title: Archipelago architecture of the focal adhesion: membrane molecules freely enter and exit from the focal adhesion zone.
abstract: The focal adhesion (FA) is an integrin-based structure built in/on the plasma membrane, mechanically linking the extracellular matrix with the termini of actin stress fibers, providing key scaffolds for the cells to migrate in tissues. The FA was considered as a micron-scale, massive assembly of various proteins, although its formation and decomposition occur quickly in several to several 10 s of minutes. The mechanism of rapid FA regulation has been a major mystery in cell biology. Here, using fast single fluorescent-molecule imaging, we found that transferrin receptor and Thy1, non-FA membrane proteins, readily enter the FA zone, diffuse rapidly there, and exit into the bulk plasma membrane. Integrin β3 also readily enters the FA zone, and repeatedly undergoes temporary immobilization and diffusion in the FA zone, whereas approximately one-third of integrin β3 is immobilized there. These results are consistent with the archipelago architecture of the FA, which consists of many integrin islands: the membrane molecules enter the inter-island channels rather freely, and the integrins in the integrin islands can be rapidly exchanged with those in the bulk membrane. Such an archipelago architecture would allow rapid FA formation and disintegration, and might be applicable to other large protein domains in the plasma membrane.
authors.affiliation: Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Japan; Institute for Frontier Medical Sciences, Kyoto University, Kyoto 606-8507, Japan.
authors.forename: Akihiro C E
authors.initials: AC
authors.lastname: Shibata
authors.forename: Takahiro K
authors.initials: TK
authors.lastname: Fujiwara
authors.forename: Limin
authors.initials: L
authors.lastname: Chen
authors.forename: Kenichi G N
authors.initials: KG
authors.lastname: Suzuki
authors.forename: Yoshiro
authors.initials: Y
authors.lastname: Ishikawa
authors.forename: Yuri L
authors.initials: YL
authors.lastname: Nemoto
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Miwa
authors.forename: Ziya
authors.initials: Z
authors.lastname: Kalay
authors.forename: Rahul
authors.initials: R
authors.lastname: Chadda
authors.forename: Keiji
authors.initials: K
authors.lastname: Naruse
authors.forename: Akihiro
authors.initials: A
authors.lastname: Kusumi
mesh_terms: D000818:Animals; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism*; D004058:Diffusion; D022001:Focal Adhesions / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D039661:Integrin beta3 / Q000378:metabolism; D008954:Models, Biological; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D011990:Receptors, Transferrin / Q000378:metabolism; D018800:Thy-1 Antigens / Q000378:metabolism; D013997:Time Factors
chemical_list: D039661:Integrin beta3; D011506:Proteins; D011990:Receptors, Transferrin; D018800:Thy-1 Antigens