scholarly journals Interactions of actin, myosin, and an actin-binding protein of rabbit pulmonary macrophages. III. Effects of cytochalasin B.

1976 ◽  
Vol 71 (1) ◽  
pp. 295-303 ◽  
Author(s):  
J H Hartwig ◽  
T P Stossel
Keyword(s):  
Actin Filaments ◽  
Cytochalasin B ◽  
Binding Protein ◽  
Actin Binding ◽  
Gel Formation ◽  
Temperature Dependent ◽  
Actin Binding Protein ◽  
Low Concentrations ◽  
Pulmonary Macrophages

Low concentrations (greater than or equal to 10(-7) M) of cytochalasin B reversibly inhibit the temperature-dependent gelation of actin by an actin-binding protein. The cytochalasin B concentrations which maximally inhibit actin gel formation are 10-fold lower than the concentrations which maximally impair phagocytosis by intact macrophages. Cytochalasin B also prevents the polymerization of monomeric actin in sucrose extracts of macrophages in the absence but not the presence of 0.1 M CKl. 10(-6) M cytochalasin B dissolves macrophage extract gels and gels comprised of purified actin and actin-binding protein by dissociating actin-binding protein from actin filaments. This concentration of cytochalasin B, however, does not depolymerize the actin filatments.

scholarly journals Interactions of actin, myosin, and a new actin-binding protein of rabbit pulmonary macrophages. II. Role in cytoplasmic movement and phagocytosis.

1976 ◽  
Vol 68 (3) ◽  
pp. 602-619 ◽  
Author(s):  
T P Stossel ◽  
J H Hartwig
Keyword(s):  
Molecular Weight ◽  
Atpase Activity ◽  
Actin Filaments ◽  
Sucrose Solution ◽  
Binding Protein ◽  
Cooperative Interaction ◽  
Actin Binding ◽  
Temperature Dependent ◽  
Actin Binding Protein ◽  
Pulmonary Macrophages

Actin and myosin of rabbit pulmonary macrophages are influenced by two other proteins. A protein cofactor is required for the actin activation of macrophage myosin Mg2 ATPase activity, and a high molecular weight actin-binding protein aggregates actin filaments (Stossel T.P., and J.H. Hartwig. 1975. J. Biol. Chem. 250:5706-5711)9 When warmed in 0.34 M sucrose solution containing Mg2-ATP and dithiothreitol, these four proteins interact cooperatively. Acin-binding protein in the presence of actin causes the actin to form a gel, which liquifies when cooled. The myosin contracts the gel into an aggregate, and the rate of aggregation is accelerated by the cofactor. Therefore, we believe that these four proteins also effec the temperature-dependent gelation and aggregation of crude sucrose extracts pulmonary macrophages containing Mg2-ATP and dithiothreitol. The gelled extracts are composed of tangled filaments. Relative to homogenates of resting macrophages, the distribution of actin-binding protein in homogenates of phagocytizing macrophages is altered such that 2-6 times more actin-binding protein is soluble. Sucrose extracts of phagocytizing macrophages gel more rapidly than extracts of resting macrophages. Phagocytosis by pulmonary macrophages involves the formation of peripheral pseudopods containing filaments. The findings suggest that the actin-binding protein initiates a cooperative interaction of contractile proteins to generate cytoplasmic gelation, and that phagocytosis influences the behavior of the actin-binding protein.

Binding of Human Platelet Glycoprotein lb and Actin to Fragments of Actin-Binding Protein

1992 ◽  
Vol 67 (02) ◽  
pp. 252-257 ◽  
Author(s):  
Anne M Aakhus ◽  
J Michael Wilkinson ◽  
Nils Olav Solum
Keyword(s):  
Actin Filaments ◽  
High Speed ◽  
Binding Protein ◽  
Protein A ◽  
Actin Binding ◽  
Platelet Glycoprotein ◽  
Actin Binding Protein ◽  
Crossed Immunoelectrophoresis ◽  
Triton X ◽  
Calpain Inhibitors

SummaryActin-binding protein (ABP) is degraded into fragments of 190 and 90 kDa by calpain. A monoclonal antibody (MAb TI10) against the 90 kDa fragment of ABP coprecipitated with the glycoprotein lb (GP lb) peak observed on crossed immunoelectrophoresis of Triton X-100 extracts of platelets prepared without calpain inhibitors. MAb PM6/317 against the 190 kDa fragment was not coprecipitated with the GP lb peak under such conditions. The 90 kDa fragment was adsorbed on protein A agarose from extracts that had been preincubated with antibodies to GP lb. This supports the idea that the GP Ib-ABP interaction resides in the 90 kDa region of ABP. GP lb was sedimented with the Triton-insoluble actin filaments in trace amounts only, and only after high speed centrifugation (100,000 × g, 3 h). Both the 190 kDa and the 90 kDa fragments of ABP were sedimented with the Triton-insoluble actin filaments.

scholarly journals Actin-binding protein promotes the bipolar and perpendicular branching of actin filaments.

