Walker G R, Taylor J D, Tchen T T
Department of Chemistry, Wayne State University, Detroit, MI 48202.
Cell Motil Cytoskeleton. 1989;14(4):458-68. doi: 10.1002/cm.970140404.
Immunofluorescence and phase-contrast microscopic studies of goldfish xanthophores with aggregated or dispersed pigment show two unusual features. First, immunofluorescence studies with anti-actin show punctate structures instead of filaments. These punctate structures are unique for the xanthophores and are absent from both goldfish dermal non-pigment cells and a dedifferentiated cell line (GEM-81) derived from a goldfish xanthophore tumor. Comparison of immunofluorescence and phase-contrast microscopic images with electron microscopic images of thin sections and of Triton-insoluble cytoskeletons show that these punctate structures represent pterinosomes with radiating F-actin. The high local concentration of actin around the pterinosomes results in strong localized fluorescence such that, when the images have proper brightness for these structures, individual actin filaments elsewhere in the cell are too weak in their fluorescence to be visible in the micrographs. Second, whereas immunofluorescence images with anti-tubulin show typical patterns in xanthophores with either aggregated or dispersed pigment, namely, filaments radiating out from the microtubule organizing center, immunofluorescence images with anti-actin or with anti-intermediate filament proteins show different patterns in xanthophores with aggregated versus dispersed pigment. In cells with dispersed pigment, the punctate structures seen with anti-actin are relatively evenly distributed in the cytoplasm, and intermediate filaments appear usually as a dense perinuclear band and long filaments elsewhere in the cytoplasm. In cells with aggregated pigment, both intermediate filaments and pterinosomes with associated actin are largely excluded from the space occupied by the pigment aggregate, and the band of intermediate filaments surrounds not only the nucleus but also the pigment aggregate. The patterns of distribution of the different cytoskeleton components, together with previous results from this laboratory, indicate that formation of the pigment aggregate depends at least in part on the interaction between pigment organelles and microtubules. The possibility that intermediate filaments may play a role in the formation/stabilization of the pigment aggregate is discussed.
对具有聚集或分散色素的金鱼黄色素细胞进行免疫荧光和相差显微镜研究，发现了两个不同寻常的特征。首先，用抗肌动蛋白进行免疫荧光研究显示出点状结构而非丝状结构。这些点状结构是黄色素细胞所特有的，在金鱼皮肤非色素细胞以及源自金鱼黄色素细胞瘤的去分化细胞系（GEM - 81）中均不存在。将免疫荧光和相差显微镜图像与薄切片的电子显微镜图像以及 Triton 不溶性细胞骨架进行比较，结果表明这些点状结构代表带有放射状 F - 肌动蛋白的蝶呤体。蝶呤体周围肌动蛋白的高局部浓度导致强烈的局部荧光，以至于当图像对于这些结构具有适当亮度时，细胞中其他位置的单个肌动蛋白丝的荧光太弱，在显微照片中无法看到。其次，虽然用抗微管蛋白的免疫荧光图像在具有聚集或分散色素的黄色素细胞中显示出典型模式，即从微管组织中心放射出的丝状结构，但用抗肌动蛋白或抗中间丝蛋白的免疫荧光图像在具有聚集色素与分散色素的黄色素细胞中显示出不同模式。在具有分散色素的细胞中，用抗肌动蛋白观察到的点状结构相对均匀地分布在细胞质中，中间丝通常表现为致密的核周带以及细胞质中其他位置的长丝。在具有聚集色素的细胞中，中间丝和带有相关肌动蛋白的蝶呤体在很大程度上被排除在色素聚集体占据的空间之外，中间丝带不仅围绕细胞核，还围绕色素聚集体。不同细胞骨架成分的分布模式，连同本实验室先前的结果，表明色素聚集体的形成至少部分取决于色素细胞器与微管之间的相互作用。文中还讨论了中间丝可能在色素聚集体的形成/稳定中发挥作用的可能性。
