Palmitoylation of the murine leukemia virus envelope protein is critical for lipid raft association and surface expression |
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Authors: | Li Min Yang Chinglai Tong Suxiang Weidmann Armin Compans Richard W |
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Affiliation: | Department of Microbiology and Immunology and Emory Vaccine Center, Emory University School of Medicine, Atlanta, Georgia 30322, USA. |
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Abstract: | To investigate the association of the murine leukemia virus (MuLV) Env protein with lipid rafts, we compared wild-type and palmitoylation-deficient mutant Env proteins by using extraction with the mild detergent Triton X-100 (TX-100) followed by a sucrose gradient flotation assay. We found that the wild-type MuLV Env protein was resistant to ice-cold TX-100 treatment and floated to the top of the gradients. In contrast, we observed that the palmitoylation-deficient mutant Env protein was mostly soluble when extracted by ice-cold TX-100 and stayed at the bottom of the gradients. Both the wild-type and mutant Env proteins were found to be soluble when treated with methyl-beta-cyclodextrin before extraction with ice-cold TX-100 or when treated with ice-cold octyl-beta-glucoside instead of TX-100. These results indicate that the MuLV Env protein is associated with lipid rafts and that palmitoylation of the Env protein is critical for lipid raft association. Although the palmitoylation-deficient Env mutant was synthesized at a level similar to that of the wild-type Env, it was found to be expressed at reduced levels on the cell surface. We observed syncytium formation activity with both the wild-type and mutant Env proteins, indicating that palmitoylation or raft association is not required for MuLV viral fusion activity. |
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