King-Smith C, Basciano P A, Pham N B
Department of Biology, Saint Joseph's University, Philadelphia, Pennsylvania 19131, USA.
Pigment Cell Res. 2001 Feb;14(1):14-22. doi: 10.1034/j.1600-0749.2001.140104.x.
The retinal pigment epithelium (RPE) of teleosts contains pigment granules that migrate in response to changes in light condition. Dissociated, cultured RPE cells in vitro can be triggered to aggregate or disperse pigment granules by the application of cAMP or dopamine, respectively. Previous research using the actin-disrupting drug, cytochalasin D, suggested that pigment granule motility is actin dependent. To further examine the role of actin in pigment granule motility, we tested the effects of the actin-stabilizing drug, jasplakinolide, on pigment granule motility. Pigment granules in previously dispersed RPE cells remained dispersed after jasplakinolide exposure (0.1-1 microM), but the drug halted movement of most pigment granules and stimulated rapid bi-directional movements in a small subset of granules. Jasplakinolide also blocked net pigment granule aggregation and interfered with the maintenance of full aggregation. Although jasplakinolide did not block pigment granule dispersion, it did alter the motility of dispersing granules compared to control cells; rather than the normal saltatory, primarily centrifugal movements, granules of jasplakinolide-treated cells demonstrated slow, creeping centrifugal movements and more rapid bi-directional movements. Jasplakinolide also altered cell morphology; the length and thickness of apical projections increased, and enlarged, paddle-like structures, which contained F-actin appeared at the tips of projections. Actin antibody labeling of jasplakinolide-treated cells revealed a more reticulated network of actin compared to antibody-labeled control cells. These results indicate that jasplakinolide-induced disruption of the actin network compromises normal pigment granule dispersion and aggregation in isolated RPE cells, thus providing further evidence that these movements are actin dependent.
硬骨鱼的视网膜色素上皮（RPE）含有色素颗粒，这些颗粒会根据光照条件的变化而迁移。体外分离培养的RPE细胞分别施加cAMP或多巴胺可触发色素颗粒聚集或分散。先前使用肌动蛋白破坏药物细胞松弛素D的研究表明，色素颗粒的运动依赖于肌动蛋白。为了进一步研究肌动蛋白在色素颗粒运动中的作用，我们测试了肌动蛋白稳定药物茉莉素对色素颗粒运动的影响。在暴露于茉莉素（0.1-1 microM）后，先前分散的RPE细胞中的色素颗粒仍保持分散状态，但该药物使大多数色素颗粒停止运动，并在一小部分颗粒中刺激了快速的双向运动。茉莉素还阻止了色素颗粒的净聚集，并干扰了完全聚集的维持。尽管茉莉素没有阻止色素颗粒的分散，但与对照细胞相比，它确实改变了分散颗粒的运动；茉莉素处理的细胞的颗粒没有正常的跳跃式、主要是离心运动，而是表现出缓慢的、蠕动的离心运动和更快的双向运动。茉莉素还改变了细胞形态；顶端突起的长度和厚度增加，并且在突起的尖端出现了含有F-肌动蛋白的扩大的桨状结构。与抗体标记的对照细胞相比，茉莉素处理的细胞的肌动蛋白抗体标记显示出更网状的肌动蛋白网络。这些结果表明，茉莉素诱导的肌动蛋白网络破坏损害了分离的RPE细胞中正常的色素颗粒分散和聚集，从而提供了进一步的证据表明这些运动依赖于肌动蛋白。
