scholarly journals Computational model of polarized actin cables and cytokinetic actin ring formation in budding yeast

Cytoskeleton ◽  
2015 ◽  
Vol 72 (10) ◽  
pp. 517-533 ◽  
Author(s):  
Haosu Tang ◽  
Tamara C. Bidone ◽  
Dimitrios Vavylonis
Keyword(s):  
Computational Model ◽  
Budding Yeast ◽  
Ring Formation ◽  
Actin Ring ◽  
Actin Cables

Isolation and characterization of fission yeast mutants defective in the assembly and placement of the contractile actin ring

1996 ◽  
Vol 109 (1) ◽  
pp. 131-142 ◽  
Author(s):  
F. Chang ◽  
A. Woollard ◽  
P. Nurse
Keyword(s):  
Fission Yeast ◽  
Ring Formation ◽  
Cell Cycle Checkpoint ◽  
Yeast Cells ◽  
Temperature Sensitive ◽  
Actin Ring ◽  
Division Site ◽  
Isolation And Characterization ◽  
Cycle Checkpoint ◽  
Actin Cables

Fission yeast cells divide by medial cleavage using an actin-based contractile ring. We have conducted a genetic screen for temperature-sensitive mutants defective in the assembly and placement of this actin ring. Six genes necessary for actin ring formation and one gene necessary for placement of the actin ring have now been identified. The genes can be further organized into different phenotypic groups, suggesting that the gene products may have different functions in actin ring formation. Mutants of cdc3 and cdc8, which encode profilin and tropomyosin respectively, display disorganized actin patches in all cells. cdc12 and cdc15 mutants display disorganized actin patches during mitosis, but normal interphase actin patterns. cdc4 and rng2 mutants display disorganized actin cables during mitosis, but normal interphase actin patterns. In mid1 mutants, the actin ring and septum are positioned at random locations and angles on the cell surface, although the nucleus is positioned normally, indicating that the mid1 gene product is required to couple the division site to the position of the nucleus. mid1 mutant cells may reveal a new cell cycle checkpoint in telophase that coordinates cell division and the proper distribution of nuclei. The actin ring forms medially in a beta-tubulin mutant, showing that actin ring formation and placement are not dependent on the mitotic spindle.

F-actin ring formation and the role of F-actin cables in the fission yeastSchizosaccharomyces pombe

2002 ◽  
Vol 115 (5) ◽  
pp. 887-898 ◽  
Author(s):  
Ritsuko Arai ◽  
Issei Mabuchi
Keyword(s):  
Three Dimensional ◽  
Spindle Pole ◽  
Ring Formation ◽  
Restrictive Temperature ◽  
Permissive Temperature ◽  
Wild Type ◽  
Actin Ring ◽  
Medial Region ◽  
Dimensional Reconstruction ◽  
Actin Cables

Cells of the fission yeast Schizosaccharomyces pombe divide by the contraction of the F-actin ring formed at the medial region of the cell. We investigated the process of F-actin ring formation in detail using optical sectioning and three-dimensional reconstruction fluorescence microscopy. In wild-type cells, formation of an aster-like structure composed of F-actin cables and accumulation of F-actin cables were recognized at the medial cortex of the cell during prophase to metaphase. The formation of the aster-like structure seemed to initiate from branching of the longitudinal F-actin cables at a site near the spindle pole bodies, which had been duplicated but not yet separated. A single cable extended from the aster and encircled the cell at the equator to form a primary F-actin ring during metaphase. During anaphase,the accumulated F-actin cables were linked to the primary F-actin ring, and then all of these structures seemed to be packed to form the F-actin ring. These observations suggest that formation of the aster-like structure and the accumulation of the F-actin cables at the medial region of the cell during metaphase may be required to initiate the F-actin ring formation. In the nda3 mutant, which has a mutation in ß-tubulin and has been thought to be arrested at prophase, an F-actin ring with accumulated F-actin cables similar to that of anaphase wild-type cells was formed at a restrictive temperature. Immediately after shifting to a permissive temperature, this structure changed into a tightly packed ring. This suggests that the F-actin ring formation progresses beyond prophase in the nda3 cells once the cells enter prophase. We further examined F-actin structures in both cdc12 and cdc15 early cytokinesis mutants. As a result,Cdc12 seemed to be required for the primary F-actin ring formation during prophase, whereas Cdc15 may be involved in both packing the F-actin cables to form the F-actin ring and rearrangement of the F-actin after anaphase. In spg1, cdc7 and sid2 septum initiation mutants, the F-actin ring seemed to be formed in order.

