Infectious Diseases Translational Research Programme, Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117545.
Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore 308232.
Proc Natl Acad Sci U S A. 2021 Nov 9;118(45). doi: 10.1073/pnas.2103377118.
Many pathogenic bacteria are encased in a layer of capsular polysaccharide (CPS). This layer is important for virulence by masking surface antigens, preventing opsonophagocytosis, and avoiding mucus entrapment. The bacterial tyrosine kinase (BY-kinase) regulates capsule synthesis and helps bacterial pathogens to survive different host niches. BY-kinases autophosphorylate at the C-terminal tyrosine residues upon external stimuli, but the role of phosphorylation is still unclear. Here, we report that the BY-kinase CpsCD is required for growth in Cells lacking a functional or accumulated low molecular weight CPS and lysed because of the lethal sequestration of the lipid carrier undecaprenyl phosphate, resulting in inhibition of peptidoglycan (PG) synthesis. CpsC interacts with CpsD and the polymerase CpsH. CpsD phosphorylation reduces the length of CPS polymers presumably by controlling the activity of CpsC. Finally, pulse-chase experiments reveal the spatiotemporal coordination between CPS and PG synthesis. This coordination is dependent on CpsC and CpsD. Together, our study provides evidence that BY-kinases regulate capsule polymer length by fine-tuning CpsC activity through autophosphorylation.
许多病原菌都被一层荚膜多糖（CPS）包裹着。这层多糖对于病原菌的毒力非常重要，因为它可以掩盖表面抗原，防止调理吞噬作用，并避免被黏液困住。细菌酪氨酸激酶（BY-kinase）调节荚膜合成，帮助细菌病原体在不同的宿主小生境中生存。BY-kinase 在受到外部刺激时会在 C 末端的酪氨酸残基上自动磷酸化，但磷酸化的作用仍不清楚。在这里，我们报告说，BY-kinase CpsCD 是在细胞中生长所必需的，缺乏功能性的或则会积累低分子量的 CPS，并由于脂质载体十一磷酸泛酰巯基乙胺的致命隔离而裂解，导致肽聚糖（PG）合成受到抑制。CpsC 与 CpsD 和聚合酶 CpsH 相互作用。CpsD 的磷酸化作用可能通过控制 CpsC 的活性来缩短 CPS 聚合物的长度。最后，脉冲追踪实验揭示了 CPS 和 PG 合成之间的时空协调。这种协调依赖于 CpsC 和 CpsD。总之，我们的研究提供了证据，表明 BY-kinases 通过自动磷酸化来精细调节 CpsC 的活性，从而调节荚膜聚合物的长度。
