The raft-promoting property of virion-associated cholesterol, but not the presence of virion-associated Brij 98 rafts, is a determinant of human immunodeficiency virus type 1 infectivity.
Lipid rafts are enriched in cholesterol and sphingomyelin and are isolated on the basis of insolubility in detergents, such as Brij 98 and Triton X-100. Recent work by Holm et al. has shown that rafts insoluble in Brig 98 can be found in human immunodeficiency virus type 1 (HIV-1) virus-like particles, although it is not known whether raft-like structures are present in authentic HIV-1 and it is unclear whether a virion-associated raft-like structure is required for HIV replication. Independently, it was previously reported that virion-associated cholesterol is critical for HIV-1 infectivity, although the specific requirement of virion cholesterol in HIV-1 was not examined. In the present study, we have demonstrated that infectious wild-type HIV-1 contains Brij 98 rafts but only minimal amounts of Triton X-100 rafts. To directly assess the functional requirement of virion-associated rafts and various features of cholesterol on HIV-1 replication, we replaced virion cholesterol with exogenous cholesterol analogues that have demonstrated either raft-promoting or -inhibiting capacity in model membranes. We observed that variable concentrations of exogenous analogues are required to replace a defined amount of virion-associated cholesterol, showing that structurally diverse cholesterol analogues have various affinities toward HIV-1. We found that replacement of 50% of virion cholesterol with these exogenous cholesterol analogues did not eliminate the presence of Brij 98 rafts in HIV-1. However, the infectivity levels of the lipid-modified HIV-1s directly correlate with the raft-promoting capacities of these cholesterol analogues. Our data provide the first direct assessment of virion-associated Brij 98 rafts in retroviral replication and illustrate the importance of the raft-promoting property of virion-associated cholesterol in HIV-1 replication.
Campbell
Shahan
S
Macfarlane Burnet Institute for Medical Research and Public Health, Cnr Punt and Commercial Roads, Melbourne 3004, Victoria, Australia.
Gaus
Katharina
K
Bittman
Robert
R
Jessup
Wendy
W
Crowe
Suzanne
S
Mak
Johnson
J
D002499:Centrifugation, Density Gradient; D002784:Cholesterol / Q000502:physiology*; D015497:HIV-1 / Q000737:chemistry* / Q000502:physiology*; D006801:Humans; D015151:Immunoblotting; D008055:Lipids / Q000032:analysis; D008563:Membrane Lipids / Q000502:physiology*; D021962:Membrane Microdomains / Q000737:chemistry / Q000502:physiology*; D017830:Octoxynol; D010938:Plant Oils; D011092:Polyethylene Glycols; D014764:Viral Proteins / Q000032:analysis; D014771:Virion / Q000737:chemistry*; D014779:Virus Replication
D008055:Lipids; D008563:Membrane Lipids; D010938:Plant Oils; D014764:Viral Proteins; C050629:viral envelope lipids; D011092:Polyethylene Glycols; D017830:Octoxynol; C033084:polyethylene glycol oleyl ether; D002784:Cholesterol