Regulatory signals affecting a selective loss of mRNA in Dictyostelium discoideum

1989 ◽  
Vol 94 (3) ◽  
pp. 501-509
Author(s):  
H.H. Hassanain ◽  
W. Kopachik
Keyword(s):  
Cyclic Amp ◽  
Cell Surface ◽  
Dictyostelium Discoideum ◽  
Transcript Level ◽  
Cell Surface Receptor ◽  
Cell Contact ◽  
Specific Cell ◽  
Mrna Levels ◽  
Stage Of Development ◽  
Surface Receptor

We identified signals that affect mRNA levels complementary to a gene that is highly expressed in vegetative Dictyostelium discoideum cells. This gene has been cloned as cDNA in the plasmid pcD-D2. The level of transcripts homologous to pcD-D2 fell dramatically in strain XP55 during the aggregation stage of development when cells differentiate on agar. The level, however, did not fall simply as a result of starvation or aggregation-specific cell contact. Rather, before the level is reduced cells must be deprived of amino acids and cyclic AMP administered in amounts and at intervals in pulses to mimic cyclic AMP signal-relay in aggregation. This effect can be blocked either with cyclic AMP-S (a non-hydrolysable cyclic AMP analogue) or adenosine, both of which prevent cyclic AMP binding to the cyclic AMP cell surface receptor. It is also blocked in ‘frigid’ aggregation-deficient mutants HC85 and HC112 known to be defective in a G alpha protein. We conclude that the transcript level is balanced by positive nutritional signals acting against negative signals transduced in part through a cell surface cyclic AMP receptor.

Pharmacological characterization of cyclic AMP receptors mediating gene regulation in Dictyostelium discoideum

1986 ◽  
Vol 6 (7) ◽  
pp. 2402-2408
Author(s):  
B Haribabu ◽  
R P Dottin
Keyword(s):  
Gene Expression ◽  
Cyclic Amp ◽  
Cell Surface ◽  
Dictyostelium Discoideum ◽  
Cell Surface Receptor ◽  
Intracellular Camp ◽  
Response Curves ◽  
Pharmacological Characterization ◽  
Surface Receptor ◽  
Extracellular Molecules

Extracellular molecules regulate gene expression in eucaryotes. Exogenous cyclic AMP (cAMP) affects the expression of a large number of developmentally regulated genes in Dictyostelium discoideum. Here, we determine the specificity of the receptor(s) which mediates gene expression by using analogs of cAMP. The order of potency with which these analogs affect the expression of specific genes is consistent with the specificity of their binding to a cell surface receptor and is distinct from their affinity for intracellular cAMP-dependent protein kinase. Dose-response curves with cAMP and adenosine 3',5'-monophosphorothioate, a nonhydrolyzable analog, revealed that the requirement for high concentrations of exogenous cAMP for regulating gene expression is due to the rapid degradation of cAMP by phosphodiesterase. The addition of low concentrations of cAMP (100 nM) or analogs in pulses also regulates gene expression. Both the genes that are positively regulated by exogenous cAMP and the discoidin gene, which is negatively regulated, respond to cAMP analogs to the same degree. Genes expressed in prespore or prestalk cells are also similarly regulated. These data suggest that the effects are mediated through the same receptor. The specificity of this receptor is indistinguishable from that of the well-characterized cell surface cAMP receptor.

scholarly journals Pharmacological characterization of cyclic AMP receptors mediating gene regulation in Dictyostelium discoideum.

