title: Differing and isoform-specific roles for the formin DIAPH3 in plasma membrane blebbing and filopodia formation.
abstract: Plasma membrane (PM) blebs are dynamic actin-rich cell protrusions that occur, e.g., during cytokinesis, amoeboid cell motility and cell attachment. Using a targeted siRNA screen against 21 actin nucleation factors, we identify a novel and essential role of the human diaphanous formin DIAPH3 in PM blebbing during cell adhesion. Suppression of DIAPH3 inhibited blebbing to promote rapid cell spreading involving β1-integrin. Multiple isoforms of DIAPH3 were detected on the mRNA and protein level of which isoforms 3 and 7 were the largest and most abundant isoforms that however did not induce formation of actin-rich protrusions. Rather, PM blebbing specifically involved the low abundance isoform 1 of DIAPH3 and activation of isoform 7 by deletion of the diaphanous-autoregulatory domain caused the formation of filopodia. Dimerization and actin assembly activity were essential for induction of specific cell protrusions by DIAPH3 isoforms 1 and 7. Our data suggest that the N-terminal region comprising the GTPase-binding domain determined the subcellular localization of the formin as well as its protrusion activity between blebs and filopodia. We propose that isoform-selective actin assembly by DIAPH3 exerts specific and differentially regulated functions during cell adhesion and motility.
authors.affiliation: Department of Infectious Diseases, Virology, University Hospital Heidelberg, Heidelberg, Germany.
authors.forename: Jana
authors.initials: J
authors.lastname: Stastna
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Pan
authors.forename: Haicui
authors.initials: H
authors.lastname: Wang
authors.forename: Alina
authors.initials: A
authors.lastname: Kollmannsperger
authors.forename: Stefan
authors.initials: S
authors.lastname: Kutscheidt
authors.forename: Volker
authors.initials: V
authors.lastname: Lohmann
authors.forename: Robert
authors.initials: R
authors.lastname: Grosse
authors.forename: Oliver T
authors.initials: OT
authors.lastname: Fackler
mesh_terms: D000199:Actins / Q000378:metabolism* / Q000502:physiology; D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D002448:Cell Adhesion / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism* / Q000648:ultrastructure; D002465:Cell Movement / Q000502:physiology; D019281:Dimerization; D000080865:Formins; D015870:Gene Expression; D006367:HeLa Cells; D006801:Humans; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011554:Pseudopodia / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D034741:RNA, Small Interfering
chemical_list: D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; C484571:DIAPH3 protein, human; D000080865:Formins; D020033:Protein Isoforms; D034741:RNA, Small Interfering