Dodane V, Kachar B
Laboratory of Cellular Biology, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Rockville, MD 20850, USA.
J Membr Biol. 1996 Feb;149(3):199-209. doi: 10.1007/s002329900020.
Recent evidence suggests that the formation and permeability of tight junctions are actively regulated by second-messenger-generating systems involving G proteins and protein kinase C (PKC). A possible specific target for these regulatory proteins is the tight junction protein ZO-1. An extensive immunocytochemical study was performed in cultured epithelial monolayers of MDCK and Caco-2 cells to identify which isoforms of G proteins and PKC are present at or near zonula occludens complex. Antibodies against alpha-subunits of each one of the four major subfamilies were used for the localization of the G proteins. For the PKC localization, antibodies against eight different isoforms were used. In confluent monolayers, G alpha 12 and PKC zeta, were the only isoforms of these proteins at the cell borders. In subconfluent monolayers, G alpha 12 and PKC zeta were found at the plasma membrane only along the areas of lateral cell-cell contact. These isoforms formed a pattern of distribution very similar to the ZO-1 protein. The present findings indicate that G alpha 12 and PKC zeta may be part of the zonula occludens complex and may locally regulate formation and permeability of tight junctions.
最近有证据表明，紧密连接的形成和通透性受到涉及G蛋白和蛋白激酶C（PKC）的第二信使生成系统的积极调控。这些调节蛋白的一个可能的特定靶点是紧密连接蛋白ZO-1。我们在MDCK和Caco-2细胞的培养上皮单层中进行了广泛的免疫细胞化学研究，以确定在紧密连接复合体处或其附近存在哪些G蛋白和PKC的亚型。针对四个主要亚家族中每一个的α亚基的抗体被用于G蛋白的定位。对于PKC的定位，使用了针对八种不同亚型的抗体。在汇合的单层中，Gα12和PKCζ是这些蛋白在细胞边界处的唯一亚型。在亚汇合的单层中，仅在细胞间侧向接触区域的质膜上发现了Gα12和PKCζ。这些亚型形成的分布模式与ZO-1蛋白非常相似。目前的研究结果表明，Gα12和PKCζ可能是紧密连接复合体的一部分，并可能局部调节紧密连接的形成和通透性。
