Effects of calcium antagonists on cyclic AMP phosphodiesterase induction in Dictyostelium discoideum

1987 ◽  
Vol 88 (3) ◽  
pp. 379-388
Author(s):  
M.B. Coukell ◽  
A.M. Cameron
Keyword(s):  
Cyclic Amp ◽  
Cell Viability ◽  
Dictyostelium Discoideum ◽  
Cyclic Gmp ◽  
Cell Shape ◽  
Second Messengers ◽  
Channel Blockers ◽  
Cyclic Amp Phosphodiesterase ◽  
Dose Dependent Fashion ◽  
Altered Cell

Previous studies have suggested that cyclic GMP and/or Ca2+ might function as second messengers in the induction by exogenous cyclic AMP of the cyclic AMP phosphodiesterase (PD) in Dictyostelium discoideum. To assess further the role of Ca2+ in PD induction we examined the effect on this process of a number of putative Ca2+-channel blockers. At relatively low micromolar concentrations, TMB-8, nicardipine, nifedipine, diltiazem and verapamil all altered cell shape and inhibited PD induction in a similar dose-dependent fashion. Concentrations of these drugs that abolished PD induction had no effect on cell viability; however, higher concentrations reduced viability and caused cell lysis. All effects of these compounds on the cells were antagonized at least partially by 5–10 mM-Ca2+. Other cations tested were considerably less effective. Like the organic inhibitors, La3+ also altered cell shape, inhibited PD induction and reduced cell viability at elevated concentrations, but its effect on the cells appeared to be more complex. Inhibition of PD induction by the organic antagonists could not be attributed solely to an impaired uptake of extracellular Ca2+, a reduction of ATP pools in the cells or a direct effect on calmodulin. Concentrations of TMB-8 that inhibited PD induction had little effect on the cyclic GMP response. Therefore, this compound did not inhibit PD induction indirectly by blocking cyclic GMP synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of suboptimal levels of extracellular calcium on the regulation of the cyclic AMP phosphodiesterase-inhibitor system and membrane differentiation in Dictyostelium discoideum

1988 ◽  
Vol 90 (4) ◽  
pp. 691-700 ◽  
Author(s):  
M.B. Coukell ◽  
A.M. Cameron
Keyword(s):  
Cyclic Amp ◽  
Dictyostelium Discoideum ◽  
Cyclic Gmp ◽  
Phosphodiesterase Inhibitor ◽  
Wild Type ◽  
Cyclic Amp Phosphodiesterase ◽  
Dose Dependent Fashion ◽  
Inhibitor System ◽  
Membrane Bound ◽  
Dose Dependent

When starved wild-type amoebae of Dictyostelium discoideum were washed and incubated in 1 mM-EGTA, their ability to induce soluble cyclic AMP phosphodiesterase (PD) activity in response to either millimolar cyclic AMP or a series of nanomolar cyclic AMP pulses was reduced by 55–75%. Supplementation of EGTA-treated cells with exogenous Ca2+ stimulated PD induction in a dose-dependent fashion (EC50 = 100–200 nM free extracellular Ca2+), and enzyme production was maximal at about 1 microM free Ca2+. Ca2+ depletion also strongly impaired production of the phosphodiesterase inhibitor (PDI). In contrast, other than delaying their appearance by about 1 h, EGTA had little effect on the induction by cyclic AMP pulses of cell surface markers such as contact sites A and membrane-bound PD activity. Similar changes in both the soluble and membrane activities were observed with strain NP368, a mutant that overproduces cyclic GMP when stimulated by cyclic AMP. Thus, Ca2+ depletion does not appear to inhibit PD and PDI production by reducing intracellular cyclic GMP. To determine whether Ca2+ depletion alters signal transduction, two mutants that produce the soluble PD activities constitutively were examined. Suboptimal concentrations of free extracellular Ca2+ were found to inhibit PD production in these cells to the same degree and with the same concentration dependence as low Ca2+ inhibited PD induction by cyclic AMP in wild-type cells. These results suggest that Ca2+ depletion by EGTA probably inhibits PD and PDI production indirectly by perturbing an intracellular Ca2+ pool(s) rather than by altering a surface cyclic AMP-receptor-mediated process.

