scholarly journals Microinjection of a monoclonal antibody against a 37-kD protein (tropomyosin 2) prevents the formation of new acetylcholine receptor clusters.

1989 ◽  
Vol 109 (5) ◽  
pp. 2337-2344 ◽  
Author(s):  
G Marazzi ◽  
F Bard ◽  
M W Klymkowsky ◽  
L L Rubin
Keyword(s):  
Monoclonal Antibody ◽  
Acetylcholine Receptor ◽  
Rous Sarcoma Virus ◽  
Acetylcholine Receptors ◽  
Neuromuscular Junctions ◽  
Muscle Cells ◽  
Rous Sarcoma ◽  
Sarcoma Virus ◽  
Receptor Clusters

We have shown previously that chick muscle cells transformed with Rous sarcoma virus are unable to form clusters of acetylcholine receptors (AChRs) (Anthony, D. T., S. M. Schuetze, and L. L. Rubin. 1984. Proc. Natl. Acad. Sci. USA. 81:2265-2269) and are missing a 37-KD tropomyosin-like protein (TM-2) (Anthony, D. T., R. J. Jacobs-Cohen, G. Marazzi, and L. L. Rubin. 1988. J. Cell Biol. 106:1713-1721). In an attempt to clarify the role of TM-2 in the formation and/or maintenance of AChR clusters, we have microinjected a monoclonal antibody specific for TM-2 (D3-16) into normal chick muscle cells in culture. D3-16 injection blocks the formation of new clusters but does not affect the preexisting ones. In addition, TM-2 is concentrated at rat neuromuscular junctions. These data suggest that TM-2 may play an important role in promoting the formation of AChR clusters.

Role of the mitogenic property and kinase activity of p60src in tumor formation by Rous sarcoma virus.

1984 ◽  
Vol 49 (2) ◽  
pp. 325-332 ◽  
Author(s):  
F Poirier ◽  
P Jullien ◽  
P Dezelee ◽  
G Dambrine ◽  
E Esnault ◽  
...  
Keyword(s):  
Rous Sarcoma Virus ◽  
Kinase Activity ◽  
Tumor Formation ◽  
Rous Sarcoma ◽  
Sarcoma Virus

scholarly journals Association of beta-cytoplasmic actin with high concentrations of acetylcholine receptor (AChR) in normal and anti-AChR-treated primary rat muscle cultures.

1984 ◽  
Vol 32 (9) ◽  
pp. 973-981 ◽  
Author(s):  
B W Lubit
Keyword(s):  
Acetylcholine Receptor ◽  
Acetylcholine Receptors ◽  
Neuromuscular Junctions ◽  
Morphological Changes ◽  
Muscle Cells ◽  
High Concentration ◽  
Rat Muscle ◽  
Cytoplasmic Actin ◽  
High Concentrations

Previous immunocytochemical studies in which an antibody specific for mammalian cytoplasmic actin was used showed that a high concentration of cytoplasmic actin exists at neuromuscular junctions of rat muscle fibers such that the distribution of actin corresponded exactly to that of the acetylcholine receptors. Although clusters of acetylcholine receptors also are present in noninnervated rat and chick muscle cells grown in vitro, neither the mechanism for the formation and maintenance of these clusters nor the relationship of these clusters to the high density of acetylcholine receptors at the neuromuscular junction in vivo are known. In the present study, a relationship between beta-cytoplasmic actin and acetylcholine receptors in vitro has been demonstrated immunocytochemically using an antibody specific for the beta-form of cytoplasmic actin. Networks of cytoplasmic actin-containing filaments were found in discrete regions of the myotube membrane that also contained high concentrations of acetylcholine receptors; such high concentrations of acetylcholine receptors have been described in regions of membrane-substrate contact. Moreover, when primary rat myotubes were exposed to human myasthenic serum, gross morphological changes, accompanied by an apparent rearrangement of the cytoplasmic actin-containing cytoskeleton, were produced. Although whether the distribution of cytoplasmic actin-containing structures was influenced by the organization of acetylcholine receptor or vice versa cannot be determined from these studies, these findings suggest that in primary rat muscle cells grown in vitro, acetylcholine receptors and beta-cytoplasmic actin-containing structures may be somehow connected.

The membrane skeleton of acetylcholine receptor domains in rat myotubes contains antiparallel homodimers of beta-spectrin in filaments quantitatively resembling those of erythrocytes

1995 ◽  
Vol 108 (9) ◽  
pp. 3145-3154 ◽  
Author(s):  
D.W. Pumplin
Keyword(s):  
Monoclonal Antibody ◽  
Acetylcholine Receptor ◽  
Acetylcholine Receptors ◽  
Cytoplasmic Membrane ◽  
Membrane Surface ◽  
Membrane Skeleton ◽  
Immunogold Labeling ◽  
Platinum Coating ◽  
High Concentrations ◽  
Receptor Clusters