1980 ◽  
Vol 87 (3) ◽  
pp. 841-848 ◽  
Author(s):  
J H Hartwig ◽  
J Tyler ◽  
T P Stossel
Keyword(s):  
Actin Filaments ◽  
Actin Polymerization ◽  
Average Length ◽  
Binding Protein ◽  
Actin Binding ◽  
Branch Points ◽  
Heavy Meromyosin ◽  
Actin Binding Protein ◽  
Protein Dimers ◽  
Protein Molecules

Branching filaments with striking perpendicularity form when actin polymerizes in the presence of macrophage actin-binding protein. Actin-binding protein molecules are visible at the branch points. Compared with actin polymerized in the absence of actin-binding proteins, not only do the filaments branch but the average length of the actin filaments decreases from 3.2 to 0.63 micrometer. Arrowhead complexes formed by addition of heavy meromyosin molecules to the branching actin filaments point toward the branch points. Actin-binding protein also accelerates the onset of actin polymerization. All of these findings show that actin filaments assemble from nucleating sites on actin-binding protein dimers. A branching polymerization of actin filaments from a preexisting lattice of actin filaments joined by actin-binding protein molecules could generate expansion of cortical cytoplasm in amoeboid cells.

scholarly journals Three-dimensional structure of actin filaments and of an actin gel made with actin-binding protein.

1983 ◽  
Vol 96 (5) ◽  
pp. 1400-1413 ◽  
Author(s):  
R Niederman ◽  
P C Amrein ◽  
J Hartwig
Keyword(s):  
Actin Filaments ◽  
Binding Protein ◽  
Three Dimensional ◽  
Actin Binding ◽  
Dimensional Structure ◽  
Molar Ratio ◽  
Computer Assisted ◽  
Three Dimensional Structure ◽  
Actin Binding Protein ◽  
Critical Point Drying

Purified muscle actin and mixtures of actin and actin-binding protein were examined in the transmission electron microscope after fixation, critical point drying, and rotary shadowing. The three-dimensional structure of the protein assemblies was analyzed by a computer-assisted graphic analysis applicable to generalized filament networks. This analysis yielded information concerning the frequency of filament intersections, the filament length between these intersections, the angle at which filaments branch at these intersections, and the concentration of filaments within a defined volume. Purified actin at a concentration of 1 mg/ml assembled into a uniform mass of long filaments which overlap at random angles between 0 degrees and 90 degrees. Actin in the presence of macrophage actin-binding protein assembled into short, straight filaments, organized in a perpendicular branching network. The distance between branch points was inversely related to the molar ratio of actin-binding protein to actin. This distance was what would be predicted if actin filaments grew at right angles off of nucleation sites on the two ends of actin-binding protein dimers, and then annealed. The results suggest that actin in combination with actin-binding protein self-assembles to form a three-dimensional network resembling the peripheral cytoskeleton of motile cells.

scholarly journals Effect of actin-binding protein on the sedimentation properties of actin.

1982 ◽  
Vol 94 (1) ◽  
pp. 51-55 ◽  
Author(s):  
S Rosenberg ◽  
A Stracher
Keyword(s):  
Actin Filaments ◽  
Human Platelet ◽  
Binding Protein ◽  
Actin Binding ◽  
Cross Linking ◽  
Actin Binding Protein ◽  
Cell Biol

Actin and actin-binding protein (ABP) have recently been purified from human platelet cytoskeletons (S. Rosenberg, A. Stracher, and R.C. Lucas, 1981, J. Cell Biol. 91:201-211). Here, the effect of ABP on the sedimentation of actin was studied. When ABP was added to preformed F-actin filaments, it bound until a maximum ratio of 1:9 (ABP:actin, mol:mol) was reached. however, when actin was polymerized in the presence of ABP, two and a half times more ABP was able to bind to the actin- that is, every 3.4 actin monomers were now bound by an ABP dimer. ABP was not able to induce the sedimentation of actin under nonpolymerizing conditions but was able to reduce the time and concentration of actin required for sedimentation under slow polymerizing conditions. ABP, therefore, exerts its effect of G-actin by either nucleating polymerization or by cross-linking newly formed oligomers into a more sedimentable form.

scholarly journals The Plant-Specific Actin Binding Protein SCAB1 Stabilizes Actin Filaments and Regulates Stomatal Movement in Arabidopsis

2011 ◽  
Vol 23 (6) ◽  
pp. 2314-2330 ◽  
Author(s):  
Yang Zhao ◽  
Shuangshuang Zhao ◽  
Tonglin Mao ◽  
Xiaolu Qu ◽  
Wanhong Cao ◽  
...  
Keyword(s):  
Actin Filaments ◽  
Binding Protein ◽  
Actin Binding ◽  
Stomatal Movement ◽  
Actin Binding Protein

scholarly journals Identification of membrane proteins mediating the interaction of human platelets

1980 ◽  
Vol 86 (1) ◽  
pp. 77-86 ◽  
Author(s):  
D Phillips ◽  
L Jennings ◽  
H Edwards
Keyword(s):  
Actin Filaments ◽  
Binding Protein ◽  
Membrane Surface ◽  
Direct Interaction ◽  
Cytoskeletal Proteins ◽  
Actin Binding ◽  
Insoluble Residue ◽  
Membrane Glycoproteins ◽  
Actin Binding Protein ◽  
Activated Platelets