scholarly journals Cyclic AMP and folic acid mediated cyclic GMP accumulation in Dictyostelium discoideum

FEBS Letters ◽  
1977 ◽  
Vol 79 (2) ◽  
pp. 331-336 ◽  
Author(s):  
José M. Mato ◽  
Peter J.M. Van Haastert ◽  
Frans A. Krens ◽  
Els H. Rhunsburger ◽  
Fred C.P.M. Dobbe ◽  
...  
Keyword(s):  
Folic Acid ◽  
Cyclic Amp ◽  
Dictyostelium Discoideum ◽  
Cyclic Gmp

Spike-shaped oscillations in the absence of measurable changes in cyclic AMP concentration in a mutant of Dictyostelium discoideum

1987 ◽  
Vol 87 (5) ◽  
pp. 723-730
Author(s):  
B. Wurster ◽  
R. Mohn
Keyword(s):  
Light Scattering ◽  
Cyclic Amp ◽  
Cell Surface ◽  
Dictyostelium Discoideum ◽  
Cyclic Gmp ◽  
Parent Strain ◽  
Reaction System ◽  
Cell Suspensions ◽  
Deficient Mutant ◽  
Cyclic Amp Synthesis

Periodic activities of Dictyostelium discoideum cells involve two types of oscillations, spike-shaped and sinusoidal. Spike-shaped oscillations are accompanied by the periodic synthesis and release of cyclic AMP, and cyclic AMP-activated cyclic AMP synthesis is believed to control these oscillations. Experiments described here call into question the importance of cyclic AMP in spike-shaped oscillations. Cell suspensions of strain agip43, an aggregation-deficient mutant of D. discoideum, displayed spike-shaped oscillations in light scattering with period lengths about 1.5 times larger than those of the parent strain. These oscillations were not accompanied by measurable oscillations of cyclic AMP and cyclic GMP. Applied cyclic AMP pulses elicited increases of two- to threefold in the cyclic AMP level and increases of seven- to ninefold in the cyclic GMP concentration. Cyclic AMP additions caused phase shifts in the oscillations of agip43 cells, suggesting that cyclic AMP receptors at the cell surface communicate with the oscillator. We interpret these results in terms of an oscillator not based on cyclic AMP. This oscillator should be coupled to the reaction system involving cyclic AMP synthesis and release. The latter can operate in an oscillatory manner in the parent strain Ax2 but not in mutant agip43.

The effects of inhibition of protein glycosylation on the aggregation of Dictyostelium discoideum

Development ◽  
1983 ◽  
Vol 78 (1) ◽  
pp. 229-248
Author(s):  
Charles John McDonald ◽  
Jeffrey Sampson
Keyword(s):  
Protein Synthesis ◽  
Cyclic Amp ◽  
Cell Surface ◽  
Dictyostelium Discoideum ◽  
Total Protein ◽  
Subsequent Development ◽  
Protein Glycosylation ◽  
Normal Process ◽  
Contact Sites ◽  
Cyclic Amp Phosphodiesterase

At concentrations greater than 10 µg ml−1 tunicamycin inhibited the incorporation of [3H]mannose into glycoproteins during the early phase of development in Dictyostelium discoideum, however, total protein synthesis was unaffected. Tunicamycin also interfered with the normal process of aggregation. In its presence small aggregates were observed at the time of normal aggregation, but amoebae failed to aggregate completely and subsequent development was inhibited. Inhibition of normal aggregation by tunicamycin was found to be reversible. The appearance of cell-associated and secreted cyclic AMP phosphodiesterase and cell-surface contact sites A was prevented by tunicamycin but cell surface cyclic AMP receptor activity developed normally in its presence. Tunicamycin also prevented amoebae from acquiring the ability to chemotact toward cyclic AMP. Addition of exogenous cyclic AMP phosphodiesterase restored the ability of amoebae to chemotact toward cyclic AMP in the presence of tunicamycin. Our data suggest that the primary block in aggregation caused by tunicamycin results from the inhibition of expression of active cyclic AMP phosphodiesterase.

scholarly journals A study on sensing and adaptation in Dictyostelium discoideum: guanosine 3',5'-phosphate accumulation and light-scattering responses.

