Albertini D F, Anderson E
J Cell Biol. 1977 Apr;73(1):111-27. doi: 10.1083/jcb.73.1.111.
Thin-section electron microscope analysis of rat and rabbit-cultured granulosa cells treated with concanavalin A (Con A) at 37 degrees C revealed coordinated changes in the cytoplasmic disposition of microfilaments, thick filaments, and microtubules during cap formation and internalization of lectin-receptor complexes. Con A-receptor clustering is accompanied by an accumulation of subplasmalemmal microfilaments which assemble into a loosely woven ring as patches of receptor move centrally on the cell surface. Periodic densities appear in the microfilament ring which becomes reduced in diameter as patches coalesce to form a single central cap. Microtubules and thick filaments emerge associated with the capped membrane. Capping is followed by endocytosis of the con A-receptor complexes. During this process, the microfilament ring is displaced basally into the cytoplasm and endocytic vesicles are transported to the paranuclear Golgi complex along microtubules and thick filaments. Eventually, these vesicles aggregate near the cell center where they are embedded in a dense meshwork of thick filaments. Freeze-fracture analysis of Con A-capped granulosa cells revealed no alteration in the arrangement of peripheral intramembrane particles but large, smooth domains were conspicuous in the capped region of the plasma membrane. The data are discussed with reference to the participation of microtubules and microfilaments in the capping process.
对在37摄氏度下用伴刀豆球蛋白A（Con A）处理的大鼠和兔培养颗粒细胞进行的超薄切片电子显微镜分析显示，在凝集素受体复合物的帽形成和内化过程中，微丝、粗丝和微管的细胞质分布发生了协同变化。Con A受体聚集伴随着质膜下微丝的积累，随着受体斑块在细胞表面向中心移动，微丝组装成一个松散编织的环。微丝环中出现周期性密度，随着斑块合并形成单个中央帽，微丝环直径减小。微管和粗丝与帽状膜相关出现。帽形成后，Con A受体复合物发生内吞作用。在此过程中，微丝环向基部移入细胞质，内吞小泡沿着微管和粗丝被运输到核旁高尔基体复合物。最终，这些小泡在细胞中心附近聚集，它们被嵌入粗丝的致密网络中。对Con A帽状颗粒细胞的冷冻断裂分析显示，外周膜内颗粒的排列没有改变，但在质膜的帽状区域有明显的大的光滑结构域。结合微管和微丝在帽形成过程中的参与对数据进行了讨论。
