Multimodal and Polymorphic Interactions between Anillin and Actin: Their Implications for Cytokinesis.
Cytokinesis of animal cells requires the assembly of a contractile ring, which promotes daughter cell splitting. Anillin is a conserved scaffold protein involved in organizing the structural components of the contractile ring including filamentous actin (F-actin), myosin, and septins and in forming the subsequent midbody ring. Like other metazoan homologs, Drosophila anillin contains a conserved domain that can bind and bundle F-actin, but the importance and molecular details of its interaction with F-actin remain unclear. Here, we show that in a depletion-and-rescue assay in Drosophila S2 cells, anillin lacking the entire actin-binding domain (ActBD) exhibits defective cortical localization during mitosis and a greatly diminished ability to support cytokinesis. Using in vitro binding assays and electron microscopy on recombinant fragments, we determine that the anillin ActBD harbors three distinct actin-binding sites (ABS 1-3). We show that each ABS binds to a distinct place on F-actin. Importantly, ABS1 and ABS3 partially overlap on the surface of actin and, therefore, interact with F-actin in a mutually exclusive fashion. Although ABS2 and ABS3 are sufficient for bundling, ABS1 contributes to the overall F-actin bundling activity of anillin and enables anillin to switch between two actin-bundling morphologies and promote the formation of three-dimensional F-actin bundles. Finally, we show that in live S2 cells, ABS2 and ABS3 are each required and together sufficient for the robust cortical localization of the ActBD during cytokinesis. Collectively, our structural, biochemical, and cell biological data suggest that multiple anillin-actin interaction modes promote the faithful progression of cytokinesis.
Sainte-Justine Hospital Research Center, 3175 Chemin de la Côte Ste-Catherine, Montréal, Québec H3T 1C5, Canada.
Silvana
S
Jananji
Department of Physiological Sciences, Eastern Virginia Medical School, Norfolk, VA 23507, USA.
Cristina
C
Risi
Institute for Research in Immunology and Cancer (IRIC), Université de Montréal, P.O. Box 6128, Station Centre-Ville, Montréal, Québec H3C 3J7, Canada.
Indeewari K S
IKS
Lindamulage
Sainte-Justine Hospital Research Center, 3175 Chemin de la Côte Ste-Catherine, Montréal, Québec H3T 1C5, Canada.
Louis-Philippe
LP
Picard
Department of Physiological Sciences, Eastern Virginia Medical School, Norfolk, VA 23507, USA.
Robert
R
Van Sciver
Institute for Research in Immunology and Cancer (IRIC), Université de Montréal, P.O. Box 6128, Station Centre-Ville, Montréal, Québec H3C 3J7, Canada.
Guillaume
G
Laflamme
Institute for Research in Immunology and Cancer (IRIC), Université de Montréal, P.O. Box 6128, Station Centre-Ville, Montréal, Québec H3C 3J7, Canada.
Abe
A
Albaghjati
Sainte-Justine Hospital Research Center, 3175 Chemin de la Côte Ste-Catherine, Montréal, Québec H3T 1C5, Canada; Département de Pathologie et Biologie Cellulaire, Université de Montréal, P.O. Box 6128, Station Centre-Ville, Montréal, Québec H3C 3J7, Canada. Electronic address: gilles.hickson@umontreal.ca.
Gilles R X
GRX
Hickson
Institute for Research in Immunology and Cancer (IRIC), Université de Montréal, P.O. Box 6128, Station Centre-Ville, Montréal, Québec H3C 3J7, Canada; Département de médecine, Université de Montréal, P.O. Box 6128, Station Centre-Ville, Montréal, Québec H3C 3J7, Canada. Electronic address: benjamin.kwok@umontreal.ca.
Benjamin H
BH
Kwok
Department of Physiological Sciences, Eastern Virginia Medical School, Norfolk, VA 23507, USA. Electronic address: galkinve@evms.edu.
Vitold E
VE
Galkin
D000199:Actins / Q000378:metabolism*; D000818:Animals; D003285:Contractile Proteins / Q000378:metabolism*; D048749:Cytokinesis; D004330:Drosophila / Q000378:metabolism; D007091:Image Processing, Computer-Assisted; D008938:Mitosis; D009218:Myosins; D054730:Protein Interaction Domains and Motifs; D058112:Septins
D000199:Actins; D003285:Contractile Proteins; C095886:anillin; D058112:Septins; D009218:Myosins
F-actin; actin bundling; anillin; cytokinesis; electron microscopy