I used immunogold labeling and quick-freeze, deep-etch, rotary replication to characterize the membrane skeleton at regions with high concentrations of acetylcholine receptor domains in receptor clusters of cultured rat muscle cells. This membrane skeleton consists of a network of filaments closely applied to the cytoplasmic membrane surface. The filaments are specifically decorated by immunogold labeling with a monoclonal antibody, VIIF7, that recognizes an isoform of beta-spectrin colocalizing with acetylcholine receptors. The filaments are 32 +/- 11 nm in length and three to four filaments (average 3.1-3.3) join at each intersection to form the network. These parameters are nearly identical to those reported previously for the membrane skeleton of erythrocytes. Depending on the amount of platinum coating, filament diameters range from 9 to 11 nm in diameter, and are 1.4 nm larger on average than spectrin filaments of erythrocytes replicated at the same time. Filaments are decorated with gold particles close to one end, consistent with the location of the epitope recognized by the monoclonal antibody. Computer modeling shows that all filament intersections in the membrane skeletal network are equally capable of being labeled by the monoclonal antibody. This pattern of labeling is consistent with a network containing antiparallel homodimers of beta-spectrin.

scholarly journals Role of p60src kinase activity in the induction of neuroretinal cell proliferation by rous sarcoma virus.

1982 ◽  
Vol 42 (3) ◽  
pp. 780-789 ◽  
Author(s):  
F Poirier ◽  
G Calothy ◽  
R E Karess ◽  
E Erikson ◽  
H Hanafusa
Keyword(s):  
Cell Proliferation ◽  
Rous Sarcoma Virus ◽  
Kinase Activity ◽  
Rous Sarcoma ◽  
Sarcoma Virus

scholarly journals Freeze-fracture and electrophysiological studies of newly developed acetylcholine receptors in Xenopus embryonic muscle cells.

1984 ◽  
Vol 98 (6) ◽  
pp. 2160-2173 ◽  
Author(s):  
P C Bridgman ◽  
S Nakajima ◽  
A S Greenberg ◽  
Y Nakajima
Keyword(s):  
Size Distribution ◽  
Acetylcholine Receptor ◽  
Acetylcholine Receptors ◽  
Freeze Fracture ◽  
Muscle Cells ◽  
Embryonic Muscle ◽  
Freeze Fracture Electron Microscopy ◽  
Receptor Clusters ◽  
Alpha Bungarotoxin ◽  
Solitary Form

The development of acetylcholine receptors on Xenopus embryonic muscle cells both in culture and in situ was studied using electrophysiology and freeze-fracture electron microscopy. Acetylcholine sensitivity first appeared at developmental stage 20 and gradually increased up to about stage 31. Freeze-fracture of muscle cells that were nonsensitive to acetylcholine revealed diffusely distributed small P-face intramembraneous particles. When cells acquired sensitivity to acetylcholine, a different group of diffusely distributed large P-face particles began to appear. This group of particles was analyzed by subtracting the size distribution found on nonsensitive cells from that found on sensitive cells. We call this group of particles difference particles. The sizes of difference particles were large (peak diameter 11 nm). The density of difference particles gradually increased with development. The density of small particles (less than 9 nm) did not change with development. At later stages (32-36) aggregates of large particles appeared, which probably represent acetylcholine receptor clusters. The size distribution of difference particles was close to that of the aggregated particles, suggesting that at least part of difference particles represent diffusely distributed acetylcholine receptors. Difference particles exist mostly in solitary form (occasionally double), indicating that an acetylcholine receptor can be functional in solitary form. This result also shows that diffuse acetylcholine receptors that have previously been observed with 125I-alpha-bungarotoxin autoradiography do indeed exist in solitary forms not as microaggregates.

scholarly journals Genetic Studies of the β-Hairpin Loop of Rous Sarcoma Virus Capsid Protein

2006 ◽  
Vol 81 (3) ◽  
pp. 1288-1296 ◽  
Author(s):  
Jared L. Spidel ◽  
Carol B. Wilson ◽  
Rebecca C. Craven ◽  
John W. Wills
Keyword(s):  
Binding Site ◽  
Rous Sarcoma Virus ◽  
Critical Role ◽  
Strong Support ◽  
Genome Replication ◽  
Consensus Binding Site ◽  
Rous Sarcoma ◽  
Capsid Shell ◽  
Sarcoma Virus

ABSTRACT The first few residues of the Rous sarcoma virus (RSV) CA protein comprise a structurally dynamic region that forms part of a Gag-Gag interface in immature virus particles. Dissociation of this interaction during maturation allows refolding and formation of a β-hairpin structure important for assembly of CA monomers into the mature capsid shell. A consensus binding site for the cellular Ubc9 protein was previously identified within this region, suggesting that binding of Ubc9 and subsequent small ubiquitin-like modifier protein 1 (SUMO-1) modification of CA may play a role either in regulating the assembly activity of CA in immature particles or mature cores or in controlling postentry function(s) during the establishment of infection. In the present study, mutations designed to eliminate the consensus binding site were used to dissect the potentially overlapping functions of these residues. The resulting replication defects could not be traced to a failure to form particles of normal composition but, rather, to a deficit in genome replication. Genetic suppressors of two detrimental β-hairpin mutations improved infectivity without restoring the consensus site or creating a novel one elsewhere. Optimal restoration of infectivity to a Lys-to-Arg mutant required a combination of secondary changes, one on the surface of each domain of CA. Rather than arguing for a critical role of Ubc9 and SUMO in RSV replication, these findings provide strong support for a structural role of the N-terminal residues and a particularly striking example of long-range interactions between regions of CA in achieving a functional core competent for genome replication.

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