Iomini Carlo, Li Linya, Mo Wenjun, Dutcher Susan K, Piperno Gianni
Department of Molecular, Cellular, and Developmental Biology, Mount Sinai School of Medicine, 1 Gustave L. Levy Place, Box 1007, New York, New York 10029, USA.
Curr Biol. 2006 Jun 6;16(11):1147-53. doi: 10.1016/j.cub.2006.04.035.
Ciliary membranes have a large repertoire of receptors and ion channels that act to transduce information from the environment to the cell. Chlamydomonas offers a tractable system for dissecting the transport and function of ciliary and flagellar membrane proteins. Isolation of ergosterol and sphingolipid-enriched Chlamydomonas flagellar membrane domains identified potential signaling molecules by mass spectroscopy. These include a membrane protein and a matrix flavodoxin protein that are encoded by the AGG2 and AGG3 genes, respectively. Agg2p localizes to the proximal flagellar membrane near the basal bodies. Agg3p is distributed throughout the flagellar matrix, with an increased concentration in the proximal regions where Agg2p is located. Chlamydomonas cells sense light by using a microbial-type rhodopsin , transduce a signal from the cell body to the flagella, and alter the waveform of the flagella to turn a cell toward the light. Protein depletion by RNA interference reveals that both AGG gene products play roles in the orientation of cells to a directional light source. The depleted strains mimic the phenotype of the previously identified agg1 mutant, which swims away from light. We propose that the localization of Agg2p and Agg3p to the proximal region of the flagella may be important for interpreting light signals.
纤毛膜拥有大量的受体和离子通道，这些受体和离子通道负责将来自环境的信息传递给细胞。衣藻为剖析纤毛和鞭毛膜蛋白的转运及功能提供了一个易于处理的系统。通过质谱分析，从富含麦角固醇和鞘脂的衣藻鞭毛膜结构域中分离出潜在的信号分子。其中包括分别由AGG2和AGG3基因编码的一种膜蛋白和一种基质黄素氧还蛋白。Agg2p定位于基体附近的近端鞭毛膜。Agg3p分布于整个鞭毛基质中，在Agg2p所在的近端区域浓度增加。衣藻细胞通过使用一种微生物型视紫红质来感知光线，将信号从细胞体传递到鞭毛，并改变鞭毛的波形，使细胞转向光线。通过RNA干扰使蛋白质缺失的实验表明，两个AGG基因产物在细胞朝向定向光源的定向过程中都发挥作用。缺失菌株模拟了之前鉴定出的agg1突变体的表型，即远离光线游动。我们认为Agg2p和Agg3p在鞭毛近端区域的定位可能对解读光信号很重要。
