Eukaryotic catecholamine hormones influence the chemotactic control of Vibrio campbellii by binding to the coupling protein CheW

In addition to their well-known role as stress-associated catecholamine hormones in animals and humans, epinephrine (EPI) and norepinephrine (NE) act as interkingdom signals between eukaryotic hosts and bacteria. However, the molecular basis of their effects on bacteria is not well understood. In initial phenotypic studies utilizing Vibrio campbellii as a model organism, we characterized the bipartite mode of action of catecholamines, which consists of promotion of growth under iron limitation, and enhanced colony expansion. In order to identify the molecular targets of the hormones, we designed and synthesized tailored probes for chemical proteomic studies. As the catechol group in EPI and NE acts as iron chelator and is prone to form a reactive quinone moiety, we devised a photoprobe based on the adrenergic agonist phenylephrine (PE), which solely influenced colony expansion on soft agar. Using this probe, we identified CheW, located at the core of the chemotaxis signaling network, as a major target. In vitro studies confirmed that EPI, NE, PE, as well as labetalol, a clinically applied antagonist, bind to purified CheW with affinity constants in the sub-micromolar range. In line with these findings, exposure of V. campbellii to these adrenergic agonists affects the chemotactic control of the bacterium. This study highlights a previously unknown effect of eukaryotic signaling molecules on bacterial motility.

肾上腺素（epinephrine, EPI）与去甲肾上腺素（norepinephrine, NE）除作为动物和人类中广为人知的应激相关儿茶酚胺（catecholamine）类激素外，还可充当真核宿主与细菌之间的跨界信号分子。然而，二者对细菌产生作用的分子基础尚未得到充分阐明。在以坎贝氏弧菌（Vibrio campbellii）为模式生物开展的初步表型研究中，我们明确了儿茶酚胺的双相作用模式：一是在铁限制条件下促进细菌生长，二是增强菌落扩展能力。为鉴定这些激素的分子靶标，我们设计并合成了适配化学蛋白质组学（chemical proteomic）研究的定制化探针。鉴于肾上腺素和去甲肾上腺素中的儿茶酚基团兼具铁螯合活性且易反应生成活性醌类结构，我们基于肾上腺素能激动剂苯肾上腺素（phenylephrine, PE）开发了一款光探针（photoprobe）——该探针仅在软琼脂培养基上可影响菌落扩展。利用该探针，我们鉴定出位于趋化信号网络核心的CheW蛋白为主要靶标。体外实验证实，肾上腺素、去甲肾上腺素、苯肾上腺素以及临床应用的拮抗剂拉贝洛尔（labetalol）均可与纯化的CheW蛋白结合，其亲和常数处于亚微摩尔（sub-micromolar）量级。与上述研究发现一致，将坎贝氏弧菌暴露于这些肾上腺素能激动剂后，该细菌的趋化调控过程会受到影响。本研究揭示了真核生物信号分子对细菌运动性的一种此前未被发现的调控作用。