title: Antagonistic regulation of F-BAR protein assemblies controls actin polymerization during podosome formation.
abstract: FBP17, an F-BAR domain protein, has emerged as a crucial factor linking the plasma membrane to WASP-mediated actin polymerization. Although it is well established that FBP17 has a powerful self-polymerizing ability that promotes actin nucleation on membranes in vitro, knowledge of inhibitory factors that counteract this activity in vivo is limited. Here, we demonstrate that the assembly of FBP17 on the plasma membranes is antagonized by PSTPIP2, another F-BAR protein implicated in auto-inflammatory disorder. Knockdown of PSTPIP2 in macrophage promotes the assembly of FBP17 as well as subsequent actin nucleation at podosomes, resulting in an enhancement of matrix degradation. This phenotype is rescued by expression of PSTPIP2 in a manner dependent on its F-BAR domain. Time-lapse total internal reflection fluorescence (TIRF) microscopy observations reveal that the self-assembly of FBP17 at the podosomal membrane initiates actin polymerization, whereas the clustering of PSTPIP2 has an opposite effect. Biochemical analysis and live-cell imaging show that PSTPIP2 inhibits actin polymerization by competing with FBP17 for assembly at artificial as well as the plasma membrane. Interestingly, the assembly of FBP17 is dependent on WASP, and its dissociation by WASP inhibition strongly induces a self-organization of PSTPIP2 at podosomes. Thus, our data uncover a previously unappreciated antagonism between different F-BAR domain assemblies that determines the threshold of actin polymerization for the formation of functional podosomes and may explain how the absence of PSTPIP2 causes auto-inflammatory disorder.
authors.affiliation: Division of Lipid Biochemistry, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, Hyogo 650-0017, Japan.
authors.forename: Kazuya
authors.initials: K
authors.lastname: Tsujita
authors.forename: Akihiro
authors.initials: A
authors.lastname: Kondo
authors.forename: Shusaku
authors.initials: S
authors.lastname: Kurisu
authors.forename: Junya
authors.initials: J
authors.lastname: Hasegawa
authors.forename: Toshiki
authors.initials: T
authors.lastname: Itoh
authors.forename: Tadaomi
authors.initials: T
authors.lastname: Takenawa
mesh_terms: D000199:Actins / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001327:Autoimmune Diseases / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D001667:Binding, Competitive; D019556:COS Cells; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D048708:Cell Growth Processes / Q000235:genetics; D002462:Cell Membrane / Q000378:metabolism*; D022081:Cell Surface Extensions / Q000378:metabolism* / Q000473:pathology; D002522:Chlorocebus aethiops; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D005109:Extracellular Matrix / Q000378:metabolism; D050556:Fatty Acid-Binding Proteins; D006801:Humans; D008264:Macrophages / Q000502:physiology*; D051379:Mice; D055503:Protein Multimerization / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D051316:Wiskott-Aldrich Syndrome Protein / Q000378:metabolism
chemical_list: D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; C433770:FNBP1 protein, human; D050556:Fatty Acid-Binding Proteins; C486383:Pstpip2 protein, mouse; D034741:RNA, Small Interfering; D051316:Wiskott-Aldrich Syndrome Protein
keywords: F-BAR domain; Podosome dynamics; WASP-mediated actin polymerization