Signal transduction and motility of Dictyostelium

1995 ◽  
Vol 15 (6) ◽  
pp. 445-462 ◽  
Author(s):  
Peter C. Newell
Keyword(s):  
Signal Transduction ◽  
Cyclic Amp ◽  
Cell Surface ◽  
Structural Gene ◽  
Light Chain ◽  
Cyclic Gmp ◽  
Myosin Ii ◽  
Cell Movement ◽  
Primary Defect

This review is concerned with the roles of cyclic GMP and Ca2+ ions in signal transduction for chemotaxis of Dictyostelium. These molecules are involved in signalling between the cell surface cyclic AMP receptors and cytoskeletal myosin II involved in chemotactic cell movement. Evidence is presented for uptake and/or eflux of Ca2+ being regulated by cyclic GMP. The link between Ca2+, cyclic GMP and chemotactic cell movement has been explored using “streamer F” mutants whose primary defect is in the structural gene for the cyclic GMP-specific phosphodiesterase. This mutation causes the mutants to produce an abnormally prolonged peak of cyclic GMP accumulation in response to stimulation with the chemoattractant cyclic AMP. The production and relay of cyclic AMP signals is normal in these mutants, but certain events associated with movement are (like the cyclic GMP response) abnormally prolonged in the mutants. These events include Ca2+ uptake, myosin II association with the cytoskeleton and regulation of both myosin heavy and light chain phosphorylation. These changes can be correlated with changes in the shape of the amoebae after chemotactic stimulation. Other mutants in which the accumulation of cyclic GMP in response to cyclic AMP stimulation was absent produced no myosin II responses.A model is described in which cyclic GMP (directly or indirectly via Ca2+) regulates accumulation of myosin II on the cytoskeleton by regulating phosphorylation of the myosin heavy and light chain kinases.

Regulation of myosin regulatory light chain phosphorylation via cyclic GMP during chemotaxis of Dictyostelium

1994 ◽  
Vol 107 (7) ◽  
pp. 1737-1743 ◽  
Author(s):  
G. Liu ◽  
P.C. Newell
Keyword(s):  
Cyclic Amp ◽  
Light Chain ◽  
Cyclic Gmp ◽  
Myosin Ii ◽  
Regulatory Light Chain ◽  
Published Data ◽  
Myosin Regulatory Light Chain ◽  
Control Strain ◽  
Regulatory Light Chain Phosphorylation ◽  
Stimulation Of

Previous studies on the chemotactic movement of Dictyostelium have indicated a role for cyclic GMP in regulating the association of myosin II with the cytoskeleton. In this study we have examined the part played by phosphorylation of the 18 kDa myosin regulatory light chain in this event. Using streamer F mutant NP368 (which is deficient in the structural gene for cyclic GMP-specific phosphodiesterase) we find that, for the regulatory light chain kinase, the major peak of phosphorylation is delayed compared to the parental control strain XP55, occurring at 80 seconds rather than about 30 seconds in XP55. In two independently derived mutants that are unable to increase their cellular concentration of cyclic GMP (above basal levels) in response to a chemotactic stimulus of cyclic AMP (KI-10 and SA219), no increase in the phosphorylation of the light chain occurred, or movement of myosin II to the cytoskeleton. We also find a smaller peak of light chain phosphorylation that occurs within 10 seconds of cyclic AMP stimulation of the amoebae, and which is absent in the cyclic GMP-unresponsive strains. We conclude that cyclic GMP is involved in regulating light chain phosphorylation in this system. The possible significance of these findings is discussed and a model that relates these findings to published data on cytoskeletal myosin changes during chemotaxis is presented.

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.

scholarly journals Evidence for the involvement of cyclic AMP in the pheromonal modulation of barnacle settlement

1995 ◽  
Vol 198 (3) ◽  
pp. 655-664 ◽  
Author(s):  
A Clare ◽  
R Thomas ◽  
D Rittschof
Keyword(s):  
Signal Transduction ◽  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Cyclic Gmp ◽  
Phosphodiesterase Inhibitor ◽  
Balanus Amphitrite ◽  
Dibutyryl Cyclic Amp ◽  
Physico Chemical ◽  
Miconazole Nitrate