scholarly journals Estrogen Decreases Cytoskeletal Organization by Forming an ERα/SHP2/c-Src Complex in Osteoclasts to Protect against Ovariectomy-Induced Bone Loss in Mice

Antioxidants ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 619
Author(s):  
Hyun-Jung Park ◽  
Malihatosadat Gholam-Zadeh ◽  
Sun-Young Yoon ◽  
Jae-Hee Suh ◽  
Hye-Seon Choi
Keyword(s):  
Bone Resorption ◽  
Bone Loss ◽  
Ring Formation ◽  
Tartrate Resistant Acid Phosphatase ◽  
Actin Ring ◽  
Collagen Crosslinks ◽  
Trap Staining ◽  
Src Activation

Loss of ovarian function is closely related to estrogen (E2) deficiency, which is responsible for increased osteoclast (OC) differentiation and activity. We aimed to investigate the action mechanism of E2 to decrease bone resorption in OCs to protect from ovariectomy (OVX)-induced bone loss in mice. In vivo, tartrate-resistant acid phosphatase (TRAP) staining in femur and serum carboxy-terminal collagen crosslinks-1 (CTX-1) were analyzed upon E2 injection after OVX in mice. In vitro, OCs were analyzed by TRAP staining, actin ring formation, carboxymethylation, determination of reactive oxygen species (ROS) level, and immunoprecipitation coupled with Western blot. In vivo and in vitro, E2 decreased OC size more dramatically than OC number and Methyl-piperidino-pyrazole hydrate dihydrochloride (MPPD), an estrogen receptor alpha (ERα) antagonist, augmented the OC size. ERα was found in plasma membranes and E2/ERα signaling affected receptor activator of nuclear factor κB ligand (RANKL)-induced actin ring formation by rapidly decreasing a proto-oncogene tyrosine-protein kinase, cellular sarcoma (c-Src) (Y416) phosphorylation in OCs. E2 exposure decreased physical interactions between NADPH oxidase 1 (NOX1) and the oxidized form of c-Src homology 2 (SH2)-containing protein tyrosine phosphatase 2 (SHP2), leading to higher levels of reduced SHP2. ERα formed a complex with the reduced form of SHP2 and c-Src to decrease c-Src activation upon E2 exposure, which blocked a signal for actin ring formation by decreased Vav guanine nucleotide exchange factor 3 (Vav3) (p–Y) and Ras-related C3 botulinum toxin substrate 1 (Rac1) (GTP) activation in OCs. E2/ERα signals consistently inhibited bone resorption in vitro. In conclusion, our study suggests that E2-binding to ERα forms a complex with SHP2/c-Src to attenuate c-Src activation that was induced upon RANKL stimulation in a non-genomic manner, resulting in an impaired actin ring formation and reducing bone resorption.

scholarly journals TNFα Potently Activates Osteoclasts, through a Direct Action Independent of and Strongly Synergistic with RANKL

Endocrinology ◽  
2002 ◽  
Vol 143 (3) ◽  
pp. 1108-1118 ◽  
Author(s):  
Karen Fuller ◽  
Chiho Murphy ◽  
Barrie Kirstein ◽  
Simon W. Fox ◽  
Timothy J. Chambers
Keyword(s):  
Direct Action ◽  
Ring Formation ◽  
Actin Ring ◽  
Independent Manner ◽  
Low Concentrations ◽  
Order Of Magnitude ◽  
Extreme Sensitivity ◽  
Osteoclastic Differentiation

Abstract TNFα is pivotal to the pathogenesis of inflammatory and possibly postmenopausal osteolysis. Much recent work has clarified mechanisms by which TNFα promotes osteoclastogenesis, but the means by which it activates osteoclasts to resorb bone remain uncertain. We found that very low concentrations of TNFα promoted actin ring formation, which correlates with functional activation in osteoclasts, both in osteoclasts formed in vitro and extracted from newborn rats. TNFα was equipotent with RANKL for this action. Activation by TNFα was unaffected by blockade of RANKL by OPG, its soluble decoy receptor, suggesting that this was due to a direct action on osteoclasts. Bone resorption was similarly directly and potently stimulated, in a RANKL-independent manner in osteoclasts, whether these were formed in vitro or in vivo. Interestingly, TNFα promoted actin ring formation at concentrations an order of magnitude below those required for osteoclastic differentiation. Moreover, TNFα strongly synergized with RANKL, such that miniscule concentrations of TNFα were sufficient to substantially augment osteoclast activation. The extreme sensitivity of osteoclasts to activation by TNFα suggests that the most sensitive osteolytic response of bone to TNFα is through activation of existing osteoclasts; and the strong synergy with RANKL provides a mechanism whereby increased osteolysis can be achieved without disturbance to the underlying pattern of osteoclastic localization.

