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Journal of Cell Science, Vol 99, Issue 1 187-191, Copyright © 1991 by Company of Biologists
JOURNAL ARTICLES |
S Menz, J Bumann, E Jaworski and D Malchow
Fakultat fur Biologie, University of Konstanz, FRG.
Previous work has shown that streamer F (stmF) mutants of Dictyostelium discoideum exhibit prolonged chemotactic elongation in aggregation fields. The mutants carry an altered structural gene for cyclic GMP phosphodiesterase resulting in low activities of this enzyme. Chemotactic stimulation by cyclic AMP causes a rapid transient increase in the cyclic GMP concentration followed by association of myosin heavy chains with the cytoskeleton. Both events persist several times longer in stmF mutants than in the parental strain, indicating that the change in association of myosin with the cytoskeleton is transmitted directly or indirectly by cyclic GMP. We measured the cyclic AMP-induced Ca2+ uptake with a Ca(2+)-sensitive electrode and found that Ca2+ uptake was prolonged in stmF mutants but not in the parental strain. The G alpha 2 mutant strain HC33 (fgdA), devoid of InsP3 release and receptor/guanylate cyclase coupling, lacked Ca2+ uptake. However, the latter response and cyclic GMP formation were normal in the signal-relay mutant strain agip 53 where cyclic AMP-stimulated cyclic AMP synthesis is absent. LiCl, which inhibits InsP3 formation in Dictyostelium, blocked Ca2+ uptake in a dose-dependent manner. The data indicate that the receptor-mediated Ca2+ uptake depends on the InsP3 pathway and is regulated by cyclic GMP. The rate of Ca2+ uptake was correlated in time with the association of myosin with the cytoskeleton, suggesting that Ca2+ uptake is involved in the motility response of the cells.
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C Schlatterer, F Gollnick, E Schmidt, R Meyer, and G Knoll Challenge with high concentrations of cyclic AMP induces transient changes in the cytosolic free calcium concentration in Dictyostelium discoideum J. Cell Sci., January 8, 1994; 107(8): 2107 - 2115. [Abstract] [PDF]
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H Flaadt, E Jaworski, and D Malchow Evidence for two intracellular calcium pools in Dictyostelium: the cAMP-induced calcium influx is directed into a NBD-Cl- and 2,5-di-(tert-butyl)1,4-hydroquinone-sensitive pool J. Cell Sci., January 8, 1993; 105(4): 1131 - 1135. [Abstract] [PDF]
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H Flaadt, E Jaworski, C Schlatterer, and D Malchow Cyclic AMP- and Ins(1,4,5)P3-induced Ca2+ fluxes in permeabilised cells of Dictyostelium discoideum: cGMP regulates Ca2+ entry across the plasma membrane J. Cell Sci., January 5, 1993; 105(1): 255 - 261. [Abstract] [PDF]
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