TRANSDUCTION OF THE A SIGNAL IN MYXOCOCCUS DEVELOPMENT

粘球菌xanthus代表了一个很好的模式系统，以解决 细胞间信号通路如何控制多细胞 发展这些问题与所有正常的胚胎和成人有关。 这些细胞传递信号以协调生长和发育等过程， 分化，以及信号网络缺陷的细胞， 例如癌细胞。 通过早期多细胞发育的进展需要M。桑索斯 细胞感知并响应高细胞密度和营养限制。两 敏感的传感网络监测这些细胞外信号， M早期的关键检查点。xanthus发育这个检查点可以是 通过特定基因Spi的表达来监测。长期目标是 研究是为了确定：i）细胞如何感知和识别 细胞密度信号ii）细胞密度和营养感测如何 综合道路？（3）基因的改变与 表达和多细胞子实体的复杂行为反应 阵型？ spi三个关键调节子的鉴定与表征 SasS、SasR和SasN已经开始解决这些问题。使用 经典和分子遗传学与蛋白质生物化学相结合， 产生了一个假说的机制，这些蛋白质整合两者 细胞密度信号（细胞外A信号）和饥饿信号， 创造出控制大脑发育表达的回路， 应答spi基因。 为了验证这一假设，他们计划：i）分析SasS/SasR/SasN依赖的 整合细胞密度和饥饿信号在早期M。桑索斯 ii）产生体外转录系统以测试活性， iii）分析SasS/SasR途径的刺激 通过改变细胞表面完整性，和iv）研究 SasS/SasR非依赖性A信号转导途径。他们的最终目标是 重建完整的信号通路作为其功能的证据。

Myxococcus xanthus represents an excellent model system to address fundamental questions of how cell-cell signaling pathways control multicellular development. These questions are relevant to all normal embryonic and adult cells that transduce signals to coordinate processes such as growth and differentiation, as well as to cells that are defective in signaling networks, such as cancer cells. Progression through early multicellular development requires that M. xanthus cells sense and respond to a high cell density and nutrient limitation. Two sensitive sensing networks monitor these extracellular signals and converge at a critical checkpoint early in M. xanthus development. This check -point can be monitored by expression of a specific gene, spi. The long-term goals of this research are to determine: i) How do the cells sense and transduce the cell-density signal? ii) How are the cell-density- and nutrient-sensing pathways integrated? iii) What is the connection between the change in gene expression and the complex behavioral response of multicellular fruiting body formation? The identification and characterization of three critical regulators of spi expression, SasS, SasR, and SasN has begun to address these questions. Using classical and molecular genetics combined with protein biochemistry, they have generated a hypothesis for the mechanism by which these proteins integrate both the cell-density signal (extracellular A signal) and the starvation signal, creating the circuitry that controls the developmental expression of the responsive spi gene. To test this hypothesis, they plan to: i) analyze the SasS/SasR/SasN-dependent integration of cell density and starvation signals during early M. xanthus development, ii) generate an in vitro transcription system to test the activity of the SasS/SasR pathway, iii) analyze the stimulation of the SasS/SasR pathway by alterations in cell-surface integrity, and iv) investigate SasS/SasR-independent A signal transduction pathways. Their ultimate goal is to reconstitute the complete signaling pathway as proof of its function.