The myriad roles of Anillin during cytokinesis

Anillin is a highly conserved multidomain protein that interacts with cytoskeletal components as well as their regulators. Throughout phylogeny, Anillins contribute to cytokinesis, the cell shape change that occurs at the end of meiosis and mitosis to separate a cell into daughter cells. Failed cytokinesis results in binucleation, which can lead to genomic instability. Study of Anillin in several model organisms has provided us with insight into how the cytoskeleton is coordinated to ensure that cytokinesis occurs with high fidelity. Here we review Anillin’s interacting partners and the relevance of these interactions in vivo. We also discuss questions of how these interactions are coordinated, and finally provide some perspective regarding Anillin’s role in cancer

The Caenorhabditis elegans nonmuscle myosin genes nmy-1 and nmy-2 function as redundant components of the let-502/Rho-binding kinase and mel-11/myosin phosphatase pathway during embryonic morphogenesis

Rho-binding kinase and the myosin phosphatase targeting subunit regulate nonmuscle contractile events in higher eukaryotes. Genetic evidence indicates that the C. elegans homologs regulate embryonic morphogenesis by controlling the actin-mediated epidermal cell shape changes that transform the spherical embryo into a long, thin worm. LET-502/Rho-binding kinase triggers elongation while MEL-11/myosin phosphatase targeting subunit inhibits this contractile event. We describe mutations in the nonmuscle myosin heavy chain gene nmy-1 that were isolated as suppressors of the mel-11 hypercontraction phenotype. However, a nmy-1 null allele displays elongation defects less severe than mutations in let-502 or in the single nonmuscle myosin light chain gene mlc-4. This results because nmy-1 is partially redundant with another nonmuscle myosin heavy chain, nmy-2, which was previously known only for its role in anterior/posterior polarity and cytokinesis in the early embryo. At the onset of elongation, NMY-1 forms filamentous-like structures similar to actin, and LET-502 is interspersed with these structures, where it may trigger contraction. MEL-11, which inhibits elongation, is initially cytoplasmic. In response to LET-502 activity, MEL-11 becomes sequestered away from the contractile apparatus, to the plasma membrane, when elongation commences. Upon completion of morphogenesis, MEL-11 again appears in the cytoplasm where it may halt actin/myosin contraction

Dual disassembly and biological evaluation of enzyme/oxidation-responsive polyester-based nanoparticulates for tumor-targeting delivery

Polyester-based nanoparticulates (NPs) are ideal nanocarriers for intracellular delivery of anticancer drugs because of their biocompatibility. However, an on-going challenge is the controlled and enhanced release of encapsulated therapeutics in response to unique changes that occur within cancer cells. Herein, we report the versatility of dual responses to enzymatic and oxidative reactions found in cancer cells toward the development of polyester-NPs as effective tumor-targeting intracellular nanocarriers. A facile nanoprecipitation method allows for the preparation of hydrophobic cores composed of novel polyester designed with esterase-responsive ester groups and oxidation-responsive sulfide linkages on their backbones, physically stabilized with poly(ethylene glycol)-based polymeric shells. The formed core/shell-type NPs with a diameter of 120 nm exhibit excellent colloidal stability in physiological conditions and in the presence of serum proteins. When exposed to esterase and hydrogen peroxide, NP integrity is disrupted, leading to the enhanced release of encapsulated doxorubicin, confirmed by dynamic light scattering and spectroscopic analysis. Combined results from epifluorescence microscopy, confocal laser scanning microscopy, flow cytometry, and cell viability demonstrate that doxorubicin-loaded NPs reveal rapid penetration and enhanced intracellular release of doxorubicin, thus inhibiting tumor progression. Importantly, the cellular uptake of doxorubicin-loaded core/shell NPs primarily via caveolae-dependent mechanism promotes their use in targeting a broad spectrum of cancers

An Anillin-Ect2 Complex Stabilizes Central Spindle Microtubules at the Cortex during Cytokinesis

Cytokinesis occurs due to the RhoA-dependent ingression of an actomyosin ring. During anaphase, the Rho GEF (guanine nucleotide exchange factor) Ect2 is recruited to the central spindle via its interaction with MgcRacGAP/Cyk-4, and activates RhoA in the central plane of the cell. Ect2 also localizes to the cortex, where it has access to RhoA. The N-terminus of Ect2 binds to Cyk-4, and the C-terminus contains conserved DH (Dbl homologous) and PH (Pleckstrin Homology) domains with GEF activity. The PH domain is required for Ect2's cortical localization, but its molecular function is not known. In cultured human cells, we found that the PH domain interacts with anillin, a contractile ring protein that scaffolds actin and myosin and interacts with RhoA. The anillin-Ect2 interaction may require Ect2's association with lipids, since a novel mutation in the PH domain, which disrupts phospholipid association, weakens their interaction. An anillin-RacGAP50C (homologue of Cyk-4) complex was previously described in Drosophila, which may crosslink the central spindle to the cortex to stabilize the position of the contractile ring. Our data supports an analogous function for the anillin-Ect2 complex in human cells and one hypothesis is that this complex has functionally replaced the Drosophila anillin-RacGAP50C complex. Complexes between central spindle proteins and cortical proteins could regulate the position of the contractile ring by stabilizing microtubule-cortical interactions at the division plane to ensure the generation of active RhoA in a discrete zone

