Targeted disruption of genes for gp138, a cell-fusion-related protein in Dictyostelium discoideum, revealed the existence of a third gene

The dose response of Sendai virus-induced cell fusion was studied in 10 mammalian cell lines, comprising 5 continuous and 5 diploid cell lines originating from 5 species. The extent of fusion was calculated using a parameter directly proportional to the number of fusion events (t-parameter). At lower levels of fusion the dose response was found to be based on the same simple kinetic rules in all cell lines and was defined by the formula: t = FS. FAU/(I + FS. FAU), where FS (fusion sensitivity) is a cell-specific constant of the fusion rate and FAU (fusion activity units) is the virus dose. The FS potential of a cell line was determined as the linear regression coefficient of the fusion index (t/(I - t)) on the virus dose. At higher levels of fusion, when the fusion extent reached cell-line-specific maximal levels, the dose response was not as uniform. In general, and particularly in the cases of the diploid cell lines, these maximal levels were directly proportional to the FS potentials. Thus, it was concluded that the FS potential is the basic quantitative feature, which expresses the cellular fusion efficiency. The fact that FS varied extensively between cell lines, but at the same time apparently followed certain patterns (being higher in continuous compared to diploid cell lines and being related to the species of origin of the cells), emphasizes it biological significance as well as its possible usefulness in studies of the efficiency of various molecular interactions in the cell membrane/cytoskeleton system.

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Regulation of a ras-related protein during development of Dictyostelium discoideum

Molecular and Cellular Biology ◽

10.1128/mcb.5.1.33-39.1985 ◽

1985 ◽

Vol 5 (1) ◽

pp. 33-39

Author(s):

T Pawson ◽

T Amiel ◽

E Hinze ◽

N Auersperg ◽

N Neave ◽

...

Keyword(s):

Molecular Weight ◽

Dictyostelium Discoideum ◽

Dna Sequences ◽

Tryptic Peptide ◽

Related Protein ◽

Post Translational Modification ◽

Peptide Analysis ◽

Fruiting Body Formation ◽

Weight Protein ◽

Primary Gene

Recent work has shown that DNA sequences related to the mammalian ras proto-oncogenes are highly conserved in eucaryotic evolution. A monoclonal antibody (Y13-259) to mammalian p21ras specifically precipitated a 23,000-molecular-weight protein (p23) from lysates of Dictyostelium discoideum amoebae. Tryptic peptide analysis indicated that D. discoideum p23 was closely related in its primary structure to mammalian p21ras. p23 was apparently derived by post-translational modification of a 24,000-molecular-weight primary gene product. The amount of p23 was highest in growing amoebae, but declined markedly with the onset of differentiation such that by fruiting body formation there was less than 10% of the amoeboid level. The rate of p23 synthesis dropped rapidly during aggregation, rose transiently during pseudoplasmodial formation, and then declined during the terminal stages of differentiation. There was, therefore, a strong correlation between the expression of the ras-related protein p23 and cell proliferation of D. discoideum.

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Mapping of a cell-binding domain in the cell adhesion molecule gp80 of Dictyostelium discoideum.

The Journal of Cell Biology ◽

10.1083/jcb.107.5.1835 ◽

1988 ◽

Vol 107 (5) ◽

pp. 1835-1843 ◽

Cited By ~ 22

Author(s):

R K Kamboj ◽

L M Wong ◽

T Y Lam ◽

C H Siu

Keyword(s):

Cell Adhesion ◽

Dictyostelium Discoideum ◽

Fusion Proteins ◽

Binding Activity ◽

Binding Domain ◽

Globular Domain ◽

Cell Binding ◽

Homophilic Interaction ◽

A Cell ◽

Cell Binding Domain

At the aggregation stage of Dictyostelium discoideum development, a cell surface glycoprotein of Mr 80,000 (gp80) has been found to mediate the EDTA-resistant type of cell-cell adhesion via homophilic interaction (Siu, C.-H., A. Cho, and A. H. C. Choi. 1987. J. Cell Biol. 105:2523-2533). To investigate the structure-function relationships of gp80, we have isolated full length cDNA clones for gp80 and determined the DNA sequence. The deduced structure of gp80 showed three major domains. An amino-terminal globular domain composed of the bulk of the protein is supported by a short stalk region, which is followed by a membrane anchor at the carboxy terminus. Structural analysis suggested that the cell-binding domain of gp80 resides within the globular domain near the amino terminus. To investigate the relationship of the cell-binding activity to this region of the polypeptide, three protein A/gp80 (PA80) gene fusions were constructed using the expression vector pRIT2T. These PA80 fusion proteins were assayed for their ability to bind to aggregation stage cells. Binding of 125I-labeled fusion proteins PA80I (containing the Val123 to Ile514 fragment of gp80) and PA80II (Val123 to Ala258) was dosage dependent and could be inhibited by precoating cells with the cell cohesion-blocking mAb 80L5C4. On the other hand, there was no appreciable binding of PA80III (Ile174 to Ile514) to cells. Reassociation of cells was significantly inhibited in the presence of PA80I or PA80II. In addition, 125I-labeled PA80II exhibited homophilic interaction with immobilized PA80I, PA80II, or gp80. The results of these studies lead to the mapping of a cell-binding domain in the region between Val123 and Leu173 of gp80 and provide direct evidence that the cell-binding activity of gp80 resides in the protein moiety.

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Hypoxia triggers collective aerotactic migration in Dictyostelium discoideum

10.1101/2020.08.17.246082 ◽

2020 ◽

Author(s):

O. Cochet-Escartin ◽

M. Demircigil ◽

S. Hirose ◽

B. Allais ◽

P. Gonzalo ◽

...

Keyword(s):

Dictyostelium Discoideum ◽

Cell Communication ◽

Quantitative Agreement ◽

Cellular Potts Model ◽

Detection Mechanism ◽

Cell Behaviors ◽

Dense Ring ◽

Efficient Detection ◽

Technological Developments ◽

A Cell

AbstractIt is well known that eukaryotic cells can sense oxygen (O2) and adapt their metabolism accordingly. It is less known that they can also move towards regions of higher oxygen level (aerotaxis). Using a self-generated hypoxic assay, we show that the social amoeba Dictyostelium discoideum displays a spectacular aerotactic behavior. When a cell colony is covered by a coverglass, cells quickly consume the available O2 and the ones close to the periphery move directionally outward forming a dense ring keeping a constant speed and density. To confirm that O2 is the main molecular player in this seemingly collective process, we combined two technological developments, porphyrin based O2 sensing films and microfluidic O2 gradient generators. We showed that Dictyostelium cells exhibit aerotactic and aerokinetic (increased speed at low O2) response in an extremely low range of O2 concentration (0-1.5%) indicative of a very efficient detection mechanism. The various cell behaviors under self-generated or imposed O2 gradients were modeled with a very satisfactory quantitative agreement using an in silico cellular Potts model built on experimental observations. This computational model was complemented with a parsimonious ‘Go or Grow’ partial differential equation (PDE) model. In both models, we found that the collective migration of a dense ring can be explained by the interplay between cell division and the modulation of aerotaxis, without the need for cell-cell communication.

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