1983 ◽  
Vol 96 (6) ◽  
pp. 1566-1570 ◽  
Author(s):  
B Wurster ◽  
U Butz
Keyword(s):  
Light Scattering ◽  
Cyclic Amp ◽  
Dictyostelium Discoideum ◽  
Cyclic Gmp ◽  
Rapid Decrease ◽  
Initial Increase ◽  
Steady State Concentration ◽  
Fast Reactions ◽  
State Concentration ◽  
Hydrolysis Of

Cells of Dictyostelium discoideum respond to extracellular cyclic AMP with marked changes in intracellular cyclic GMP levels and light scattering. In this work, defined temporal increases in cyclic AMP were produced by the continuous addition of cyclic AMP to agitated suspensions of cells; concomitant hydrolysis of cyclic AMP by the cells subsequently established a constant, steady state concentration. The cells responded to the initial increase in extracellular cyclic AMP with a rapid increase in the intracellular cyclic GMP concentration and a rapid decrease in light scattering. At cyclic AMP input rates of 0.5-5 nM X s-1, the fast reactions of cyclic GMP and light scattering had already relaxed while the cyclic AMP concentration in the cell suspension was still increasing. The cells responded to constant concentrations of cyclic AMP with constant elevated cyclic GMP concentrations and constant decreased levels of light scattering. Our results are consistent with the existence of two types of perception systems, one of which adapts to constant stimuli and one of which does not adapt.

scholarly journals Evidence for a messenger function of cyclic GMP during phosphodiesterase induction in Dictyostelium discoideum

1982 ◽  
Vol 152 (1) ◽  
pp. 232-238
Author(s):  
P J van Haastert ◽  
F J Pasveer ◽  
R C van der Meer ◽  
P R van der Heijden ◽  
H van Walsum ◽  
...  
Keyword(s):  
Computer Simulation ◽  
Folic Acid ◽  
Cyclic Amp ◽  
Dictyostelium Discoideum ◽  
Cyclic Gmp ◽  
Close Correlation ◽  
Phosphodiesterase Activity ◽  
Transient Elevation ◽  
Lines Of Evidence ◽  
Stimulation Of

Chemotactic stimulation of vegetative or aggregative Dictyostelium discoideum cells induced a transient elevation of cyclic GMP levels. The addition of chemoattractants to postvegetative cells by pulsing induced phosphodiesterase activity. The following lines of evidence suggest a messenger function for cyclic GMP in the induction of phosphodiesterase: (i) Folic acid and cyclic AMP increased cyclic GMP levels and induced phosphodiesterase activity. (ii) Cyclic AMP induced both cyclic GMP accumulation and phosphodiesterase activity by binding to a rate receptor. (iii) The effects of chemical modification of cyclic AMP or folic acid on cyclic GMP accumulation and phosphodiesterase induction were closely correlated. (iv) A close correlation existed between the increase of cyclic GMP levels and the amount of phosphodiesterase induced, independent of the type of chemoattractant by which this cyclic GMP accumulation was produced. (v) Computer simulation of cyclic GMP binding to intracellular cyclic GMP-binding proteins indicates that half-maximal occupation by cyclic GMP required the same chemoattractant concentration as did half-maximal phosphodiesterase induction.

scholarly journals Membrane-Bound Cyclic AMP Phosphodiesterase in Chemotactically Responding Cells of Dictyostelium discoideum

1972 ◽  
Vol 28 (1) ◽  
pp. 136-142 ◽  
Author(s):  
Dieter Malchow ◽  
Brigitte Nagele ◽  
Heinz Schwarz ◽  
Gunther Gerisch
Keyword(s):  
Cyclic Amp ◽  
Dictyostelium Discoideum ◽  
Cyclic Amp Phosphodiesterase ◽  
Membrane Bound
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