个而非第一个PDZ结构域直接与Cx43结合，并且我们证实Cx43的最末端异亮氨酸残基对于与ZO-1的结合至关重要。
