title: Sphingomyelin and cholesterol promote HIV-1 gp41 pretransmembrane sequence surface aggregation and membrane restructuring.
abstract: The interfacial sequence DKWASLWNWFNITNWLWYIK, preceding the transmembrane anchor of gp41 glycoprotein subunit, has been shown to be essential for fusion activity and incorporation into virions. HIV(c), a peptide representing this region, formed lytic pores in liposomes composed of the main lipids occurring in the human immunodeficiency virus, type 1 (HIV-1), envelope, i.e. 1-palmitoyl-2-oleoylphosphatidylcholine (POPC):sphingomyelin (SPM):cholesterol (Chol) (1:1:1 mole ratio), at low (>1:10,000) peptide-to-lipid mole ratio, and promoted the mixing of vesicular lipids at >1:1000 peptide-to-lipid mole ratios. Inclusion of SPM or Chol in POPC membranes had different effects. Whereas SPM sustained pore formation, Chol promoted fusion activity. Even if partitioning into membranes was not affected in the absence of both SPM and Chol, HIV(c) had virtually no effect on POPC vesicles. Conditions described to disturb occurrence of lateral separation of phases in these systems reproduced the high peptide-dose requirements for leakage as found in pure POPC vesicles and inhibited fusion. Surface aggregation assays using rhodamine-labeled peptides demonstrated that SPM and Chol promoted HIV(c) self-aggregation in membranes. Employing head-group fluorescent phospholipid analogs in planar supported lipid layers, we were able to discern HIV(c) clusters associated to ordered domains. Our results support the notion that the pretransmembrane sequence may participate in the clustering of gp41 monomers within the HIV-1 envelope, and in bilayer architecture destabilization at the loci of fusion.
authors.affiliation: Unidad de Biofísica (Centro Superior de Investigaciones Cientificas-Universidad del País Vasco) and Departamento de Bioquímica, Universidad del País Vasco, Apartado 644, 48080 Bilbao, Spain.
authors.forename: Asier
authors.initials: A
authors.lastname: Sáez-Cirión
authors.forename: Shlomo
authors.initials: S
authors.lastname: Nir
authors.forename: Maier
authors.initials: M
authors.lastname: Lorizate
authors.forename: Aitziber
authors.initials: A
authors.lastname: Agirre
authors.forename: Antonio
authors.initials: A
authors.lastname: Cruz
authors.forename: Jesús
authors.initials: J
authors.lastname: Pérez-Gil
authors.forename: José L
authors.initials: JL
authors.lastname: Nieva
mesh_terms: D002462:Cell Membrane / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism*; D015700:HIV Envelope Protein gp41 / Q000378:metabolism*; D007700:Kinetics; D008055:Lipids / Q000737:chemistry; D008856:Microscopy, Fluorescence; D010455:Peptides / Q000737:chemistry; D010743:Phospholipids / Q000378:metabolism; D011485:Protein Binding; D017433:Protein Structure, Secondary; D013109:Sphingomyelins / Q000378:metabolism*; D013997:Time Factors
chemical_list: D015700:HIV Envelope Protein gp41; D008055:Lipids; D010455:Peptides; D010743:Phospholipids; D013109:Sphingomyelins; D002784:Cholesterol