Dictyostelium discoideum activation

These studies demonstrate the general mechanism of synchronization of biochemical systems, which I expect to be operative in even more complex systems, such as the mitochondrial respiration or the periodic activity of the slime mold Dictyostelium discoideum. As shown in a number of laboratories under suitable conditions mitochondrial respiration can break into self-sustained oscillations of ATP and ADP, NADH, cytochromes, and oxygen uptake as well as various ion transport and proton transport functions. It is important to note that mitochondrial respiration and oxidative phosphorylation under conditions of oscillations is open for the source, namely, oxygen, as well as with respect to a number of sink reactions producing water, carbon dioxide, and heat. 

Bogdanovic A, Bennett N, Kieffer S, Louwagie M, Morio T, et al. 2002. Syntaxin 7, syntaxin 8, Vtil and VAMP7 (vesicle-associated membrane protein 7) form an active SNARE complex for early macropinocytic compartment fusion in Dictyostelium discoideum. Biochem J 368 29-39. 

The activity was purified from Dictyostelium discoideum by differential centrifugation and gel filtration. 

Figure 9.111 Adenylate kinase activity measured by the HPLC assay method. The assay mixture contained 200 fiM ATP, 20 fiM pH]AMP (approximately 120,000 cpm), 50 mM Tris-HCl (pH 7.4), and 32 fig of protein of the enzyme from Dictyostelium discoideum. Samples (20 juL) were injected and the radioactivity monitored continuously with a Berthold LB 503 detector using PICO-Fluor 30 scintillant. Absorbance was measured at 254 nm. Three representative time points were shown (A) 1 minute (B) 30 minutes, and (C) 60 minutes after initiation of the reaction. (From Rosso-mando, 1987.)... 

Van Dijken, P., Bergsma, J.C., Hiemstra, H.S., De Vries, B., Van Der Kaay, J., and Van Haastert, P.J., 1996, Dictyostelium discoideum contains three inositol monophosphatase activities with different substrate specificities and sensitivities to lithium. Biochem. J. 314 491 195. 

The chemotactic response to cAMP of the slime mould Dictyostelium discoideum is presented as an example. When these cells are starving, they sense cAMP signals, and in response to the hunger signal, cAMP, the cells differentiate (reviewed in ref. 67). In Dictyostelium discoideum the response to cAMP is mediated by G-protein-coupled hepta-helical receptors and is transmitted by the Py subunits of a heterotrimeric G protein. In response to the chemoattractant, cAMP, a homologue of PKB (protein kinase B) is rapidly activated by phosphorylation througji a Ptdins kinase specific for the 3-OH position (see also Chapter 4). 

In the slime mould, Dictyostelium discoideum, a STAT-like DNA-binding protein, DIF (the differentiation-inducing factor), is expressed. DIF is about 700 amino-acid residues long, and has substantial homology with mammalian STATs. DIF is, like STAT, activated by phosphorylation of tyrosines. It is essential for differentiation of the stalk cells of D. discoideum A The long evolutionary path that the STATs have travelled from Dictyostelium to mammals underlines their conserved and essential role as signal transmitters and transcriptional activators in early development. 

The most important compounds from this class are undoubtedly 3,6-anhydrofuranoses. Fura-nodictine A and B (produced by cellular slime mold Dictyostelium discoideum) showing neuronal differentiation activity [54] are good examples. These interesting derivatives may be conveniently obtained from the open-chain sugars. For example, synthesis of furanodictine A was realized from compound 85 obtained from D-arabinose in a few well-defined steps as shown inO Fig. 19 [55]. 

Fig. 5. Comparison of conserved and novel sequences of cysteine proteinases in Dictyostelium discoideum. Sequences of four Dictyostelium cysteine proteases and others from mammals and plants deduced from their cDNAs are shown. CPI and CP2 are found only during development. CP4 and CP5 are produced only during vegetative growth and disappear with the onset of development. All of them show the highly conserved (boxed areas) and non-conserved regions (dashed lines) typical of all eukaryotic cysteine proteases. The arrowheads show the conserved active site Cys and His residues. Potential A-glycosylation sites are double underlined.

