Abstract
Purpose :
The role of Caveolin-1 (Cav1), the signature protein of caveolae, in regulation of innate immune response seems controversial, since Cav1 can either promote or suppress immune response in a cell-context manner. We speculate that caveolar and non-caveolar localization of Cav1 in different cells accounts for this paradoxical immune regulatory role. Here, we show that non-caveolar Cav1 in Müller glia enhance lipopolysaccharide (LPS)-induced interleukin-6 (IL-6) response, which can be blunted by either Cav1 silencing or sequestration into caveolae
Methods :
To investigate the role of non-caveolar Cav1 in immune regulation, we either silenced Cav1 using Cav1-shRNA, or sequestered Cav1 into caveolae by expressing Cavin1/PTRF in MIO-M1 Müller glia and measured IL-6 response in tissue culture media by ELISA, with or without LPS stimulation. We used quantitative proteomics to identify immune-related pathways enriched in Cav1 immunoprecipitates from control and Cavin1/PTRF-expressing MIO-M1 Müller glia. Additionally we performed immunocytochemistry staining of MIO-M1 Müller glia using fluorescently labeled phalloidin to evaluate changes in filamentous actin (F-actin) when Cavin1/PTRF is expressed
Results :
LPS stimulation of MIO-M1 Müller glia significantly increased IL-6 secretion into tissue culture media. Surprisingly, both Cav1 silencing or Cavin1/PTRF expression in MIO-M1 Müller glia significantly suppressed LPS-induced IL-6 response. Analysis of mass spectrometry data revealed significant differential association of different proteins with Cav1 when Cavin1/PTRF is expressed. Interestingly, we identified 18 genes in 11 of the 30 most enriched pathways for proteins with significantly increased association with Cav1 that were associated with immune-related pathways. These were distributed among seven distinct immune-related gene ontology (GO) functional categories including neutrophil activation, neutrophil degranulation, immune effector process and immune response. Furthermore, expression of Cavin1/PTRF in MIO-M1 Müller glia significantly reduced F-actin staining intensity
Conclusions :
Our results suggest that non-caveolar Cav1 in MIO-M1 Müller glia enhance LPS-induced innate immune response. Expression of Cavin1/PTRF sequesters Cav1 into caveolae, which alters critical pathways involved in immune regulation, with remodeling of actin cytoskeleton as a potential mechanism
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.