Membrane glycoproteins that mediate platelet-platelet interactions were investigated by identifying those associated with the cytoskeletal structures from aggregated platelets. The cytoskeletal structures from washed platelets, thrombin-activated platelets (platelets incubated with thrombin in the presence of mM EDTA to prevent aggregation) and thrombin- aggregated platelets (platelets activated in the presence of mM Ca(++) were prepared by first treating platelet suspensions with 1 percent Triton X-100 and 5 mM EGTA and then isolating the insoluble residue by centrifugation. The readily identifiable structures in electron micrographs of the residue from washed platelets had the shape and dimensions of actin filaments. Analysis of this residue from washed platelets had the shape and dimensions of actin filaments. Analysis of this residue by SDS gel electrophoresis showed that it consisted primarily of three proteins: actin (mol wt = 43,000), myosin (mol wt = 200,000) and a high molecular weight polypeptide (mol wt = 255,000) which had properties indentical to actin-binding protein (filamin). When platelets are activated with thrombin in the presence of EDTA to prevent aggregation, there was a marked increase in the amount of insoluble precipitate in the subsequent Triton extraction. Transmission electron microscopy showed that this residue not only contained the random array of actin filaments as seen above, but also organized structures from individual platelets which appeared as balls of electron-dense filamentous material approximately 1mum in diameter. SDS polyacrylamide gel analysis of the Triton residue of activated platelets showed that this preparation contained more actin, myosin and actin-binding protein than that from washed platelets plus polypeptides with mol wt of 56,000 and 90,000 and other minor polypeptides. Thus, thrombin activation appeared to increase polymerization of actin in association with other cytoskeletal proteins into structures that are observable after Triton extraction. The cytoskeletal structures from thrombin-aggregated platelets were similar to those from thrombin-activated platelets, except that the structural elements from individual platelets remained aggregated rather than randomly dispersed in the actin filaments. This suggested that the membrane components that mediate the direct interaction of platelets were in Triton residue from aggregated platelets. Only a small percentage of the membrane surface proteins and glycoproteins were found in the cytoskeletal structures from either washed platelets or thrombin-activated platelets. In contrast, the aggregated cytoskeletal structures from thrombin-aggregated platelets contained membrane glycoproteins IIb (26 percent of the total in pre-extracted platelets) and III (14 percent), suggesting that one or both of these glycoproteins participate in the direct interaction of platelets during aggregation.

scholarly journals ArabidopsisCROLIN1, a Novel Plant Actin-binding Protein, Functions in Cross-linking and Stabilizing Actin Filaments

2013 ◽  
Vol 288 (45) ◽  
pp. 32277-32288 ◽  
Author(s):  
Honglei Jia ◽  
Jisheng Li ◽  
Jingen Zhu ◽  
Tingting Fan ◽  
Dong Qian ◽  
...  
Keyword(s):  
Actin Filaments ◽  
Binding Protein ◽  
Actin Binding ◽  
Cross Linking ◽  
Actin Binding Protein ◽  
Protein Functions

scholarly journals Microtubule-associated Protein 2c Reorganizes Both Microtubules and Microfilaments into Distinct Cytological Structures in an Actin-binding Protein-280–deficient Melanoma Cell Line

1997 ◽  
Vol 136 (4) ◽  
pp. 845-857 ◽  
Author(s):  
C. Casey Cunningham ◽  
Nicole Leclerc ◽  
Lisa A. Flanagan ◽  
Mei Lu ◽  
Paul A. Janmey ◽  
...  
Keyword(s):  
Melanoma Cell ◽  
Binding Protein ◽  
Growth Cones ◽  
Actin Binding ◽  
Actin Binding Protein ◽  
Low Concentrations ◽  
Rheologic Property ◽  
Neuronal Growth Cones

The emergence of processes from cells often involves interactions between microtubules and microfilaments. Interactions between these two cytoskeletal systems are particularly apparent in neuronal growth cones. The juvenile isoform of the neuronal microtubule-associated protein 2 (MAP2c) is present in growth cones, where we hypothesize it mediates interactions between microfilaments and microtubules. To approach this problem in vivo, we used the human melanoma cell, M2, which lacks actin-binding protein-280 (ABP-280) and forms membrane blebs, which are not seen in wild-type or ABP-transfected cells. The microinjection of tau or mature MAP2 rescued the blebbing phenotype; MAP2c not only caused cessation of blebbing but also induced the formation of two distinct cellular structures. These were actin-rich lamellae, which often included membrane ruffles, and microtubule-bearing processes. The lamellae collapsed after treatment with cytochalasin D, and the processes retracted after treatment with colchicine. MAP2c was immunocytochemically visualized in zones of the cell that were devoid of tubulin, such as regions within the lamellae and in association with membrane ruffles. In vitro rheometry confirmed that MAP2c is an efficient actin gelation protein capable of organizing actin filaments into an isotropic array at very low concentrations; tau and mature MAP2 do not share this rheologic property. These results suggest that MAP2c engages in functionally specific interactions not only with microtubules but also with microfilaments.

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