Calcium, cyclic GMP and the control of myosin II during chemotactic signal transduction ofDictyostelium

1995 ◽  
Vol 20 (3) ◽  
pp. 289-310 ◽  
Author(s):  
Peter C. Newell
Keyword(s):  
Signal Transduction ◽  
Cyclic Gmp ◽  
Myosin Ii

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.

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 Genetic Analysis Demonstrates a Direct Link Between Rho Signaling and Nonmuscle Myosin Function During Drosophila Morphogenesis

Genetics ◽  
2000 ◽  
Vol 155 (3) ◽  
pp. 1253-1265 ◽  
Author(s):  
Susan R Halsell ◽  
Benjamin I Chu ◽  
Daniel P Kiehart
Keyword(s):  
Signal Transduction ◽  
Myosin Ii ◽  
Signal Transduction Pathway ◽  
P Element ◽  
Nonmuscle Myosin ◽  
Genetic Screens ◽  
Induced Mutations ◽  
Nonmuscle Myosin Ii ◽  
Carboxyl Terminal ◽  
Actomyosin Cytoskeleton

Abstract A dynamic actomyosin cytoskeleton drives many morphogenetic events. Conventional nonmuscle myosin-II (myosin) is a key chemomechanical motor that drives contraction of the actin cytoskeleton. We have explored the regulation of myosin activity by performing genetic screens to identify gene products that collaborate with myosin during Drosophila morphogenesis. Specifically, we screened for second-site noncomplementors of a mutation in the zipper gene that encodes the nonmuscle myosin-II heavy chain. We determined that a single missense mutation in the zipperEbr allele gives rise to its sensitivity to second-site noncomplementation. We then identify the Rho signal transduction pathway as necessary for proper myosin function. First we show that a lethal P-element insertion interacts genetically with zipper. Subsequently we show that this second-site noncomplementing mutation disrupts the RhoGEF2 locus. Next, we show that two EMS-induced mutations, previously shown to interact genetically with zipperEbr, disrupt the RhoA locus. Further, we have identified their molecular lesions and determined that disruption of the carboxyl-terminal CaaX box gives rise to their mutant phenotype. Finally, we show that RhoA mutations themselves can be utilized in genetic screens. Biochemical and cell culture analyses suggest that Rho signal transduction regulates the activity of myosin. Our studies provide direct genetic proof of the biological relevance of regulation of myosin by Rho signal transduction in an intact metazoan.

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.

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