Gillard B K, Thurmon L T, Marcus D M
Department of Medicine, Baylor College of Medicine, Houston, Texas 77030.
Cell Motil Cytoskeleton. 1992;21(4):255-71. doi: 10.1002/cm.970210402.
We reported recently that two glycosphingolipids (GSLs), globoside (Gb4) and ganglioside GM3, colocalized with vimentin intermediate filaments of human umbilical vein endothelial cells. To determine whether this association is unique to endothelial cells or to vimentin, we analyzed a variety of cell types. Double-label immunofluorescent staining of fixed, permeabilized cells, with and without colcemid treatment, was performed with antibodies against glycolipids and intermediate filaments. Globoside colocalized with vimentin in human and mouse fibroblasts, with desmin in smooth muscle cells, with keratin in keratinocytes and hepatoma cells, and with glial fibrillary acidic protein (GFAP) in glial cells. Globoside colocalization was detected only with vimentin in MDCK and HeLa cells, which contain separate vimentin and keratin networks. GM3 ganglioside also colocalized with vimentin in human fibroblasts. Association of other GSLs with intermediate filaments was not detected by immunofluorescence, but all cell GSLs were detected in cytoskeletal fractions of metabolically labelled endothelial cells. These observations indicate that globoside colocalizes with vimentin, desmin, kertain and GFAP, with a preference for vimentin in cells that contain both vimentin and keratin networks. The nature of the association is not yet known. Globoside and GM3 may be present in vesicles associated with intermediate filaments (IF), or bound directly to IF or IF associated proteins. The prevalence of this association suggests that colocalization of globoside with the intermediate filament network has functional significance. We are investigating the possibility that intermediate filaments participate in the intracellular transport and sorting of glycosphingolipids.
我们最近报道，两种糖鞘脂（GSLs），红细胞糖苷脂（Gb4）和神经节苷脂GM3，与人脐静脉内皮细胞的波形蛋白中间丝共定位。为了确定这种关联是内皮细胞或波形蛋白所特有的，我们分析了多种细胞类型。使用抗糖脂和中间丝的抗体，对固定、通透处理的细胞进行双标记免疫荧光染色，有无秋水仙酰胺处理均可。红细胞糖苷脂在人及小鼠成纤维细胞中与波形蛋白共定位，在平滑肌细胞中与结蛋白共定位，在角质形成细胞和肝癌细胞中与角蛋白共定位，在神经胶质细胞中与胶质纤维酸性蛋白（GFAP）共定位。仅在含有独立波形蛋白和角蛋白网络的MDCK和HeLa细胞中，检测到红细胞糖苷脂与波形蛋白共定位。神经节苷脂GM3在人成纤维细胞中也与波形蛋白共定位。免疫荧光未检测到其他GSLs与中间丝的关联，但在代谢标记的内皮细胞的细胞骨架组分中检测到了所有细胞的GSLs。这些观察结果表明，红细胞糖苷脂与波形蛋白、结蛋白、角蛋白和GFAP共定位，在同时含有波形蛋白和角蛋白网络的细胞中更倾向于与波形蛋白共定位。这种关联的性质尚不清楚。红细胞糖苷脂和GM3可能存在于与中间丝（IF）相关的囊泡中，或直接与IF或IF相关蛋白结合。这种关联的普遍性表明，红细胞糖苷脂与中间丝网络的共定位具有功能意义。我们正在研究中间丝参与糖鞘脂细胞内运输和分选的可能性。
