Koenig C S, Dabiké M, Bronfman M
Departmento de Biolgia Celular, Universidad Católica de Chile, Santiago.
J Cell Biol. 1987 Dec;105(6 Pt 2):2945-58. doi: 10.1083/jcb.105.6.2945.
Vertebrate oxyntic cells, responsible for gastric HCl production, undergo a remarkable morphological reorganization in relation to their secretory cycle. In resting state, the luminal surface of the cells is smooth; a peculiar system of endocellular membranes, the tubular system, occupies the luminal cytoplasm. Actin filaments frame a cortical network between the tubular system and the luminal plasma membrane. With the onset of HCl secretion, the tubular system becomes incorporated into the luminal plasma membrane. Villous processes containing microfilaments fill the secretory surface. This morphological reorganization of membranes and cytoskeletal matrix could regulate HCl secretion by translocation of membranes containing the proton pump from the endocellular compartment to the secretory surface. In this paper, we describe the isolation of membranes that selectively belong to the tubular system or to the cytoplasmic processes of the secretory surface of chicken oxyntic cells. Chicken oxyntic cells are the main cellular component of the proventricular glands. A resting state was obtained after cimetidine treatment, whereas the HCl-secretory state was induced by histamine. We present a comparative analysis of resting and stimulated chicken gastric glands by quantitative subcellular fractionation. The HCl secretory state was related to specific modifications in membrane fractions derived from the secretory pole of oxyntic cells. Morphological and functional reorganization of oxyntic cells was closely correlated with changes in: the sedimentation pattern of the marker enzyme of the apical pole membrane (K-NPPase), the total activity of K-NPPase and nonmitochondrial Mg-ATPase, the valinomycin dependence of K-ATPase, and polypeptides that cosediment in purified membrane fractions. Changes in the distribution pattern of K-NPPase after fractionation of histamine-stimulated glands were consistent with the replacement of the small vesicles typical of resting glands by dense membrane profiles, analogous to the luminal processes of stimulated oxyntic cells. SDS-PAGE showed that, in purified membrane fractions of stimulated glands, the concentration of 28-, 43-, and 200-kD polypeptides increased while that of 95- and 250-kD polypeptides decreased. The present results define the tubular system of oxyntic cells as an organelle with properties different from those of endoplasmic reticulum, mitochondria, and plasma membrane. The biochemical and physico-chemical properties of this membraneous system changed when the organization of the membranes and the cytoskeletal matrix of the apical pole was modified by the onset of HCl secretion.
负责胃盐酸分泌的脊椎动物壁细胞，在其分泌周期中会经历显著的形态重组。在静息状态下，细胞的管腔表面光滑；一种特殊的细胞内膜系统，即管状系统，占据管腔细胞质。肌动蛋白丝在管状系统和管腔质膜之间构成一个皮质网络。随着盐酸分泌的开始，管状系统并入管腔质膜。含有微丝的绒毛状突起布满分泌表面。这种膜和细胞骨架基质的形态重组可能通过将含有质子泵的膜从细胞内区室转运到分泌表面来调节盐酸分泌。在本文中，我们描述了选择性属于鸡壁细胞管状系统或分泌表面细胞质突起的膜的分离。鸡壁细胞是腺胃腺的主要细胞成分。西咪替丁处理后获得静息状态，而组胺诱导盐酸分泌状态。我们通过定量亚细胞分级分离对静息和刺激的鸡胃腺进行了比较分析。盐酸分泌状态与源自壁细胞分泌极的膜组分的特定修饰有关。壁细胞的形态和功能重组与以下变化密切相关：顶端极膜标记酶（K-NPPase）的沉降模式、K-NPPase和非线粒体Mg-ATPase的总活性、K-ATPase对缬氨霉素的依赖性以及在纯化膜组分中共沉降的多肽。组胺刺激的腺体分级分离后K-NPPase分布模式的变化与静息腺体典型的小泡被致密膜轮廓取代一致，类似于刺激的壁细胞的管腔突起。SDS-PAGE显示，在刺激腺体的纯化膜组分中，28-kD、43-kD和200-kD多肽的浓度增加，而95-kD和250-kD多肽的浓度降低。目前的结果将壁细胞的管状系统定义为一种细胞器，其性质不同于内质网、线粒体和质膜。当顶端极的膜和细胞骨架基质的组织因盐酸分泌的开始而改变时，这个膜系统的生化和物理化学性质也会发生变化。
