title: Live-cell imaging in Caenorhabditis elegans reveals the distinct roles of dynamin self-assembly and guanosine triphosphate hydrolysis in the removal of apoptotic cells.
abstract: Dynamins are large GTPases that oligomerize along membranes. Dynamin's membrane fission activity is believed to underlie many of its physiological functions in membrane trafficking. Previously, we reported that DYN-1 (Caenorhabditis elegans dynamin) drove the engulfment and degradation of apoptotic cells through promoting the recruitment and fusion of intracellular vesicles to phagocytic cups and phagosomes, an activity distinct from dynamin's well-known membrane fission activity. Here, we have detected the oligomerization of DYN-1 in living C. elegans embryos and identified DYN-1 mutations that abolish DYN-1's oligomerization or GTPase activities. Specifically, abolishing self-assembly destroys DYN-1's association with the surfaces of extending pseudopods and maturing phagosomes, whereas inactivating guanosine triphosphate (GTP) binding blocks the dissociation of DYN-1 from these membranes. Abolishing the self-assembly or GTPase activities of DYN-1 leads to common as well as differential phagosomal maturation defects. Whereas both types of mutations cause delays in the transient enrichment of the RAB-5 GTPase to phagosomal surfaces, only the self-assembly mutation but not GTP binding mutation causes failure in recruiting the RAB-7 GTPase to phagosomal surfaces. We propose that during cell corpse removal, dynamin's self-assembly and GTP hydrolysis activities establish a precise dynamic control of DYN-1's transient association to its target membranes and that this control mechanism underlies the dynamic recruitment of downstream effectors to target membranes.
authors.affiliation: Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA.
authors.forename: Bin
authors.initials: B
authors.lastname: He
authors.forename: Xiaomeng
authors.initials: X
authors.lastname: Yu
authors.forename: Moran
authors.initials: M
authors.lastname: Margolis
authors.forename: Xianghua
authors.initials: X
authors.lastname: Liu
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Leng
authors.forename: Yael
authors.initials: Y
authors.lastname: Etzion
authors.forename: Fei
authors.initials: F
authors.lastname: Zheng
authors.forename: Nan
authors.initials: N
authors.lastname: Lu
authors.forename: Florante A
authors.initials: FA
authors.lastname: Quiocho
authors.forename: Dganit
authors.initials: D
authors.lastname: Danino
authors.forename: Zheng
authors.initials: Z
authors.lastname: Zhou
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D017209:Apoptosis / Q000502:physiology*; D017173:Caenorhabditis elegans / Q000166:cytology / Q000196:embryology / Q000502:physiology; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D034281:Dynamins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D010588:Phagosomes / Q000378:metabolism / Q000648:ultrastructure; D017434:Protein Structure, Tertiary; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D020696:rab5 GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D000090802:rab7 GTP-Binding Proteins
chemical_list: D029742:Caenorhabditis elegans Proteins; D011993:Recombinant Fusion Proteins; D000090802:rab7 GTP-Binding Proteins; D006160:Guanosine Triphosphate; D020691:rab GTP-Binding Proteins; D020696:rab5 GTP-Binding Proteins; D034281:Dynamins