1986 ◽  
Vol 6 (7) ◽  
pp. 2402-2408 ◽  
Author(s):  
B Haribabu ◽  
R P Dottin
Keyword(s):  
Gene Expression ◽  
Cyclic Amp ◽  
Cell Surface ◽  
Dictyostelium Discoideum ◽  
Cell Surface Receptor ◽  
Intracellular Camp ◽  
Response Curves ◽  
Pharmacological Characterization ◽  
Surface Receptor ◽  
Extracellular Molecules

Extracellular molecules regulate gene expression in eucaryotes. Exogenous cyclic AMP (cAMP) affects the expression of a large number of developmentally regulated genes in Dictyostelium discoideum. Here, we determine the specificity of the receptor(s) which mediates gene expression by using analogs of cAMP. The order of potency with which these analogs affect the expression of specific genes is consistent with the specificity of their binding to a cell surface receptor and is distinct from their affinity for intracellular cAMP-dependent protein kinase. Dose-response curves with cAMP and adenosine 3',5'-monophosphorothioate, a nonhydrolyzable analog, revealed that the requirement for high concentrations of exogenous cAMP for regulating gene expression is due to the rapid degradation of cAMP by phosphodiesterase. The addition of low concentrations of cAMP (100 nM) or analogs in pulses also regulates gene expression. Both the genes that are positively regulated by exogenous cAMP and the discoidin gene, which is negatively regulated, respond to cAMP analogs to the same degree. Genes expressed in prespore or prestalk cells are also similarly regulated. These data suggest that the effects are mediated through the same receptor. The specificity of this receptor is indistinguishable from that of the well-characterized cell surface cAMP receptor.

Inositol 1,4,5-trisphosphate and calcium stimulate actin polymerization in Dictyostelium discoideum

1986 ◽  
Vol 82 (1) ◽  
pp. 41-51
Author(s):  
G.N. Europe-Finner ◽  
P.C. Newell
Keyword(s):  
Cyclic Amp ◽  
Dictyostelium Discoideum ◽  
Actin Polymerization ◽  
Cell Surface Receptor ◽  
Receptor Stimulation ◽  
Normal Cells ◽  
Cellular Slime Mould ◽  
Inositol 1,4,5 Trisphosphate ◽  
Surface Receptor ◽  
Cellular Slime

The effect of chemoattractants such as cyclic AMP and folate on amoebae of the cellular slime mould Dictyostelium discoideum is to cause a series of rapid intracellular responses. One of the most rapid of these responses is the polymerization of actin associated with the cytoskeleton, an event correlated with pseudopodium formation, which occurs within 3–5 s of chemotactic receptor stimulation. We report that this response can be mimicked by addition of 5 microM-inositol 1,4,5-triphosphate (IP3) or by addition of 100 microM-Ca2+ to saponin-permeabilized amoebae. The data suggest that cytoskeletal actin polymerization occurs in normal cells as a result of IP3 formation in response to cell surface receptor stimulation and the consequent release of Ca2+ from internal stores.

scholarly journals Decreased urokinase receptor expression by overexpression of the plasminogen activator in a colon cancer cell line

1992 ◽  
Vol 285 (2) ◽  
pp. 629-634 ◽  
Author(s):  
W Hollas ◽  
E Soravia ◽  
A Mazar ◽  
J Henkin ◽  
F Blasi ◽  
...  
Keyword(s):  
Cell Surface ◽  
Binding Site ◽  
Cell Line ◽  
Marker Gene ◽  
Receptor Expression ◽  
Cell Surface Receptor ◽  
Scatchard Analysis ◽  
Specific Cell ◽  
Ample Evidence ◽  
Surface Receptor

There is now ample evidence that the proteolytic action of urokinase (UK) is potentiated by a specific cell surface receptor. The present study was undertaken to determine the role of UK as a modulator of its binding site. GEO colonic cells, which secrete low levels of UK (approximately 2.5 ng/ml per 72 h per 10(6) cells) and display approx. 10(4) receptors per cell, the majority of which are vacant, were transfected with an exogenous UK gene driven by the RSV long terminal repeat (LTR) promoter (pRSVUK). Several UK-overexpressing pRSVUK clones were identified by an e.l.i.s.a., Northern blotting and Southern blotting, and analysed for receptor numbers after an acid pretreatment which dissociates receptor-bound UK. pRSVUK GEO clones, expressing high levels of UK, consistently bound 50-75% less radioactive di-isopropylfluorophosphate (DFP)-UK than clones harbouring the selectable marker gene neo only or control GEO cells. Cross-linking experiments with a radioactive N-terminal fragment of UK which binds to the receptor showed a decreased amount of a binding protein of approx. 51 kDa in representative pRSVUK-transfected cells. Saturation and Scatchard analysis indicated that this reduction in radioligand binding reflected a 40-70% decrease in the number of UK receptors, rather than a change in the dissociation constant. The reduction in receptor display could be accounted for by a decrease in the amount of steady-state mRNA encoding the receptor. Radioactive DFP-UK binding to pRSVUK GEO clones, which display two-thirds less receptors than their neo counterparts, could be restored to control levels (untreated cells harbouring neo) by cultivating them in the presence of an antibody which inhibits the interaction of UK with its receptor. These data suggest that for one colonic cell line at least, UK reduces the expression of its own binding site via an autocrine stimulation of its cell surface receptor.

