The Dioxin receptor modulates Caveolin-1 mobilization during directional migration: role of cholesterol

Abstract

BackgroundAdhesion and migration are relevant physiological functions that must be regulated by the cell under both normal and pathological conditions. The dioxin receptor (AhR) has emerged as a transcription factor regulating both processes in mesenchymal, epithelial and endothelial cells. Indirect results suggest that AhR could cooperate not only with additional transcription factors but also with membrane-associated proteins to drive such processes.ResultsIn this study, we have used immortalized and primary dermal fibroblasts from wild type (AhR+/+) and AhR-null (AhR−/−) mice to show that AhR modulates membrane distribution and mobilization of caveolin-1 (Cav-1) during directional cell migration. AhR co-immunoprecipitated with Cav-1 and a fraction of both proteins co-localized to detergent-resistant membrane microdomains (DRM). Consistent with a role of AhR in the process, AhR−/− cells had a significant reduction in Cav-1 in DRMs. Moreover, high cell density reduced AhR nuclear levels and moved Cav-1 from DRMs to the soluble membrane in AhR+/+ but not in AhR−/− cells. Tyrosine-14 phosphorylation had a complex role in the mechanism since its upregulation reduced Cav-1 in DRMs in both AhR+/+ and AhR−/−cells, despite the lower basal levels of Y14-Cav-1 in the null cells. Fluorescence recovery after photobleaching revealed that AhR knock-down blocked Cav-1 transport to the plasma membrane, a deficit possibly influencing its depleted levels in DRMs. Membrane distribution of Cav-1 in AhR-null fibroblasts correlated with higher levels of cholesterol and with disrupted membrane microdomains, whereas addition of exogenous cholesterol changed the Cav-1 distribution of AhR+/+ cells to the null phenotype. Consistently, higher cholesterol levels enhanced caveolae-dependent endocytosis in AhR-null cells.ConclusionsThese results suggest that AhR modulates Cav-1 distribution in migrating cells through the control of cholesterol-enriched membrane microdomains. Our study also supports the likely possibility of membrane-related, transcription factor independent, functions of AhR.Electronic supplementary materialThe online version of this article (doi:10.1186/s12964-014-0057-7) contains supplementary material, which is available to authorized users.

Environmental carcinogenesis and pH homeostasis: Not only a matter of dysregulated metabolism

“…In this way, PAHs promote their own metabolism [33,34]. It is worth noting that AhR has also been found to activate non-genomic pathways, notably in link to plasma membrane [35,36] and/or to mitochondrial location [37,38].…”

Alu retrotransposons modulate Nanog expression through dynamic changes in regional chromatin conformation via aryl hydrocarbon receptor

“…Nuclear and cytosolic cellular extracts were prepared for NTERA-wt and NTERA-sh as described previously [46]. SDS-PAGE and western blotting for both cell lines were performed as indicated [47].…”

Evidence of selective activation of aryl hydrocarbon receptor nongenomic calcium signaling by pyrene

“…and blocks TRPC and voltage gated channels, thus preventing extracellular Ca 2+ -entry. By contrast, the commonly used IP3R inhibitor 2APB (39,40), also suppressed the initial phase of pyrene-induced (44,45). AhR-expression also appears to regulate Cav1-localization in ordered microdomains, and that addition of cholesterol may switch the pattern of Cav1 localisation to a AhR-/-phenotype (45).…”

“…By contrast, the commonly used IP3R inhibitor 2APB (39,40), also suppressed the initial phase of pyrene-induced (44,45). AhR-expression also appears to regulate Cav1-localization in ordered microdomains, and that addition of cholesterol may switch the pattern of Cav1 localisation to a AhR-/-phenotype (45). Caveolae function as Ca 2+ -signaling microdomains regulating SOCE channels, where Cav1 may act by coupling IP3R with TRPC-channels (36,46).…”