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【bio-news】细胞内运输的分子机制
Molecular mechanism provides intra-cellular traffic signal
City planners could learn a lesson or two from tiny cells on how to maximize traffic flow.
Researchers at the University of Illinois at Chicago have found that intra-cellular trafficking is tightly coordinated for maximum flow through cellular compartments -- much as vehicles on a crowded road are allowed to pass quickly through a succession of green traffic lights.
The molecular mechanism that underlies this coordination is reported by lead researcher Nava Segev, UIC professor of biological sciences, in the November issue of Nature Cell Biology.
While the finding was made using yeast cells, intra-cellular mechanisms discovered in yeast almost invariably correspond to processes in mammalian cells, including humans, and the mechanism Segev described may find applicability in the biomedical field.
"Every system in our body depends on intra-cellular trafficking, because anything that goes from the inside of a cell to the outside, or from outside to inside, uses this process," Segev said. "Malfunctioning of this pathway can cause a variety of human diseases. For example, problems in insulin secretion or presentation of insulin-receptors on the cell membrane result in diabetes. Defects in growth factor secretion and presentation of their receptors on cells result in cancer. Defects in neurotransmitter release or internalization result in brain disorders."
A special set of proteins is responsible for the coordination. Molecular switches that go by the letters Ypt allow membrane-enclosed vesicles to pass in and out of cellular compartments. Activator proteins flip the switches on. One activator protein, called TRAPP, coordinates two Ypt switches for quick entrance and subsequent exit from a central cellular compartment known as the Golgi apparatus.
"The Golgi is a central station in all cells, through which all intra-cellular traffic passes," Segev explained.
Specific subunits of TRAPP previously identified by the UIC researchers were found to be the key to coordinated switching and traffic flow through the Golgi. They have now shown that components of TRAPP act in sequence to direct the flow. One form of TRAPP turns on the first Ypt for entry into the Golgi, while at the other end of the Golgi, two subunits join TRAPP to activate the Ypt required for exit from the Golgi, Segev said.
Segev said the mechanism that her lab identified must now be shown to exist in mammalian cells. Her earlier discovery of the Ypt molecular switches in yeast and the subsequent finding of their homologues in mammalian cells, together with the fact that TRAPP is conserved in evolution from yeast to man, lead her to believe the entire coordinated switching mechanism is universal. 认领此篇 分子装置成为细胞内运输的信号灯
城市规划者们应该向微小的细胞学习如何使城市交通达到最大的流量。
芝加哥的伊利诺斯州立大学的研究者们发现细胞内部的各个细胞器之间保持着最大限度的运输，就像是在拥挤的街道上车辆快速的通过一系列的绿色信号灯一样。
伊利诺斯州立大学的生物学家、首席研究员Nava Segev教授在十一月的《自然细胞生物学》期刊中报道指出这种协调运输的方式是有其分子机制的。
尽管此发现是在酵母细胞进行的，但是在酵母细胞中发现的这种分子机制 都能够相对应的在哺乳动物细胞中找到，包括人的细胞，Segev所描绘的分子机制可能也适用于医学生物学领域。
“我们身体的每一个系统都依靠于细胞内的运输，因为任何东西都是依靠运输从细胞内部运送到细胞外部，或者从外部运送到内部”。Segev说，“在人体中这种途径如果出现问题就会引起各种疾病。例如，胰岛素的分泌或细胞膜上的胰岛素受体出现问题就会引起糖尿病。生长因子的分泌和细胞上的生长因子受体出现问题就会引发癌症。神经递质的释放出现问题或内在的一些原因就会导致神经混乱。”
这些协调工作是由一组特殊的蛋白质来完成的。分子开关Ypt 控制细胞膜上的小囊在细胞器之间的进出。通过催化蛋白的结合控制开关。一种称为TRAPP 的催化蛋白结合两个Ypt开关来快速的开关细胞中心的高尔基体。
高尔基体通过细胞内的运输成为所有细胞的中心发电站，Segev 说。
伊利诺斯州立大学的研究人员在早些时候就已经证实TRAPP的亚基在协调控制高尔基体的开关和运输数量中起着关键的作用。现在他们指出TRAPP的组成成分依次的控制着运输。某一种构型的TRAPP结合了第一个Ypt使高尔基体开放，在高尔基体的另一端，就有两个亚基与TRAPP结合来激活Ypt使高尔基体关闭，Segev说。
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作者:admin@医学,生命科学 2010-11-08 17:11
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