title: Caveolin limits membrane microdomain mobility and integrin-mediated uptake of fibronectin-binding pathogens.
abstract: Staphylococcus aureus, which is a leading cause of hospital-acquired infections, binds via fibronectin to integrin α5β1, 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 β1 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 dominant-negative 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 membrane-microdomain-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.
authors.affiliation: Lehrstuhl Zellbiologie X908, Universität Konstanz, Universitätsstr. 10, 78457 Konstanz, Germany.
authors.forename: Christine
authors.initials: C
authors.lastname: Hoffmann
authors.forename: Anne
authors.initials: A
authors.lastname: Berking
authors.forename: Franziska
authors.initials: F
authors.lastname: Agerer
authors.forename: Alexander
authors.initials: A
authors.lastname: Buntru
authors.forename: Florian
authors.initials: F
authors.lastname: Neske
authors.forename: G Singh
authors.initials: GS
authors.lastname: Chhatwal
authors.forename: Knut
authors.initials: K
authors.lastname: Ohlsen
authors.forename: Christof R
authors.initials: CR
authors.lastname: Hauck
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000378:metabolism; D001798:Blood Proteins / Q000378:metabolism; D002417:Cattle; D051242:Caveolin 1 / Q000737:chemistry / Q000172:deficiency / Q000378:metabolism*; D004705:Endocytosis; D005347:Fibroblasts / Q000166:cytology / Q000201:enzymology / Q000382:microbiology / Q000648:ultrastructure; D005353:Fibronectins / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D019012:Integrin beta1 / Q000378:metabolism*; D021962:Membrane Microdomains / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D021381:Protein Transport; D013203:Staphylococcal Infections / Q000378:metabolism; D013211:Staphylococcus aureus / Q000166:cytology / Q000378:metabolism*; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D001798:Blood Proteins; D051242:Caveolin 1; C488964:Stom protein, mouse; D005353:Fibronectins; D019012:Integrin beta1; D008565:Membrane Proteins; C106354:flotillins; D019061:src-Family Kinases