Blanks J C, Hageman G S, Johnson L V, Spee C
Department of Ophthalmology, University of Southern California School of Medicine, Los Angeles 90033.
J Comp Neurol. 1988 Apr 8;270(2):288-300. doi: 10.1002/cne.902700209.
Glycoconjugates, including glycolipids, glycoproteins, and proteoglycans, are present in the plasma membrane of photoreceptor cells and in the interphotoreceptor matrix surrounding photoreceptor cell ellipsoids and outer segments. Although the precise function of these molecules is unknown, they may be important in mediating photoreceptor-pigment epithelial cell interactions, outer segment membrane assembly, and/or disc shedding. Lectins, affinity ligands for defined carbohydrate sequences, have proven particularly useful in studying the glycoconjugate composition of the interphotoreceptor matrix. The peanut lectin selectively binds to domains of the interphotoreceptor matrix surrounding cone ("cone matrix sheaths"), but not rod inner and outer segments. This is evidence for the existence of chemical and structural heterogeneity within the interphotoreceptor matrix. The studies described herein utilized ultrastructural pre-embedding histochemical labeling to assess whether, in addition to the surrounding interphotoreceptor matrix, peanut lectin binding is associated directly with that plasma membrane of cone inner and outer segments. This study confirms that ferritin-conjugated peanut agglutinin binds to cone matrix sheaths, and, in addition, provides ultrastructural evidence for the presence of binding to the plasma membrane surrounding cone inner and outer segments. The data suggest that cone membrane-associated peanut agglutinin-binding molecules may differ from those located within cone matrix sheaths.
糖缀合物，包括糖脂、糖蛋白和蛋白聚糖，存在于光感受器细胞的质膜以及围绕光感受器细胞椭球体和外段的光感受器间基质中。尽管这些分子的确切功能尚不清楚，但它们可能在介导光感受器 - 色素上皮细胞相互作用、外段膜组装和/或盘膜脱落方面发挥重要作用。凝集素是特定碳水化合物序列的亲和配体，已被证明在研究光感受器间基质的糖缀合物组成方面特别有用。花生凝集素选择性地结合视锥细胞周围的光感受器间基质区域（“视锥细胞基质鞘”），但不结合视杆细胞的内段和外段。这证明了光感受器间基质内存在化学和结构异质性。本文所述的研究利用超微结构预包埋组织化学标记来评估除了周围的光感受器间基质外，花生凝集素结合是否直接与视锥细胞内段和外段的质膜相关。这项研究证实了铁蛋白偶联的花生凝集素与视锥细胞基质鞘结合，此外，还提供了花生凝集素与视锥细胞内段和外段周围质膜结合的超微结构证据。数据表明，与视锥细胞膜相关的花生凝集素结合分子可能与位于视锥细胞基质鞘内的分子不同。
