title: Missing-in-metastasis and IRSp53 deform PI(4,5)P2-rich membranes by an inverse BAR domain-like mechanism.
abstract: The actin cytoskeleton plays a fundamental role in various motile and morphogenetic processes involving membrane dynamics. We show that actin-binding proteins MIM (missing-in-metastasis) and IRSp53 directly bind PI(4,5)P(2)-rich membranes and deform them into tubular structures. This activity resides in the N-terminal IRSp53/MIM domain (IMD) of these proteins, which is structurally related to membrane-tubulating BAR (Bin/amphiphysin/Rvs) domains. We found that because of a difference in the geometry of the PI(4,5)P(2)-binding site, IMDs induce a membrane curvature opposite that of BAR domains and deform membranes by binding to the interior of the tubule. This explains why IMD proteins induce plasma membrane protrusions rather than invaginations. We also provide evidence that the membrane-deforming activity of IMDs, instead of the previously proposed F-actin-bundling or GTPase-binding activities, is critical for the induction of the filopodia/microspikes in cultured mammalian cells. Together, these data reveal that interplay between actin dynamics and a novel membrane-deformation activity promotes cell motility and morphogenesis.
authors: Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland.
authors: Pieta K
authors: PK
authors: Mattila
authors: Anette
authors: A
authors: Pykäläinen
authors: Juha
authors: J
authors: Saarikangas
authors: Ville O
authors: VO
authors: Paavilainen
authors: Helena
authors: H
authors: Vihinen
authors: Eija
authors: E
authors: Jokitalo
authors: Pekka
authors: P
authors: Lappalainen
mesh_terms: D000199:Actins / Q000378:metabolism* / Q000648:ultrastructure; D001665:Binding Sites / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000502:physiology; D022081:Cell Surface Extensions / Q000378:metabolism* / Q000648:ultrastructure; D006801:Humans; D008840:Microfilament Proteins / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism; D008958:Models, Molecular; D009363:Neoplasm Proteins / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology; D011554:Pseudopodia / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D000199:Actins; C119539:BAIAP2 protein, human; C486778:MTSS1 protein, human; D008840:Microfilament Proteins; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D019269:Phosphatidylinositol 4,5-Diphosphate