ANALYSIS OF CONNEXIN26 IN MOUSE SKIN CARCINOGENESIS

连接蛋白26在小鼠皮肤癌变中的作用分析本项目的主要目的是研究缝隙连接蛋白（connexins, Cx）控制细胞生长的一种基本的、新颖的分子机制。大量证据表明，连接蛋白基因是肿瘤抑制基因，因为连接蛋白功能的丧失或改变为细胞提供了生长优势。然而，现在已经很好地理解了一些连接蛋白，特别是来自所谓的α和β基团的连接蛋白是不相容的。由不相容连接组成的半通道不能形成功能性通道。这使我们提出了一种假设，即不相容连接蛋白的共表达实际上可能会减少间隙连接细胞间通讯（GJIC），从而在癌变过程中释放连接蛋白介导的细胞生长控制。本项目的主要目的是利用不相容的Cx26 （beta2）和Cx43 （alpha1）在角质形成细胞中的共表达模型来验证这一创新假设。我的实验室对正常小鼠皮肤和皮肤肿瘤中连接蛋白表达的综合分析表明，Cx26/Cx43组合在皮肤肿瘤促进过程中具有特殊作用。成年小鼠表皮角质形成细胞表达多种连接蛋白，包括Cx43，但不表达Cx26。在90%的皮肤乳头状瘤中，我们观察到连接蛋白表达谱的整体简化，并向仅表达两种主要连接蛋白Cx26和Cx43的转变，这两种连接蛋白共同定位于转化角化细胞的质膜上。为了探讨Cx26/Cx43共表达在皮肤肿瘤发病中的致病作用，我们设计了以下具体目的：1)确定不相容连接蛋白Cx26和Cx43共表达是否抑制角化细胞中的GJIC；2)确定不相容连接蛋白Cx26和Cx43的共表达是否对角质形成细胞有生长优势；3)在表皮中培养缺乏Cx26表达的转基因动物，并将Cx26靶向cx43阳性的基底角质形成细胞。这些实验的结果对于破译连接蛋白控制生长的其他机制具有重要意义。

Analysis of connexin26 role in mouse skin carcinogenesis.. The primary objective of this project is to study a fundamental and novel molecular mechanism of cell growth control by gap junctional proteins, the connexins (Cx). Considerable evidence indicates that connexin genes are tumor suppressor genes since loss or change of connexin function provides a growth advantage to cells. However, it is well understood now that some connexins, especially connexins from so-called alpha and beta groups are incompatible. Hemi-channels composed from incompatible connexins do not form functional channels. This led us to the hypothesis that Co- expression of incompatible connexins may actually decrease gap junctional intercellular communication (GJIC), thereby releasing cells from connexin-mediated growth control during carcinogenesis. The primary objective of this project is to test this innovative hypothesis using as a model co-expression of incompatible Cx26 (beta2) and Cx43 (alpha1) in keratinocytes. The comprehensive analysis of connexin expression in normal mouse skin and in skin tumors, by my laboratory, indicated an exceptional role for Cx26/Cx43 combination during skin tumor promotion. Keratinocytes in adult mouse epidermis express several connexins including Cx43 but not Cx26. In 90% of skin papillomas we observed the overall simplification of connexin expression profile with a shift towards expression of only two major connexins, Cx26 and Cx43, which were co- localized on the plasma membranes of transformed keratinocytes. To investigate the causative role of Cx26/Cx43 Co-expression in the pathogenesis of skin tumors, we designed the following Specific Aims: 1) Determine whether co-expression of incompatible connexins Cx26 and Cx43 inhibits GJIC in keratinocytes; 2) Determine whether co-expression of incompatible connexins Cx26 and Cx43 provides a growth advantage to keratinocytes; 3) Develop transgenic animals deficient in Cx26 expression in epidermis, and Cx26 transgenics with Cx26 targeted to Cx43-positive basal keratinocytes. The results of these experiments will have fundamental importance in deciphering the alternative mechanisms of growth control by connexins.