Gupta Tarang, Mondal Anish Kumar, Pani Ipsita, Chattopadhyay Kausik, Pal Santanu Kumar
Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali, Knowledge City, Sector-81, SAS Nagar, Mohali 140306, India.
Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Knowledge City, Sector-81, SAS Nagar, Mohali 140306, India.
Soft Matter. 2022 Jul 20;18(28):5293-5301. doi: 10.1039/d2sm00447j.
Pore-forming toxins (PFTs) produced by pathogenic bacteria serve as prominent virulence factors with potent cell-killing activity. Most of the β-barrel PFTs form transmembrane oligomeric pores in the membrane lipid bilayer in the presence of cholesterol. The pore-formation mechanisms of the PFTs highlight well-orchestrated regulated events in the membrane environment, which involve dramatic changes in the protein structure and organization. Also, concerted crosstalk between protein and membrane lipid components appears to play crucial roles in the process. Membrane-damaging lesions formed by the pore assembly of the PFTs would also be expected to impose drastic alterations in the membrane organization, details of which remain obscure in most of the cases. Prior reports have established that aqueous interfaces of liquid crystals (LCs) offer promise as responsive interfaces for biomolecular events (at physiologically relevant concentrations), which can be visualized as optical signals. Inspired by this, herein, we sought to understand the lipid membrane interactions of a β-barrel PFT , cytolysin (VCC), using LC-aqueous interfaces. Our results show the formation of dendritic patterns upon the addition of VCC to the lipid embedded with cholesterol over the LC film. In contrast, we did not observe any LC reorientation upon the addition of VCC to the lipid-laden LC-aqueous interface in the absence of cholesterol. An array of techniques such as polarizing optical microscopy (POM), atomic force microscopy (AFM), and fluorescence measurements were utilized to decipher the LC response to the lipid interactions of VCC occurring at these interfaces. Altogether, the results obtained from our study provide a novel platform to explore the mechanistic aspects of the protein-membrane interactions, in the process of membrane pore-formation by the membrane-damaging PFTs.
致病细菌产生的成孔毒素（PFTs）是具有强大细胞杀伤活性的重要毒力因子。大多数β桶状PFTs在胆固醇存在的情况下，会在膜脂双层中形成跨膜寡聚孔。PFTs的成孔机制突出了膜环境中精心编排的调控事件，这涉及蛋白质结构和组织的显著变化。此外，蛋白质与膜脂成分之间的协同串扰似乎在这一过程中起着关键作用。由PFTs的孔组装形成的膜损伤病变预计也会使膜组织发生剧烈改变，而在大多数情况下，其细节仍不清楚。先前的报道表明，液晶（LCs）的水相界面有望作为生物分子事件的响应界面（在生理相关浓度下），这可以可视化为光学信号。受此启发，在此我们试图利用LC-水相界面来了解一种β桶状PFT——溶细胞素（VCC）与脂质膜的相互作用。我们的结果表明，在LC膜上向嵌入胆固醇的脂质中添加VCC后会形成树枝状图案。相比之下，在没有胆固醇的情况下，向富含脂质的LC-水相界面添加VCC后，我们没有观察到任何LC重排。我们利用了一系列技术，如偏振光学显微镜（POM）、原子力显微镜（AFM）和荧光测量，来解读LC对在这些界面发生的VCC脂质相互作用的响应。总之，我们研究获得的结果提供了一个新的平台，用于探索膜损伤性PFTs在膜成孔过程中蛋白质-膜相互作用的机制方面。
