Drenckhahn D, Dermietzel R
Department of Anatomy and Cell Biology, University of Marburg, Federal Republic of Germany.
J Cell Biol. 1988 Sep;107(3):1037-48. doi: 10.1083/jcb.107.3.1037.
In the present study we have used immunogold labeling of ultrathin sections of the intact chicken and human intestinal epithelium to obtain further insight into the molecular structure of the brush-border cytoskeleton. Actin, villin, and fimbrin were found within the entire microvillus filament bundle, from the tip to the basal end of the rootlets, but were virtually absent from the space between the rootlets. This suggests that the bulk of actin in the brush border is kept in a polymerized and cross-linked state and that horizontally deployed actin filaments are virtually absent. About 70% of the label specific for the 110-kD protein that links the microvillus core bundle to the lipid bilayer was found overlying the microvilli. The remaining label was associated with rootlets and the interrootlet space, where some label was regularly observed in association with vesicles. Since the terminal web did not contain any significant amounts of tubulin and microtubules, the present findings would support a recently proposed hypothesis that the 110-kD protein (which displays properties of an actin-activated, myosin-like ATPase) might also be involved in the transport of vesicles through the terminal web. Label specific for myosin and alpha-actinin was confined to the interrootlet space and was absent from the rootlets. About 10-15% of the myosin label and 70-80% of the alpha-actinin label was observed within the circumferential band of actin filaments at the zonula adherens, where myosin and alpha-actinin displayed a clustered, interrupted pattern that resembles the spacing of these proteins observed in other contractile systems. This circular filament ring did not contain villin, fimbrin, or the 110-kD protein. Finally, actin-specific label was observed in close association with the cytoplasmic aspect of the zonula occludens, suggesting that tight junctions are structurally connected to the microfilament system.
在本研究中，我们对完整的鸡和人肠道上皮超薄切片进行免疫金标记，以进一步深入了解刷状缘细胞骨架的分子结构。在整个微绒毛丝束中，从微绒毛顶端到根的基部末端都发现了肌动蛋白、绒毛蛋白和丝束蛋白，但在根之间的间隙中几乎没有。这表明刷状缘中的大部分肌动蛋白保持聚合和交联状态，并且几乎没有水平排列的肌动蛋白丝。与将微绒毛核心束连接到脂质双层的110-kD蛋白特异性结合的标记，约70%位于微绒毛上方。其余标记与根和根间间隙相关，在根间间隙中经常观察到一些标记与囊泡相关。由于终末网不含任何大量的微管蛋白和微管，目前的研究结果将支持最近提出的一个假设，即110-kD蛋白（显示出肌动蛋白激活的、肌球蛋白样ATP酶的特性）也可能参与囊泡通过终末网的运输。肌球蛋白和α-辅肌动蛋白的特异性标记局限于根间间隙，根中没有。在紧密连接的肌动蛋白丝周带内观察到约10-15%的肌球蛋白标记和70-80%的α-辅肌动蛋白标记，在那里肌球蛋白和α-辅肌动蛋白呈现出聚集、间断的模式，类似于在其他收缩系统中观察到的这些蛋白质的间距。这个环形丝环不含绒毛蛋白、丝束蛋白或110-kD蛋白。最后，观察到肌动蛋白特异性标记与紧密连接的细胞质面紧密相关，表明紧密连接在结构上与微丝系统相连。