The involvement of cyclic AMP in the settlement of the cypris larva of Balanus amphitrite amphitrite Darwin has been examined through the use of compounds that affect intracellular cyclic AMP levels. The activation of adenylate cyclase with forskolin, and the inhibition of phosphodiesterase with 3-isobutyl-1-methylxanthine, caffeine and theophylline, significantly increased the settlement of cyprids. Although the analogue dibutyryl cyclic AMP appeared to increase settlement, the effect was not significant. No marked increase in settlement resulted from the incubation of cyprids with dibutyryl cyclic GMP, 8-(4-chlorophenylthio) (CPT) cyclic AMP or papaverine (a phosphodiesterase inhibitor). Miconazole nitrate, an adenylate cyclase inhibitor, prevented settlement, but this effect appeared to be physico-chemical rather than pharmacological. Radioimmunoassay did not clearly show whether cyclic AMP levels changed following exposure of cyprids to a pulse of crude barnacle extract. However, exposure to forskolin significantly increased the cyclic AMP titre of cyprids. We conclude that compounds that alter intracellular cyclic AMP levels alter normal patterns of cyprid settlement. Whether this is because of an alteration in signal transduction is unclear.

scholarly journals Cyclic nucleotides in glutamate chemosensory signal transduction of Paramecium

1997 ◽  
Vol 110 (20) ◽  
pp. 2567-2572
Author(s):  
W.Q. Yang ◽  
C. Braun ◽  
H. Plattner ◽  
J. Purvee ◽  
J.L. Van Houten
Keyword(s):  
Signal Transduction ◽  
Cyclic Amp ◽  
Cyclic Gmp ◽  
Signal Transduction Pathway ◽  
Protein Kinase Inhibitors ◽  
Intracellular Camp ◽  
Paramecium Tetraurelia ◽  
Transduction Pathway ◽  
Kinetic Measurements ◽  
Chemosensory Transduction

Glutamate is an attractant stimulus to Paramecium tetraurelia. It causes a hyperpolarization of the cell and smooth, relatively fast swimming that is characteristic of hyperpolarizing stimuli. We show here that by 1–30 seconds of stimulation, glutamate increases intracellular cAMP. Interestingly, other attractant stimuli, such as acetate and NH4Cl, that similarly hyperpolarize the cell do not induce an increase in cyclic AMP observable at 30 seconds. In order to determine whether the changes in cyclic AMP could be rapid enough to participate in stimulation as compared to slower processes such as adaptation, rapid kinetic measurements of cyclic AMP were made on whole cells by quenched-flow. We found that, in cells stimulated with glutamate, intracellular cyclic AMP increases by 30 mseconds and peaks at about sevenfold over basal levels by 200 mseconds. Cyclic GMP does not change relative to basal levels over rapid or slower time courses of glutamate stimulation. An antagonist of glutamate, IMP, depolarizes the cells and decreases intracellular cyclic AMP by approx. 50% and slightly increases cyclic GMP. Results of behavioral tests of cells treated with protein kinase inhibitors also suggest that cyclic AMP is part of the signal transduction pathway for glutamate, but not for other attractant stimuli. These studies are the first demonstration of a possible role for cyclic nucleotide second messengers in an attractant chemosensory transduction pathway in Paramecium.

The role of cyclic GMP in regulating myosin during chemotaxis of Dictyostelium: evidence from a mutant lacking the normal cyclic GMP response to cyclic AMP

1993 ◽  
Vol 106 (2) ◽  
pp. 591-595 ◽  
Author(s):  
G. Liu ◽  
H. Kuwayama ◽  
S. Ishida ◽  
P.C. Newell
Keyword(s):  
Cyclic Amp ◽  
Heavy Chain ◽  
Cyclic Gmp ◽  
Parental Strain ◽  
Response Curve ◽  
Myosin Ii ◽  
Cellular Slime ◽  
Mutant Cells ◽  
Slight Displacement

Evidence has previously been reported that, during chemotaxis of the cellular slime mould Dictyostelium discoideum, cyclic GMP regulates the association of myosin II with the cytoskeleton and that this regulation is effected by inhibiting myosin II heavy chain phosphorylation (Liu and Newell, J. Cell Sci., 90, 123–129, 1988; 98, 483–490, 1991). Here we provide further evidence in support of this hypothesis using a mutant (KI-10) that is defective in chemotaxis and lacks the normal cyclic AMP-induced cyclic GMP response. We found that the cyclic AMP-induced cytoskeletal actin response was similar to that of the parental strain in this mutant (although showing a slight displacement in the dose-response curve) but the cytoskeletal myosin II heavy chain response was abolished. Moreover, the mutant showed no phosphorylation of myosin II heavy chain in response to cyclic AMP. Compared to the parental strain XP55, the mutant cells contained approximately 40% more protein and their doubling time was 30% longer. These differences could be due to differences in the efficiency of cell division, a process in which the proper regulation of myosin function is essential and in which cyclic GMP may therefore play a role.

scholarly journals Attractant-induced changes and oscillations of the extracellular Ca++ concentration in suspensions of differentiating Dictyostelium cells.

