Caveolin limits membrane microdomain mobility and integrin-mediated uptake of fibronectin-binding pathogens

Abstract

SummaryStaphylococcus aureus, which is a leading cause of hospital-acquired infections, binds via fibronectin to integrin 51, a process that can promote host colonization in vivo. Integrin engagement induces actin cytoskeleton rearrangements that result in the uptake of S. aureus by non-professional phagocytic cells. Interestingly, we found that fibronectin-binding S. aureus trigger the redistribution of membrane microdomain components. In particular, ganglioside GM1 and GPI-linked proteins were recruited upon integrin 1 engagement, and disruption of membrane microdomains blocked bacterial internalization. Several membrane-microdomain-associated proteins, such as flotillin-1 and flotillin-2, as well as caveolin, were recruited to sites of bacterial attachment. Whereas dominantnegative versions of flotillin-2 did not affect bacterial attachment or internalization, cells deficient for caveolin-1 (Cav1 -/-) showed increased uptake of S. aureus and other Fn-binding pathogens. Recruitment of membrane microdomains to cell-associated bacteria was unaltered in Cav1 -/-cells. However, fluorescence recovery after photobleaching (FRAP) revealed an enhanced mobility of membranemicrodomain-associated proteins in the absence of caveolin-1. Enhanced membrane microdomain mobility and increased uptake of S. aureus was repressed by expression of wild-type caveolin-1, but not caveolin-1 G83S, which harbors a point mutation in the caveolin scaffolding domain. Similarly, chemical or physical stimulation of membrane fluidity led to increased uptake of S. aureus. These results highlight a crucial role for caveolin-1 in negative regulation of membrane microdomain mobility, thereby affecting endocytosis of bacteria-engaged integrins. This process might not only limit host cell invasion by integrin-binding bacterial pathogens, but might also be physiologically relevant for integrin-mediated cell adhesion.

The Tetherin/BST-2 Coiled-Coil Ectodomain Mediates Plasma Membrane Microdomain Localization and Restriction of Particle Release

“…GPI-GFP and ICAM-1 GFP were used as controls for our FRAP experiments and exhibited mean D values of 0.33 and 0.10 m 2 /s, respectively. The membrane mobility exhibited by GPI-GFP correlates well to established membrane diffusion rates previously reported for this construct (11). All of the ectodomain mutants in this panel with a particle retention deficit displayed greater membrane diffusion rates than ICAM-1-GFP (Fig.…”

Identification of Equine Lactadherin-derived Peptides That Inhibit Rotavirus Infection via Integrin Receptor Competition

“…It is also possible that integrin-bound pDGE-RGD is endocytosed and inhibits virion conversion into the transcriptionally active, double-layered particle, which for Wa has been proposed to occur during exit from late endosomes (56). Interestingly, Wa VP8* binds the GM1 ganglioside, which can associate with integrins such as ␣5␤1 and ␣2␤1 in membrane microdomains (57,58) and has been proposed to classify cargo for uptake and trafficking in late endosomes (59). Binding of pDGE-RGD to ␤1 integrins internalized in endosomes also might interfere with Wa access to the cytoplasm, which is essential for replication (60).…”

Caveolae regulate the nanoscale organization of the plasma membrane to remotely control Ras signaling

“…Mobility of lipid components is altered dependent on CAV1 expression, ordered domains are less abundant, and accelerated endocytosis has been observed in caveolin-deficient cells (Gaus et al, 2006;Hernández-Deviez et al, 2008;Hoffmann et al, 2010). CAV1 can bind cholesterol and cholesterol depletion affects both CAV1 expression and the T he molecular mechanisms whereby caveolae exert control over cellular signaling have to date remained elusive.…”