Werthén M, Lundgren T
Department of Cell and Molecular Biology/Microbiology, Göteborg University, Göteborg SE-405 30, Sweden.
J Biol Chem. 2001 Mar 2;276(9):6468-72. doi: 10.1074/jbc.M009223200. Epub 2000 Dec 1.
Quorum sensing in Gram-negative bacteria involves acylated homoserine lactones (AHLs) and a transcription factor, activated by the AHLs. In this study, a possible involvement of intracellular Ca(2+) as second messenger and/or protein kinase activity during signal transduction is analyzed. When N-hexanoyl-l-homoserine lactone was added to a suspension of Fura-2-loaded Serratia liquefaciens, there was a decline in Ca(2+), measured as a decrease in the Fura-2 fluorescence ratio. As controls, the addition of the signal molecule N-3-oxohexanoyl-l-homoserine lactone, which is not produced by S. liquefaciens, did not induce changes in Ca(2+). Using a protein kinase activity assay on AHL-stimulated cells, an increase in kinase activity after N-butanoyl-l-homoserine lactone stimulation of S. liquefaciens cells was detected, whereas the kinase activity induced by N-3-oxohexanoyl-l-homoserine lactone was not statistically significant. The conclusion from this study is that changes in Ca(2+) are involved in quorum sensing signal transduction in the Gram-negative bacteria S. liquefaciens. We also conclude that kinase activity is induced in S. liquefaciens upon AHL stimulation. We suggest that the transient intracellular [Ca(2+)] changes and kinase activity, activated by the AHL signal, are critical for the quorum-sensing signal transduction.
革兰氏阴性菌中的群体感应涉及酰化高丝氨酸内酯（AHLs）和一种由AHLs激活的转录因子。在本研究中，分析了细胞内Ca(2+)作为第二信使和/或蛋白激酶活性在信号转导过程中可能的参与情况。当将N-己酰基-L-高丝氨酸内酯添加到负载Fura-2的液化沙雷氏菌悬浮液中时，[Ca(2+)]i下降，这通过Fura-2荧光比率的降低来衡量。作为对照，添加液化沙雷氏菌不产生的信号分子N-3-氧代己酰基-L-高丝氨酸内酯不会诱导[Ca(2+)]i发生变化。对AHL刺激的细胞进行蛋白激酶活性测定，检测到丁酰基-L-高丝氨酸内酯刺激液化沙雷氏菌细胞后激酶活性增加，而N-3-氧代己酰基-L-高丝氨酸内酯诱导的激酶活性无统计学意义。本研究的结论是，[Ca(2+)]i的变化参与了革兰氏阴性菌液化沙雷氏菌的群体感应信号转导。我们还得出结论，AHL刺激会诱导液化沙雷氏菌中的激酶活性。我们认为，由AHL信号激活的细胞内[Ca(2+)]的瞬时变化和激酶活性对于群体感应信号转导至关重要。
