Single-molecule analysis of CD9 dynamics and partitioning reveals multiple modes of interaction in the tetraspanin web.
Tetraspanins regulate cell migration, sperm-egg fusion, and viral infection. Through interactions with one another and other cell surface proteins, tetraspanins form a network of molecular interactions called the tetraspanin web. In this study, we use single-molecule fluorescence microscopy to dissect dynamics and partitioning of the tetraspanin CD9. We show that lateral mobility of CD9 in the plasma membrane is regulated by at least two modes of interaction that each exhibit specific dynamics. The majority of CD9 molecules display Brownian behavior but can be transiently confined to an interaction platform that is in permanent exchange with the rest of the membrane. These platforms, which are enriched in CD9 and its binding partners, are constant in shape and localization. Two CD9 molecules undergoing Brownian trajectories can also codiffuse, revealing extra platform interactions. CD9 mobility and partitioning are both dependent on its palmitoylation and plasma membrane cholesterol. Our data show the high dynamic of interactions in the tetraspanin web and further indicate that the tetraspanin web is distinct from raft microdomains.
Espenel
Cedric
C
Institut National de la Santé et de la Recherche Medicale, Unité 554, Montpellier, France.
Margeat
Emmanuel
E
Dosset
Patrice
P
Arduise
Cécile
C
Le Grimellec
Christian
C
Royer
Catherine A
CA
Boucheix
Claude
C
Rubinstein
Eric
E
Milhiet
Pierre-Emmanuel
PE
D015703:Antigens, CD / Q000378:metabolism*; D018958:CD55 Antigens / Q000378:metabolism; D002451:Cell Compartmentation / Q000187:drug effects; D045744:Cell Line, Tumor; D002784:Cholesterol / Q000494:pharmacology; D004058:Diffusion / Q000187:drug effects; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism*; D021962:Membrane Microdomains / Q000187:drug effects / Q000378:metabolism; D019308:Palmitic Acid / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D060245:Tetraspanin 29; D047392:beta-Cyclodextrins / Q000494:pharmacology
D015703:Antigens, CD; D018958:CD55 Antigens; C554869:CD9 protein, human; D008562:Membrane Glycoproteins; D060245:Tetraspanin 29; D047392:beta-Cyclodextrins; D019308:Palmitic Acid; D002784:Cholesterol; C031215:betadex