Distribution and properties of GDH s in over 40 species of fungi have been reviewed by LeJohn (23) who has concluded that, whereas higher fungi of the classes Deuteromycetes, Ascomycetes, and Basidiomycetes possess two distinct enzymes, lower fungi, members of the Phycomycetes and Myxomycetes (slime molds), have only one enzyme active with NAD. However, vegetative cell homogenates of Dictyostelium discoideum possess both an enzyme that is active with NAD and NADP, and one active only with NAD 2Ji). 

GDH s of fungal cells are in the soluble phase of the cytosol. In 1963, it was noted that an NAD-GDH of Puccinia helianthi was separated from mitochondria and microsomes by fractional centrifugation (S9). Both NAD- and NADP-GDH s of S. carlsbergensis and S. cerevisiae are cytoplasmic 90,91). Two possible explanations were offered 90). Location outside mitochondria may represent an adaptation to strong repression exerted by glucose on all mitochondrial enzymes in yeast. Alternatively, evolution of a mitochondrial GDH is a late acquisition and coincides with expression of an enzyme that is not specific in its requirements for NAD or NADP. Existence in Dictyostelium discoideum of both a mitochondrial enzyme, which is active with both NAD and NADP, and an extramitochondrial enzyme, which is active only with NAD, tends to support the latter view 4) ... 

Two compounds common in plant metabolism are believed to be precursors of isoprenoid cytokinins in plants adenosine-5 -monophosphate (AMP) and A -isopentenylpyrophos-phate (iPP). As a final product of the mevalonate pathway, the latter substance serves also as a precursor for a wide spectrum of metabolites including some other plant hormones, as abscisic acid, gibberellins and brassinosteroids. The hypothetical scheme of reactions resulting in the formation of iPA, Z and DHZ is given in Fig. 2. The enzyme of entry into isoprenoid cytokinin formation is A -isopentenylpyrophosphate 5 -AMP-A -iso-pentenyltransferase (EC 2.5.1.8, trivially named cytokinin synthetase ). This enzyme activity was first detected in a cell-free preparation from the slime mould Dictyostelium discoideum [7,8]. Later the enzyme from higher plants (cytokinin-independent tobacco callus [9,10] and immature Zea mays kernels [11]) was described and the data were recently summarised in [12], The enzyme is very specific as far as the substrate is concerned [13,14] only the nucleotide AMP can be converted and only iPP (with a double bond in A position) may function as a side chain donor. 

In the slime mould Dictyostelium discoideum, a portion of the cellular NDPK has been shown to be plasma membrane-associated. Furthermore Dictyostelium p>ossesses surface cAMP-receptors, which couple to a G-protein, but NDPK activity appears to be activated by the receptor followed by G-protein activation [22]. This activation could be eliminated by the addition of antibodies against NDPK and it was proposed that NDPK was supplying GTP for G-protein activation. 

Brenner, M. S. Thoms. 1984. Caffeine blocks activation of cAMP synthesis in Dictyostelium discoideum. Dev. Biol. 101 136-46. 

Coukell, M.B. F.K. Chan. 1980. The precocious appearance and activation of an adenylate cyclase in a rapid developing mutant of Dictyostelium discoideum. FEBS Lett. 110 39-42. 

Klein, C. 1976. Adenylate cyclase activity in Dictyostelium discoideum amoebae and its changes diuing differentiation. FEBS Lett. 68 125-8. 

Roos, W. G. Gerisch. 1976. Receptor-mediated adenylate cyclase activation in Dictyostelium discoideum. FEBS Lett. 68 170-2. 

Theibert, A. P.N. Devreotes. 1983. Cyclic 3, 5 -AMP relay in Dictyostelium discoideum Adaptation is independent of activation of adenylate cyclase. 

Roth and Sussman demonstrated the presence of a,a-trehalose synthetase activity in extracts of the micro-organism Dictyostelium discoideum. Their data indicated that the level of a,a-trehalose synthetase activity changes considerably during the morphogenetic sequence. The presence of a,a-trehalose in this micro-organism has also been reported. 

Newell and coworkers found that, during particular stages of fruit construction in Dictyostelium discoideum, four functionally related enzymes accumulated, reached characteristic levels of specific activity, and then disappeared partly or completely. These enzymes were UDP-d-glucose pyrophosphorylase, trehalose 6-phosphate synthetase, UDP-d-galactose 4-epimerase, and UDP-D-galactose polysaccharide n-galactosyl transferase. 

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