Drenckhahn D, Wagner H J
Eur J Cell Biol. 1985 May;37:156-68.
Photoreceptors of many nonmammalian vertebrate species display pronounced light-dependent movements which are absent in mammalian species. In order to further analyze the molecular basis of receptor movements and of simultaneous migration of melanin granules in pigment epithelial processes, we investigated the distribution of actin, myosin and the actin-binding muscular proteins alpha-actinin and vinculin in the retina of various vertebrate species. The species investigated can be divided in two groups (i) those possessing retinomotor capacity (fish, frog, turtle, chick) and (ii) those in which retinomotor activities are negligible or absent (gecko, mouse, rat). Prominent bundles of actin filaments extending throughout the long axis of photoreceptor inner segments were only found in species possessing retinomotor capacity, while comparable actin filament bundles were absent or poorly developed in photoreceptors of species lacking significant retinomotor capacity. In all species examined, a well developed circumferential band of actin filaments was associated with the zonula adhaerens-like junctions between photoreceptors and Müller (glial) cells forming the external limiting membrane. This area was also identified as the exclusive site of myosin, alpha-actinin and vinculin (only in the chick, alpha-actinin-like immunoreactivity was also found along the photoreceptor actin filament bundles). Thus, the external limiting membrane may be important for both structural support and for providing a possible site of filament sliding for photoreceptor movements. In pigment epithelium actin, myosin, alpha-actinin and vinculin were concentrated circumferentially in the area of the terminal bar which has been previously shown to be contractile. In all species apical pigment-epithelial processes displayed actin-like fluorescence of varying intensities. Another site of actin-like staining were photoreceptor synaptic complexes which represent a well known site for synaptic plasticity. Immunoblotting studies on the avascular chick retina revealed polypeptide bands at Mr approximately 130 000, approximately 100 000, and 42 000 which were specific for vinculin, alpha-actinin and actin, respectively. A faint polypeptide band comigrating with thymus myosin heavy chain indicates myosin to be only a minor component of the retina (chick and fish).
许多非哺乳类脊椎动物物种的光感受器表现出明显的光依赖性运动，而哺乳类物种则没有这种运动。为了进一步分析受体运动以及色素上皮突起中黑色素颗粒同时迁移的分子基础，我们研究了肌动蛋白、肌球蛋白以及肌动蛋白结合肌肉蛋白α - 辅肌动蛋白和纽蛋白在各种脊椎动物物种视网膜中的分布。所研究的物种可分为两组：（i）具有视网膜运动能力的物种（鱼类、青蛙、乌龟、小鸡），以及（ii）视网膜运动活动可忽略不计或不存在的物种（壁虎、小鼠、大鼠）。仅在具有视网膜运动能力的物种中发现了沿光感受器内段长轴延伸的显著肌动蛋白丝束，而在缺乏显著视网膜运动能力的物种的光感受器中，类似的肌动蛋白丝束不存在或发育不良。在所有检查的物种中，一条发育良好的肌动蛋白丝周带与光感受器和形成外界膜的米勒（神经胶质）细胞之间的黏着小带样连接相关。该区域也被确定为肌球蛋白、α - 辅肌动蛋白和纽蛋白的唯一存在部位（仅在小鸡中，沿光感受器肌动蛋白丝束也发现了α - 辅肌动蛋白样免疫反应性）。因此，外界膜对于结构支持以及为光感受器运动提供细丝滑动的可能位点可能都很重要。在色素上皮中，肌动蛋白、肌球蛋白、α - 辅肌动蛋白和纽蛋白周向集中在先前已证明具有收缩性的终棒区域。在所有物种中，顶端色素上皮突起显示出强度不同的肌动蛋白样荧光。另一个肌动蛋白样染色部位是光感受器突触复合体，这是一个众所周知的突触可塑性部位。对无血管小鸡视网膜的免疫印迹研究显示，分别针对纽蛋白、α - 辅肌动蛋白和肌动蛋白的多肽条带在Mr约为130000、约100000和42000处。一条与胸腺肌球蛋白重链共迁移的微弱多肽条带表明肌球蛋白只是视网膜（小鸡和鱼类）的次要成分。
