Promotion of lens epithelial-fiber differentiation by the C-terminus of connexin 45.6 - a role independent of gap junction communication
Promotion of lens epithelial-fiber differentiation by the C-terminus of connexin 45.6 - a role independent of gap junction communication
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DOI：
10.1242/jcs.000935
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发表时间：
2007-10-15
影响因子：
4
通讯作者：
Jiang, Jean X.
中科院分区：
文献类型：
--
作者：
Banks, Eric A.;Yu, X. Sean;Jiang, Jean X.
我们以前曾报道，在鸡晶状体中表达的三种连接蛋白中，连接蛋白(Cx)45.6的过度表达促进了晶状体细胞的分化，而不是Cx43或Cx56；然而，导致这种作用的潜在机制尚不清楚。在这里，我们利用了自然发生的CX50(鸡Cx45.6的直系)的缝隙连接功能缺失突变，并在Cx45.6中产生了相应的位点突变：Cx45.6(D47A)和Cx45.6(P88S)。与野生型Cx45.6不同，突变体Cx45.6(P88S)和Cx45.6(D47A)不能形成功能性缝隙连接，并且Cx45.6(D47A)以显性-负性方式起作用。有趣的是，两个不能形成缝隙连接的突变体的过表达显著增加了上皮-纤维分化，达到了与野生型Cx45.6相当的水平。为了定位Cx45.6的功能结构域，我们产生了一个C末端嵌合体和一个缺失突变体。Cx56的C端被Cx45.6取代的突变体Cx56*45.6C过表达对晶状体细胞分化的刺激作用与Cx45.6相似。然而，过表达Cx45.6*56C和Cx45.6(-C)的细胞不能促进分化。综上所述，我们认为Cx45.6的表达，而不是Cx45.6依赖的缝隙连接通道，参与了晶状体上皮-纤维细胞的分化，Cx45.6的C-末端结构域在这一过程中起着主导作用。
We previously reported that, among the three connexins expressed in chick lens, overexpression of connexin ( Cx) 45.6, not Cx43 or Cx56, stimulates lens cell differentiation; however, the underlying mechanism responsible for this effect is unclear. Here, we took advantage of naturally occurring loss- of- gap- junction function mutations of Cx50 ( ortholog of chick Cx45.6) and generated the corresponding site mutants in Cx45.6: Cx45.6( D47A) and Cx45.6( P88S). In contrast to wild- type Cx45.6, the mutants failed to form functional gap junctions, and Cx45.6( P88S) and, to a lesser degree, Cx45.6( D47A) functioned in a dominant- negative manner. Interestingly, overexpression of both mutants incapable of forming gap junctions significantly increased epithelial- fiber differentiation to a level comparable to that of wild- type Cx45.6. To map the functional domain of Cx45.6, we generated a C- terminus chimera as well as deletion mutants. Overexpression of Cx56* 45.6C, the mutant in which the C- terminus of Cx56 was replaced with that of Cx45.6, had a stimulatory effect on lens cell differentiation similar to that of Cx45.6. However, cells overexpressing Cx45.6* 56C, the mutant in which C- terminus of Cx45.6 was replaced with that of Cx56, and Cx45.6( - C), in which the C- terminus was deleted, failed to promote differentiation. Taken together, we conclude that the expression of Cx45.6, but not Cx45.6dependent gap junction channels, is involved in lens epithelial- fiber cell differentiation, and the C- terminal domain of Cx45.6 plays a predominant role in mediating this process.