Department of Experimental Medicine, Section of Microbiology and Clinical Microbiology, Second University of Naples, Naples 80138, Italy.
J Interferon Cytokine Res. 2009 Dec;29(12):791-800. doi: 10.1089/jir.2009.0010.
Biological membranes are described as a mosaic of different domains where interactions between membrane components induce the formation of subdomains with different characteristics and functions. Lipids play an important role in the formation of lipid-enriched microdomains where they dynamically associate to form platforms important for membrane protein sorting and construction of signaling complexes. Cholesterol confined in lipid domains is a crucial component required by microorganisms, directly or indirectly, to enter or exit the intracellular compartment. Cellular activation mediated by superficial bacterial component may be modified by local cholesterol depletion. Therefore, new perspectives for unconventional therapeutic intervention in Gram-negative infections may be envisaged. We tested this hypothesis by using methyl-beta-cyclodextrin (mbetaCD) as a cholesterol-complexing agent to alter the U937 plasma membrane cholesterol content. Our results demonstrate that cholesterol depletion of U937 cells inhibited Salmonella enterica serovar Typhimurium porins-mediated phosphorylation of Src kinase family, protein kinase C (PKC), JNK, and p38, while cholesterol repletion restored the phosphorylation. Lipopolysaccharide (LPS) extracted from the same bacterial strain has been used as a control. Our data demonstrate that the lack of activation of signal transduction pathway observed following cholesterol depletion differently modulates the release of interleukin-6 (IL-6) or tumor necrosis factor-alpha (TNF-alpha), suggesting that Src, associated to lipid domains, may represent an important pathway in Gram-negative-induced cellular signal.
生物膜被描述为不同结构域的镶嵌体，其中膜成分之间的相互作用诱导具有不同特征和功能的亚域的形成。脂质在富含脂质的微域的形成中起着重要作用，在这些微域中，它们动态地结合形成对膜蛋白分选和信号复合物构建很重要的平台。胆固醇局限于脂质域中，是微生物直接或间接进入或离开细胞内区室所必需的关键成分。通过表面细菌成分介导的细胞激活可能会被局部胆固醇耗竭所改变。因此，可以设想针对革兰氏阴性感染的非常规治疗干预的新视角。我们通过使用甲基-β-环糊精（mbetaCD）作为胆固醇络合剂来改变 U937 质膜胆固醇含量来测试这一假设。我们的结果表明，U937 细胞胆固醇耗竭抑制了沙门氏菌肠炎血清型 Typhimurium 孔蛋白介导的Src 激酶家族、蛋白激酶 C（PKC）、JNK 和 p38 的磷酸化，而胆固醇再补充则恢复了磷酸化。从同一细菌株提取的脂多糖（LPS）已被用作对照。我们的数据表明，胆固醇耗竭后观察到的信号转导途径激活缺失不同地调节白细胞介素 6（IL-6）或肿瘤坏死因子-α（TNF-α）的释放，表明与脂质域相关的 Src 可能代表革兰氏阴性诱导的细胞信号中的重要途径。
