Weiner O H, Murphy J, Griffiths G, Schleicher M, Noegel A A
Max-Planck-Institut für Biochemie, Martinsried, F.R.G.
J Cell Biol. 1993 Oct;123(1):23-34. doi: 10.1083/jcb.123.1.23.
Comitin (p24) was first identified in Dictyostelium discoideum as a membrane-associated protein which binds in gel overlay assays to G and F actin. To analyze its actin-binding properties we used purified, bacterially expressed comitin and found that it binds to F actin in spin down experiments and increases the viscosity of F actin solutions even under high-salt conditions. Immunofluorescence studies, cell fractionation experiments and EM studies of vesicles precipitated with comitin-specific monoclonal antibodies showed that comitin was present in D. discoideum on: (a) a perinuclear structure with tubular or fibrillary extensions; and (b) on vesicles distributed throughout the cell. In immunofluorescence experiments using comitin antibodies NIH 3T3 fibroblasts showed a similar staining pattern as D. discoideum cells. Using bona fide Golgi markers the perinuclear structure was identified as the Golgi apparatus. The results were supported by an electron microscopic study using cryosections. Based on these data we propose that also in Dictyostelium the stained perinuclear structure is the Golgi apparatus. In vivo the perinuclear structure was found to be attached to the actin and the microtubule network. Alteration of the actin network or depolymerization of the microtubules led to its dispersal into vesicles distributed throughout the cell. These results suggest that the Golgi apparatus in D. discoideum is connected to the actin network by comitin. This protein seems also to be present in mammalian cells.
Comitin（p24）最初是在盘基网柄菌中被鉴定为一种膜相关蛋白，它在凝胶覆盖试验中与G肌动蛋白和F肌动蛋白结合。为了分析其肌动蛋白结合特性，我们使用了纯化的、细菌表达的Comitin，发现在沉降实验中它与F肌动蛋白结合，并且即使在高盐条件下也能增加F肌动蛋白溶液的粘度。用Comitin特异性单克隆抗体沉淀囊泡的免疫荧光研究、细胞分级分离实验和电子显微镜研究表明，Comitin存在于盘基网柄菌的以下部位：（a）具有管状或纤维状延伸的核周结构上；（b）分布于整个细胞的囊泡上。在使用Comitin抗体的免疫荧光实验中，NIH 3T3成纤维细胞显示出与盘基网柄菌细胞相似的染色模式。使用真正的高尔基体标记物，核周结构被鉴定为高尔基体。这些结果得到了使用冷冻切片的电子显微镜研究的支持。基于这些数据，我们提出在盘基网柄菌中，染色的核周结构也是高尔基体。在体内，发现核周结构附着于肌动蛋白和微管网络。肌动蛋白网络的改变或微管的解聚导致其分散成分布于整个细胞的囊泡。这些结果表明，盘基网柄菌中的高尔基体通过Comitin与肌动蛋白网络相连。这种蛋白质似乎也存在于哺乳动物细胞中。
