Reidel Boris, Goldmann Tobias, Giessl Andreas, Wolfrum Uwe
Department of Cell and Matrix Biology, Institute of Zoology, Johannes Gutenberg University of Mainz, Germany.
Cell Motil Cytoskeleton. 2008 Oct;65(10):785-800. doi: 10.1002/cm.20300.
In vertebrate rod photoreceptor cells, arrestin and the visual G-protein transducin move between the inner segment and outer segment in response to changes in light. This stimulus dependent translocation of signalling molecules is assumed to participate in long term light adaptation of photoreceptors. So far the cellular basis for the transport mechanisms underlying these intracellular movements remains largely elusive. Here we investigated the dependency of these movements on actin filaments and the microtubule cytoskeleton of photoreceptor cells. Co-cultures of mouse retina and retinal pigment epithelium were incubated with drugs stabilizing and destabilizing the cytoskeleton. The actin and microtubule cytoskeleton and the light dependent distribution of signaling molecules were subsequently analyzed by light and electron microscopy. The application of cytoskeletal drugs differentially affected the cytoskeleton in photoreceptor compartments. During dark adaptation the depolymerization of microtubules as well as actin filaments disrupted the translocation of arrestin and transducin in rod photoreceptor cells. During light adaptation only the delivery of arrestin within the outer segment was impaired after destabilization of microtubules. Movements of transducin and arrestin required intact cytoskeletal elements in dark adapting cells. However, diffusion might be sufficient for the fast molecular movements observed as cells adapt to light. These findings indicate that different molecular translocation mechanisms are responsible for the dark and light associated translocations of arrestin and transducin in rod photoreceptor cells.
在脊椎动物视杆光感受器细胞中，抑制蛋白和视觉G蛋白转导素会根据光的变化在内段和外段之间移动。这种信号分子的刺激依赖性易位被认为参与了光感受器的长期光适应过程。到目前为止，这些细胞内运动背后的运输机制的细胞基础仍然很大程度上不清楚。在这里，我们研究了这些运动对光感受器细胞的肌动蛋白丝和微管细胞骨架的依赖性。将小鼠视网膜和视网膜色素上皮的共培养物与稳定和破坏细胞骨架的药物一起孵育。随后通过光学显微镜和电子显微镜分析肌动蛋白和微管细胞骨架以及信号分子的光依赖性分布。细胞骨架药物的应用对光感受器区室中的细胞骨架有不同的影响。在暗适应期间，微管以及肌动蛋白丝的解聚破坏了视杆光感受器细胞中抑制蛋白和转导素的易位。在光适应期间，微管不稳定后仅外段内抑制蛋白的递送受损。在暗适应细胞中，转导素和抑制蛋白的移动需要完整的细胞骨架成分。然而，对于细胞适应光时观察到的快速分子运动，扩散可能就足够了。这些发现表明，不同的分子易位机制负责视杆光感受器细胞中抑制蛋白和转导素与暗和光相关的易位。
