Compartmentalization of proteasomes in lipid rafts and exosomes: unveiling molecular interactions in vaping-related...

Tobacco-based products, including e-cigarettes, have gained popularity as perceived safer alternatives to traditional smoking despite their addictive nature. However, emerging evidence shows that heating e-liquids generates aerosols containing harmful substances, including nicotine, aldehydes, metals, and fine/ultrafine particles. This aerosol composition varies significantly based on device settings, e-liquid ingredients, and heating conditions. E-cigarettes use has been associated with declining lung function, epithelial cell damage, inflammation, and oxidative stress. Previous studies have highlighted and identified the ubiquitin-proteasome system within the lipid raft proteome of murine macrophages, suggesting its role in modulating the NF-κB(p105)-MEK-ERK pathway and inflammatory responses. Based on these findings, our study aimed to investigate the effects of e-cigarette vapors on the compartmentalization of proteasomes. We exposed human type II lung alveolar epithelial cells (A549) to filtered air or tobacco-flavored e-cigarette vapor condensate (TF-ECVC; with or without nicotine) for 24 h. Our findings revealed a notable increase in the transcription and translation of lipid rafts-associated proteins, including Caveolin-1, Caveolin-2, Flotillin-1, and Flotillin-2. We performed subcellular fractionation to elucidate the localization of proteasome/immunoproteasome subunits along with lipid rafts-associated proteins in the membrane and cytosolic fractions. Furthermore, we also observed the localization of proteasome and immunoproteasome subunits within the lipid raft fractions of TF-ECVC-exposed alveolar epithelial cells. Notably, membrane rafts-associated proteins and proteasome subunits were significantly accumulated within exosomes released from the challenged cells. These findings underscore the role of membrane rafts in proteasome compartmentalization and highlight novel molecular mechanisms regulated by ECVC. Furthermore, this study provides critical insights into the potential health risks associated with e-cigarette usage, emphasizing the need for further investigation into its cellular effects.