Structural and functional modifications of neuronal lipid rafts: implications for HIV-associated neurological disorders

BACKGROUND: HIV-associated neurological disorders (HAND) remain a prevalent co-morbidity of HIV infection. Growing evidence implicates the HIV protein Nef in this process, as Nef increases the abundance of neuronal lipid rafts - cholesterol- and sphingolipid-rich membrane microdomains linked to neurodegeneration and neuroinflammation. Because Nef is released from infected glial cells in extracellular vesicles (exNef), we investigated whether glia-derived exNef alters the structural and functional properties of neuronal lipid rafts in a manner that could contribute to HAND pathogenesis. METHODS: A comprehensive lipidomics and proteomics analysis of lipid rafts isolated from cultured human neuronal cell line SH-SY5Y, combined with assessment of biophysical and physiological properties of the rafts, was performed. We compared our findings with existing transcriptomics profiles of brain neurons from individuals diagnosed with HAND. RESULTS: Lipidomics analysis of isolated neuronal lipid raft fractions revealed minimal impact of exNef on the raft lipid composition; physico-chemical properties of the lipid rafts were also unaffected. In contrast, proteomic analysis revealed that among raft proteins with increased abundance following exNef exposure ~25% were implicated in neurological disease pathways. Targeted protein analysis unveiled that exNef promotes the redistribution of several neurodegenerative and inflammatory proteins to the lipid rafts, resulting in increased inflammation and apoptosis alongside reduced neuronal excitability. Pharmacological disruption of raft elevation with the lipid raft antagonist Oxy210 reversed exNef-induced raft expansion and abrogated these structural and functional alterations. Importantly, changes in raft protein composition showed strong concordance with transcriptomic profiles from single-nucleus RNA sequencing (snRNA-seq) of brain from people living with HIV. CONCLUSIONS: ExNef reorganize the neuronal lipid raft proteome, enhancing the activity of neurodegenerative and inflammatory mediators. This phenomenon may potentially contribute to HAND pathogenesis.