scholarly journals In vivo treatment with M8, a highly diluted tinctures complex, reduced the malignancy of a mouse melanoma model

2021 ◽  
Vol 10 (36) ◽  
pp. 142-144
Author(s):  
Lucas F De Andrade ◽  
Fernando SF Guimaraes ◽  
Gustavo Rossi ◽  
Rafael Zotz ◽  
Eneida J Da Lozzo ◽  
...  
Keyword(s):  
Hyaluronic Acid ◽  
Cell Surface ◽  
Metastatic Potential ◽  
Cell Surface Receptor ◽  
Specific Cell ◽  
Cd44 Expression ◽  
Mouse Melanoma ◽  
Conium Maculatum ◽  
Surface Receptor

Background: Cancer is a class of disease responsible for 13% of death cause worldwide. Among all types of cancers, one of the most aggressive and with the highest death rate is melanoma. It is highly metastatic and current treatments with chemotherapeutic drugs do not yield satisfactory results. Therefore, the interest on new therapeutics for cancer treatment has been increasing on research. Highly diluted tinctures (HDT) are intended to enhance immune system responses resulting in reduced frequency of various diseases, and often present no risk of serious side-effects due to its low toxicity. Previous results have demonstrated in vitro inhibition of invasion ability and in vivo anti-metastatic potential of B16F10 lung metastasis model after mice treatment with M8 inhalation. Aims: Now we have evaluated M8 effects on hyaluronic acid and its specific melanoma cell surface receptor (CD44) expression on lungs after inhalation by mice. Methodology: M8 compounds include Aconitum napellus 20dH, Arsenicum album 18dH, Asa foetida 20dH, Calcarea carbonica 16dH, Conium maculatum 17dH, Ipecacuanha 13dH, Phosphorus 20dH, Rhus toxicodendron 17H, Silicea 20dH, Sulphur 24dH, and Thuja occidentalis 19dH. B16F10 Melanoma cells were inoculated into C57B/L6 mouse lateral tail vein. Treatment started 24 hours after inoculation, and was repeated after each 12 hours during 14 days on an inhalation chamber that is adapted to little rodents. Mice were subjected to euthanasia by intraperitoneal injection of thiopental followed by decapitation. Lungs were surgically removed and analyzed under a stereomicroscope for the presence of metastatic foci. They were formaldehyde fixed, dehydrated and paraffin embedded. Histological sections were processed for hematoxilin/eosin (HE), Fontana-Masson and immunohistochemistry staining methods. Images were captured and blindly analysed by ImageJ (NIH) software. Results: HE and Fontana-Masson showed a reduction in number and size of metastatic nodules, as previously demonstrated. We have detected a reduction on hyaluronic acid as well as CD44 expression on mice lungs after M8 treatment. The high metastatic potential of melanoma is proportional to hyaluronic acid expression level, together with its specific cell surface receptor, the CD44. These results suggest that M8 treatment reduces malignancy of mouse melanoma through modulation of hyaluronic acid and CD44 expression, which play crucial roles in tumor invasion and growth. Conclusion: Even though further investigation are necessary to elucidate the mechanisms of action of M8 treatment there is an indication that these highly diluted tinctures could be a promising therapy to treat metastatic melanoma.

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