1984 ◽  
Vol 98 (1) ◽  
pp. 173-178 ◽  
Author(s):  
J Bumann ◽  
B Wurster ◽  
D Malchow
Keyword(s):  
Folic Acid ◽  
Cyclic Amp ◽  
Cell Surface ◽  
Cyclic Gmp ◽  
Time Course ◽  
Constant Stimulus ◽  
Surface Receptors ◽  
Induced Changes ◽  
Sensitive Electrode

We used a Ca++-sensitive electrode to measure changes in extracellular Ca++ concentration in cell suspensions of Dictyostelium discoideum during differentiation and attractant stimulation. The cells maintained an external level of 3-8 microM Ca++ until the beginning of aggregation and then started to take up Ca++. The attractants, folic acid, cyclic AMP, and cyclic GMP, induced a transient uptake of Ca++ by the cells. The response was detectable within 6 s and peaked at 30 s. Half-maximal uptake occurred at 5 nM cyclic AMP or 0.2 microM folic acid, respectively. The apparent rate of uptake amounted to 2 X 10(7) Ca++ per cell per min. Following uptake, Ca++ was released by the cells with a rate of 5 X 10(6) ions per cell per min. Specificity studies indicated that the induced uptake of Ca++ was mediated by cell surface receptors. The amount of accumulated Ca++ remained constant as long as a constant stimulus was provided. No apparent adaptation occurred. The cyclic AMP-induced uptake of Ca++ increased during differentiation and was dependent on the external Ca++ concentration. Saturation was found above 10 microM external Ca++. The time course and magnitude of the attractant-induced uptake of external Ca++ agree with a role of Ca++ during contraction. During development the extracellular Ca++ level oscillated with a period of 6-11 min. The change of the extracellular Ca++ concentration during one cycle would correspond to a 30-fold change of the cellular free Ca++ concentration.

Evidence of cyclic GMP may regulate the association of myosin II heavy chain with the cytoskeleton by inhibiting its phosphorylation

1991 ◽  
Vol 98 (4) ◽  
pp. 483-490
Author(s):  
G. Liu ◽  
P.C. Newell
Keyword(s):  
Cyclic Amp ◽  
Heavy Chain ◽  
Cyclic Gmp ◽  
Parental Strain ◽  
Type Strain ◽  
Wild Type Strain ◽  
Myosin Ii ◽  
Wild Type ◽  
In The Wild

Previous studies have implicated cyclic GMP in the regulation of myosin II heavy chain (MHC) association with the cytoskeleton in Dictyostelium discoideum. Here we provide evidence that cyclic GMP may regulate MHC association with the cytoskeleton through MHC phosphorylation. Comparative data are presented of MHC phosphorylation in the wild-type strain NC4, the parental strain XP55 and streamer mutants NP368 and NP377. Using an anti-MHC monoclonal antibody to immunoprecipitate MHC from [32P]phosphate-labelled developing cells, we found that cyclic AMP stimulation of the wild-type strain NC4 and parental strain XP55 induced MHC phosphorylation in vivo. A peak of phosphorylation was observed at 30–40 s, followed by a gradual decrease to basal level at 160 s. In contrast, in both of the streamer mutants NP368 and NP377 (which have prolonged cyclic GMP accumulation and prolonged MHC association with the cytoskeleton), the phosphorylation of MHC was delayed and did not form a peak until 60–80 s after cyclic AMP stimulation. We also found that cytoskeletal MHC showed only minor phosphorylation, the majority of the phosphorylated MHC being found in the cytosol. We present a model to account for these results in which cyclic GMP regulates MHC association with the cytoskeleton by regulating the phosphorylation/dephosphorylation cycle of MHC in these cells.

Sign in / Sign up

Export Citation Format

Share Document