Vps1, a recycling factor for the traffic from early endosome to the late Golgi

2013 ◽  
Vol 91 (6) ◽  
pp. 455-465 ◽  
Author(s):  
Joshua Lukehart ◽  
Chad Highfill ◽  
Kyoungtae Kim
Keyword(s):  
Cell Survival ◽  
Budding Yeast ◽  
Membrane Traffic ◽  
Early Endosome ◽  
Genetic Interactions ◽  
Cellular Membranes ◽  
Early Endosomes ◽  
Survival And Growth ◽  
Mild Defect ◽  
Actin Cables

Recycling of cellular membranes and their constituents plays a role for cell survival and growth. In the budding yeast, there are recycling traffics from early and late endosomal compartments to the late Golgi. Here, we examined a possible role for Vps1, a large GTPase, in the recycling traffic of GFP-Snc1 from early endosomes to the late Golgi. In the absence of Vps1 we observed an aberrant accumulation of GFP-Snc1 puncta in the cytoplasm that we identified as early endosomes. The N-terminal GTPase and the C-terminal GED domains of Vps1 are essential for Vps1’s function in Snc1 recycling. Our finding of genetic interactions of VPS1 with genes involved in early endosome-to-Golgi traffic further suggests Vps1 functions as a recycling factor in the membrane traffic. Finally, we provide evidence that the severe accumulation of GFP-Snc1 cytoplasmic puncta in vps1Δ cells is attributed to a mild defect in the retention of the GARP component Vps51 at the late Golgi, as well as a severe disruption of actin cables.

scholarly journals The Ligand for Osteoprotegerin (OPGL) Directly Activates Mature Osteoclasts

1999 ◽  
Vol 145 (3) ◽  
pp. 527-538 ◽  
Author(s):  
Teresa L. Burgess ◽  
Yi-xin Qian ◽  
Stephen Kaufman ◽  
Brian D. Ring ◽  
Gwyneth Van ◽  
...  
Keyword(s):  
Bone Resorption ◽  
Primary Cultures ◽  
Osteoclast Differentiation ◽  
Ring Formation ◽  
Surface Erosion ◽  
Direct Effects ◽  
Bone Surface ◽  
Actin Ring ◽  
Scanning Electron

Osteoprotegerin (OPG) and OPG-ligand (OPGL) potently inhibit and stimulate, respectively, osteoclast differentiation (Simonet, W.S., D.L. Lacey, C.R. Dunstan, M. Kelley, M.-S. Chang, R. Luethy, H.Q. Nguyen, S. Wooden, L. Bennett, T. Boone, et al. 1997. Cell. 89:309–319; Lacey, D.L., E. Timms, H.-L. Tan, M.J. Kelley, C.R. Dunstan, T. Burgess, R. Elliott, A. Colombero, G. Elliott, S. Scully, et al. 1998. Cell. 93: 165–176), but their effects on mature osteoclasts are not well understood. Using primary cultures of rat osteoclasts on bone slices, we find that OPGL causes approximately sevenfold increase in total bone surface erosion. By scanning electron microscopy, OPGL-treated osteoclasts generate more clusters of lacunae on bone suggesting that multiple, spatially associated cycles of resorption have occurred. However, the size of individual resorption events are unchanged by OPGL treatment. Mechanistically, OPGL binds specifically to mature OCs and rapidly (within 30 min) induces actin ring formation; a marked cytoskeletal rearrangement that necessarily precedes bone resorption. Furthermore, we show that antibodies raised against the OPGL receptor, RANK, also induce actin ring formation. OPGL-treated mice exhibit increases in blood ionized Ca++ within 1 h after injections, consistent with immediate OC activation in vivo. Finally, we find that OPG blocks OPGL's effects on both actin ring formation and bone resorption. Together, these findings indicate that, in addition to their effects on OC precursors, OPGL and OPG have profound and direct effects on mature OCs and indicate that the OC receptor, RANK, mediates OPGL's effects.

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