The role of the Rho-binding kinase/myosin phosphatase pathway in C. elegans embryogenesis

Bibliography: p. 194-22

Patterns of PKC53E protein expression in Drosophila melanogaster

Bibliography: p. 148-159

Cytokinetic diversity in mammalian cells is revealed by the characterization of endogenous anillin, Ect2 and RhoA

Cytokinesis is required to physically separate the daughter cells at the end of mitosis. This crucial process requires the assembly and ingression of an actomyosin ring, which must occur with high fidelity to avoid aneuploidy and cell fate changes. Most of our knowledge of mammalian cytokinesis was generated using over-expressed transgenes in HeLa cells. Over-expression can introduce artefacts, while HeLa are cancerous human cells that have lost their epithelial identity, and the mechanisms controlling cytokinesis in these cells could be vastly different from other cell types. Here, we tagged endogenous anillin, Ect2 and RhoA with mNeonGreen and characterized their localization during cytokinesis for the first time in live human cells. Comparing anillin localization in multiple cell types revealed cytokinetic diversity with differences in the duration and symmetry of ring closure, and the timing of cortical recruitment. Our findings show that the breadth of anillin correlates with the rate of ring closure, and support models where cell size or ploidy affects the cortical organization, and intrinsic mechanisms control the symmetry of ring closure. This work highlights the need to study cytokinesis in more diverse cell types, which will be facilitated by the reagents generated for this study

Supplementary video 5 from Cytokinetic diversity in mammalian cells is revealed by the characterization of endogenous anillin, Ect2 and RhoA

The video shows reconstruction of pancreatic BRIN-BD11 cells from the FIB/SEM data. The insulin secretory granules are coloured in green and the nucleus in red. ;The video shows reconstruction of pancreatic INS-1E cells from the FIB/SEM data. The insulin secretory granules are coloured in green and the nucleus in red. ;The video shows reconstruction of pancreatic MIN6 cells from the FIB/SEM data. The insulin secretory granules are coloured in green and the nucleus in red. ;Cryo-electron diffraction tomography tilt series, collected on the granule dense core, using discontinuous rotation between -40 ° and +40 ° with 2 ° steps.;Power spectra calculated from the cryo-electron tomography tilt series data, collected on the granule dense core. The sample was tilted between -40 ° and +40 ° with 2 ° increments

Supplementary video 1 from Cytokinetic diversity in mammalian cells is revealed by the characterization of endogenous anillin, Ect2 and RhoA

The video shows reconstruction of pancreatic BRIN-BD11 cells from the FIB/SEM data. The insulin secretory granules are coloured in green and the nucleus in red. ;The video shows reconstruction of pancreatic INS-1E cells from the FIB/SEM data. The insulin secretory granules are coloured in green and the nucleus in red. ;The video shows reconstruction of pancreatic MIN6 cells from the FIB/SEM data. The insulin secretory granules are coloured in green and the nucleus in red. ;Cryo-electron diffraction tomography tilt series, collected on the granule dense core, using discontinuous rotation between -40 ° and +40 ° with 2 ° steps.;Power spectra calculated from the cryo-electron tomography tilt series data, collected on the granule dense core. The sample was tilted between -40 ° and +40 ° with 2 ° increments

Supplementary video 2 from Cytokinetic diversity in mammalian cells is revealed by the characterization of endogenous anillin, Ect2 and RhoA

The video shows reconstruction of pancreatic BRIN-BD11 cells from the FIB/SEM data. The insulin secretory granules are coloured in green and the nucleus in red. ;The video shows reconstruction of pancreatic INS-1E cells from the FIB/SEM data. The insulin secretory granules are coloured in green and the nucleus in red. ;The video shows reconstruction of pancreatic MIN6 cells from the FIB/SEM data. The insulin secretory granules are coloured in green and the nucleus in red. ;Cryo-electron diffraction tomography tilt series, collected on the granule dense core, using discontinuous rotation between -40 ° and +40 ° with 2 ° steps.;Power spectra calculated from the cryo-electron tomography tilt series data, collected on the granule dense core. The sample was tilted between -40 ° and +40 ° with 2 ° increments