Khosla Meenal, Spiegelman George B, Weeks Gerald
Department of Microbiology and Immunology, University of British Columbia, , 300-6174 University Boulevard, Vancouver, BC, Canada V6T 1Z3.
Dev Biol. 2005 Aug 15;284(2):412-20. doi: 10.1016/j.ydbio.2005.05.037.
The disruption of the gene encoding the Dictyostelium Ras subfamily protein, RasC results in a strain that fails to aggregate with defects in both cAMP signal relay and chemotaxis. Restriction enzyme mediated integration disruption of a second gene in the rasC(-) strain resulted in cells that were capable of forming multicellular structures in plaques on bacterial lawns. The disrupted gene, designated pikD(1), encodes a member of the phosphatidyl-inositol-4-kinase beta subfamily. Although the rasC(-)/pikD(1) cells were capable of progressing through early development, when starved on a plastic surface under submerged conditions, they did not form aggregation streams or exhibit pulsatile motion. The rasC(-)/pikD(1) cells were extremely efficient in their ability to chemotax to cAMP in a spatial gradient, although the reduced phosphorylation of PKB in response to cAMP observed in rasC(-) cells, was unchanged. In addition, the activation of adenylyl cyclase, which was greatly reduced in the rasC(-) cells, was only minimally increased in the rasC(-)/pikD(1) strain. Thus, although the rasC(-)/pikD(-) cells were capable of associating to form multicellular structures, normal cell signaling was clearly not restored. The disruption of the pikD gene in a wild type background resulted in a strain that was delayed in aggregation and formed large aggregation streams, when starved on a plastic surface under submerged conditions. This strain also exhibited a slight defect in terminal development. In conclusion, disruption of the pikD gene in a rasC(-) strain resulted in cells that were capable of forming multicellular structures, but which did so in the absence of normal signaling and aggregation stream formation.
编码盘基网柄菌Ras亚家族蛋白RasC的基因发生破坏，会导致菌株无法聚集，在cAMP信号转导和趋化性方面均存在缺陷。在rasC(-)菌株中，通过限制酶介导的整合破坏第二个基因，产生的细胞能够在细菌菌苔上的噬菌斑中形成多细胞结构。被破坏的基因命名为pikD(1)，编码磷脂酰肌醇-4-激酶β亚家族的一个成员。尽管rasC(-)/pikD(1)细胞能够进行早期发育，但在水下塑料表面饥饿时，它们不会形成聚集流，也不表现出脉动运动。rasC(-)/pikD(1)细胞在空间梯度中对cAMP进行趋化的能力非常高效，不过在rasC(-)细胞中观察到的对cAMP应答时蛋白激酶B（PKB）磷酸化减少的情况没有改变。此外，在rasC(-)细胞中大幅降低的腺苷酸环化酶的激活，在rasC(-)/pikD(1)菌株中仅略有增加。因此，尽管rasC(-)/pikD(-)细胞能够聚集形成多细胞结构，但正常的细胞信号显然没有恢复。在野生型背景下破坏pikD基因，产生的菌株在水下塑料表面饥饿时聚集延迟，形成大的聚集流。该菌株在终末发育中也表现出轻微缺陷。总之，在rasC(-)菌株中破坏pikD基因导致细胞能够形成多细胞结构，但这是在缺乏正常信号传导和聚集流形成的情况下发生的。
