The role of host cell membrane lipids in infection of microorganisms and in host defense mechanisms

(1)杆状病毒gp64包膜糖蛋白是出芽病毒包膜的主要成分，参与病毒内吞进入宿主细胞。我们利用重组杆状病毒Ac64-CAluc研究了杆状病毒感染哺乳动物细胞的重要细胞表面分子，该重组杆状病毒在多面蛋白和CAG启动子下分别含有gp64和荧光素酶基因。纯化脂质的抑制作用和对缺乏磷脂合成的突变CHO仓鼠细胞系的易感性表明，gp64与细胞表面磷脂的相互作用可能在杆状病毒感染哺乳动物细胞的过程中起重要作用。(2)从发酵培养物MF6020中分离得到一种新型真菌鞘脂合成抑制剂khafrefungin，并合成了khafrefungin衍生物，测定了其抗真菌活性，以了解其结构-活性关系。这表明，C4位点的结构似乎是抑制IPC合成酶活性的关键，IPC合成酶是khafrefungin的靶酶。(3)细胞表面与toll样受体（TLR）4相关的MD-2的表达使TLR4对LPS和LPS模拟紫杉醇产生响应性。采用丙氨酸扫描诱变法鉴定小鼠MD-2残基，这些残基对小鼠TLR4产生LPS和紫杉醇响应性以及形成抗TLR4-MD-2 Ab MTS510识别的细胞表面TLR4-MD-2复合物具有重要作用。我们的研究结果表明，MD-2在细胞表面形成被MTS510识别的小鼠TLR4-小鼠MD-2复合物的能力对于赋予TLR4 LPS和紫杉醇响应性是必要的，但不是充分的。此外，小鼠MD-2产生LPS应答能力所需的密码子34、85、101、122和153位残基与产生紫杉醇应答能力的密码子残基部分不同。(4)黄磷脂是一种从脑膜炎败血症黄杆菌中分离出来的含氨基酸的脂质，可诱导多种免疫反应。在这项研究中，我们证明了TLR4-MD-2和CD14参与黄磷脂信号传导，以及黄磷脂脂质部分的(R)构型对通过TLR4-MD-2诱导免疫应答的重要性。少

(1)Baculovirus gp64 envelope glycoprotein is a major component of the envelope of the budded virus and is involved in virus entry into the host cells by endocytosis. We investigated the cell-surface molecules important for infection of baculoyirus into mammalian cells by using a recombinant baculovirus, Ac64-CAluc, which has gp64 and luciferase genes under the polyhedrin and the CAG promoter, respectively. Inhibition with purified lipids and susceptibility to the mutant CHO hamster cell lines deficient in phospholipids synthesis suggested that the interaction of gp64 and phospholipids on the cell surface might play an important role in baculovirus infection into mammalian cells.(2) A convergent total synthesis of khafrefungin, a novel inhibitor of fungal sphingolipid syntheses isolated from the fermentation culture MF6020, has been developed, Khafrefungin derivatives have also been synthesized, and their antifungal activities have been measured to obtain information on the structure-ac … More tivity relationships. It is suggested that the configuration of the C4 position in khafrefungin appears to be crucial for inhibiting the activity of IPC synthase, the target enzyme of khafrefungin.(3) The expression of MD-2, which associates with Toll-like receptor (TLR)4 on the cell surface, confers LPS and LPS-mimetic Taxol responsiveness on TLR4. Alanine-scanning mutagenesis was performed to identify the mouse MD-2 residues important for conferring LPS and Taxol responsiveness on mouse TLR4, and for forming the cell surface TLR4-MD-2 complex recognized by anti-TLR4-MD-2 Ab MTS510. Our results suggest that the ability of MD-2 to form the cell surface mouse TLR4-mouse MD-2 complex recognized by MTS510 is essential for conferring LPS and Taxol responsiveness on TLR4, but not sufficient. In addition, the required residues at codon numbers 34, 85, 101, 122, and 153 for the ability of mouse MD-2 to confer LPS responsiveness are partly different from those for Taxol responsiveness.(4) Flavolipin, an amino acid-containing lipid isolated from Flavobacterium meningosepticum, induces many immune responses. In this study, we demonstrated the involvement of TLR4-MD-2 and CD14 in flavolipin signaling and the importance of the(R)-configuration of the flavolipin lipid moiety for the induction of an immune response via TLR4-MD-2. Less