Celica Biomedical Center, Ljubljana, Slovenia.
Glia. 2010 Aug;58(10):1208-19. doi: 10.1002/glia.21000.
Intermediate filament (IF) proteins upregulation is a hallmark of astrocyte activation and reactive gliosis, but its pathophysiological implications remain incompletely understood. A recently reported association between IFs and directional mobility of peptidergic vesicles allows us to hypothesize that IFs affect vesicle dynamics and exocytosis-mediated astrocyte communication with neighboring cells. Here, we ask whether the trafficking of recycling vesicles (i.e., those fused to and then retrieved from the plasma membrane) and endosomes/lysosomes depends on IFs. Recycling vesicles were labeled by antibodies against vesicle glutamate transporter 1 (VGLUT1) and atrial natriuretic peptide (ANP), respectively, and by lysotracker, which labels endosomes/lysosomes. Quantitative fluorescence microscopy was used to monitor the mobility of labeled vesicles in astrocytes, derived from either wild-type (WT) mice or mice deficient in glial fibrillary acidic protein and vimentin (GFAP(-/-)Vim(-/-)), the latter lacking astrocyte IFs. Stimulation with ionomycin or ATP enhanced the mobility of VGLUT1-positive vesicles and reduced the mobility of ANP-positive vesicles in WT astrocytes. In GFAP(-/-)Vim(-/-) astrocytes, both vesicle types responded to stimulation, but the relative increase in mobility of VGLUT1-positive vesicles was more prominent compared with nonstimulated cells, whereas the stimulation-dependent attenuation of ANP-positive vesicles mobility was reduced compared with nonstimulated cells. The mobility of endosomes/lysosomes decreased following stimulation in WT astrocytes. However, in GFAP(-/-)Vim(-/-) astrocytes, a small increase in the mobility of endosomes/lysosomes was observed. These findings show that astrocyte IFs differentially affect the stimulation-dependent mobility of vesicles. We propose that upregulation of IFs in pathologic states may alter the function of astrocytes by deregulating vesicle trafficking.
中间丝（IF）蛋白的上调是星形胶质细胞激活和反应性神经胶质增生的标志，但它的病理生理意义仍不完全清楚。最近有报道称 IF 与肽囊泡的定向迁移有关，这使我们可以假设 IF 影响囊泡动力学和细胞外排介导的星形胶质细胞与邻近细胞的通讯。在这里，我们询问回收囊泡（即与质膜融合然后从质膜中回收的囊泡）和内体/溶酶体的运输是否依赖于 IF。回收囊泡通过针对囊泡谷氨酸转运蛋白 1（VGLUT1）和心钠肽（ANP）的抗体以及标记内体/溶酶体的 lysotracker 进行标记。定量荧光显微镜用于监测来自野生型（WT）小鼠或缺乏胶质纤维酸性蛋白和波形蛋白（GFAP（-/-）Vim（-/-））的星形胶质细胞中标记囊泡的流动性，后者缺乏星形胶质细胞 IF。离子霉素或 ATP 刺激增强了 WT 星形胶质细胞中 VGLUT1 阳性囊泡的流动性，并降低了 ANP 阳性囊泡的流动性。在 GFAP（-/-）Vim（-/-）星形胶质细胞中，两种囊泡类型都对刺激做出反应，但与非刺激细胞相比，VGLUT1 阳性囊泡的流动性增加更为明显，而与非刺激细胞相比，刺激依赖性的 ANP 阳性囊泡流动性减弱。WT 星形胶质细胞刺激后内体/溶酶体的流动性降低。然而，在 GFAP（-/-）Vim（-/-）星形胶质细胞中，观察到内体/溶酶体的流动性略有增加。这些发现表明星形胶质细胞 IF 不同地影响刺激依赖性囊泡的流动性。我们提出，病理状态下 IF 的上调可能通过改变囊泡运输来改变星形胶质细胞的功能。
