Abstract
Fusion of phagolysosomes has been previously demonstrated to occur during the incubation of phagolysosome-containing homogenates of Acanthamoeba (Oates and Touster, 1978, J. Cell Biol. 79:217-234). Further studies on this system have shown that methylxanthines (0.2 mM) and/or cAMP (0.5-1 mM) markedly accelerate the average rate, but not the extent, of the in vitro phagolysosome fusion process. Adenosine, 5'- AMP, and ADP (0.5-1 mM) were without effect. ATP (0.5-1 mM) caused variable stimulation, whereas beta, gamma-methylene-ATP (1 mM) caused pronounced inhibition, as did GTP (1 mM) and cGMP (1 mM). Stimulation by 3-isobutyl-1-methylxanthine was blocked by GTP, but not by ATP or cAMP. These results indicate that the rate of phagolysosome fusion in Acanthamoeba homogenates may be regulated by cyclic nucleotides, with enhancement of the fusion rate by cAMP and inhibition of the rate by cGMP. The extent of the reaction increased spontaneously and markedly during the first few hours after preparation of the homogenates. This activation appears to be because of a slow conversion of a significant fraction of the vacuole population from a fusion-incompetent to a fusion-competent, cyclic nucleotide-sensitive state.
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Selected References
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- Chasin M., Harris D. N. Inhibitory and activators of cyclic nucleotide phosphodiesterase. Adv Cyclic Nucleotide Res. 1976;7:225–264. [PubMed] [Google Scholar]
- Goldberg N. D., Haddox M. K., Nicol S. E., Glass D. B., Sanford C. H., Kuehl F. A., Jr, Estensen R. Biologic regulation through opposing influences of cyclic GMP and cyclic AMP: the Yin Yang hypothesis. Adv Cyclic Nucleotide Res. 1975;5:307–330. [PubMed] [Google Scholar]
- Hax W. M., Demel R. A., Spies F., Vossenberg J. B., Linnemans W. A. Increased phospholipase A activity and formation of communicative contacts between Acanthamoeba castellanii cells. Effect of 3',5'-cyclic AMP. Exp Cell Res. 1974 Dec;89(2):311–319. doi: 10.1016/0014-4827(74)90795-2. [DOI] [PubMed] [Google Scholar]
- Jamieson J. D., Palade G. E. Condensing vacuole conversion and zymogen granule discharge in pancreatic exocrine cells: metabolic studies. J Cell Biol. 1971 Mar;48(3):503–522. doi: 10.1083/jcb.48.3.503. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Kuo J. F., Greengard P. Cyclic nucleotide-dependent protein kinases. IV. Widespread occurrence of adenosine 3',5'-monophosphate-dependent protein kinase in various tissues and phyla of the animal kingdom. Proc Natl Acad Sci U S A. 1969 Dec;64(4):1349–1355. doi: 10.1073/pnas.64.4.1349. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Oates P. J., Touster O. In vitro fusion of Acanthamoeba phagolysosomes. I. Demonstration and quantitation of vacuole fusion in Acanthamoeba homogenates. J Cell Biol. 1976 Feb;68(2):319–338. doi: 10.1083/jcb.68.2.319. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Oates P. J., Touster O. In vitro fusion of Acanthamoeba phagolysosomes. II Quantitative characterization of in vitro vacuole fusion by improved electron microscope and new light microscope techniques. J Cell Biol. 1978 Oct;79(1):217–234. doi: 10.1083/jcb.79.1.217. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Perkins J. P. Adenyl cyclase. Adv Cyclic Nucleotide Res. 1973;3:1–64. [PubMed] [Google Scholar]
- Rasmussen H., Jensen P., Lake W., Friedmann N., Goodman D. B. Cyclic nucleotides and cellular calcium metabolism. Adv Cyclic Nucleotide Res. 1975;5:375–394. [PubMed] [Google Scholar]
- Rubin C. S., Rosen O. M. Protein phosphorylation. Annu Rev Biochem. 1975;44:831–887. doi: 10.1146/annurev.bi.44.070175.004151. [DOI] [PubMed] [Google Scholar]
- Ryter A., Bowers B. Localization of acid phosphatase in Acanthamoeba castellanii with light and electron microscopy during growth and after phagocytosis. J Ultrastruct Res. 1976 Dec;57(3):309–321. doi: 10.1016/s0022-5320(76)80119-0. [DOI] [PubMed] [Google Scholar]