MEMBRANE ASSEMBLY IN RETINAL PHOTORECEPTORS .1. FREEZE-FRACTURE ANALYSIS OF CYTOPLASMIC VESICLES IN RELATIONSHIP TO DISK ASSEMBLY
MEMBRANE ASSEMBLY IN RETINAL PHOTORECEPTORS .1. FREEZE-FRACTURE ANALYSIS OF CYTOPLASMIC VESICLES IN RELATIONSHIP TO DISK ASSEMBLY
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DOI：
10.1083/jcb.87.2.451
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发表时间：
1980-01-01
影响因子：
7.8
通讯作者：
PFENNINGER, KH
中科院分区：
文献类型：
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作者：
BESHARSE, JC;PFENNINGER, KH
通过比较冷冻断裂的光感受器内外段不同膜室中膜内颗粒（IMP）的密度和大小分布，研究了光感受器内段细胞质膜和不断更新的外盘膜之间的前体产物关系。非洲爪蟾的杆和锥外节的特征在于一个相对均匀的分布。4400-4700 IMP/μ m2，在盘膜的P[原生质]面（PF）小叶中。IMP在外段质膜、睫状体质膜和紧邻睫状体周围区域内段质膜中的分布相似。在每种情况下，IMP的尺寸分布表征为单峰，平均直径为λ。10 nm。内质网的PF小叶、高尔基复合体和纤毛附近的小泡具有IMP，其大小分布与纤毛和外节中的大小分布相似，但平均密度为约。2000/μ m2。IMP的平均尺寸较小（约7.5内节质膜的PF小叶（不包括纤毛周区）中有10个（nm）。IMP在纤毛内节细胞质膜和外节细胞质膜中的大小分布相似，表明这两个系统之间存在着一种代谢产物-产物关系。富含囊泡的纤毛周围区域的结构和IMP在该区域中具有不同尺寸分布的分离意味着用于掺入外段的组分以预先形成的膜包装（囊泡）的形式存在，其与纤毛周围区域中的内段质膜融合。随后，膜组分可经由睫状质膜转移至外节的成形盘。
Precursor-product relationships between cytoplasmic membranes of the inner segment of photoreceptors and the continually renewed outer disc membrane were studied by comparing the density and size distribution of intramembrane particles (IMP) in various membrane compartments of freeze-fractured photoreceptor inner and outer segments. Rod and cone outer segments of Xenopus laevis were characterized by a relatively uniform distribution of .apprx. 4400-4700 IMP/.mu.m2 in P[protoplasmic]-face (PF) leaflets of disc membranes. A similar distribution of IMP was found in the outer segment plasma membrane, the ciliary plasma membrane and in the plasma membrane of the inner segment in the immediate periciliary region. In each case the size distribution of IMP was characterized as unimodal with a mean diameter of .apprx. 10 nm. PF leaflets of endoplasmic reticulum, Golgi complex and vesicles near the cilium had IMP with a size distribution similar to that in the cilium and outer segment, but with an average density of .apprx. 2000/.mu.m2. IMP were smaller in average size (.apprx. 7.5 nm) in PF leaflets of inner segment plasma membrane, exclusive of the periciliary region. The similarity of size distribution of IMP in inner segment cytoplasmic membranes and those within the plasmalemma of the cilium and outer segment suggest a precursor-product relationship between the 2 systems. The structure of the vesicle-rich periciliary region and the segregation of IMP with different size distributions in this region imply that components destined for incorporation into the outer segment exist as preformed membrane packages (vesicles) which fuse with the inner segment plasma membrane in the periciliary region. Subsequently, membrane components may be transferred to forming discs of the outer segment via the ciliary plasma membrane.