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STED超分辨成像研究后高尔基体囊泡介导的TGF-β受体细胞内转运
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摘要
转化生长因子TGF-β信号通路在组织器官发育、细胞增殖、分化、运动和凋亡等过程中扮演重要调节作用。其信号转导相关TGF-β受体在细胞膜上激活、聚集及其内吞转运已有充分的研究,但是对于这些新合成的受体在细胞内的转运及存在状态则知之甚少。在本研究中,我们通过半全内反射荧光成像发现TGF-βⅡ型受体(TβRII)在细胞质中以点状聚集体的形式离散分布,但是TGF-βI型受体(TβRI)未见此现象。通过双色共定位分析发现这些聚集体能够被膜染料染色,并且在TβRII表达后的3-8小时里这些聚集体与后高尔基体囊泡特异性蛋白呈现一定程度的共定位。因此我们推断细胞质中新合成的TβRII聚集体为后高尔基体囊泡,并且19℃低温处理抑制这种囊泡运输实验也进一步验证此结论。但是由于受传统荧光显微镜衍射极限限制,无法直观地观察到TβRII囊泡的结构。因此我们采用受激辐射耗尽(STED)超分辨荧光显微镜对其进一步成像分析。超分辨成像结果证实了TβRII聚集体的环状囊泡结构,并用于研究TβRII在囊泡膜上的分布。这些研究丰富了我们对新合成后的TβRII在细胞内的转运过程的认识。
Transforming growth factor-β(TGF-β) receptors play an important regulatory role in cell proliferation, differentiation, motility, and apoptosis. Although their activation on the cell membrane and internalization from cell membrane to cytoplasm have been well studied, little is known about intracellular trafficking of these receptors. In this work, we found that, unlike TGF-β I receptor(TβRI), the newly synthesized TGF-β II receptor(TβRII) existed as intracellular aggregates and proposed they were post-Golgi vesicles by duel-color quasi-total internal reflection fluorescence microscopy(quasi-TIRFM) imaging. In addition, we visualized the ring-shaped structure of the newly synthesized TβRII-containing vesicles in the cytoplasm by our home-built stimulated emission depletion(STED) microscope. We further investigated the distribution of TβRII on the post-Golgi vesicles. This study offers new information on the intracellular transportation of TGF-β receptors for a better understanding its signaling process.
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