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

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(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