Eukaryotic microbe system

Alberts et al. information on:
Dictyostelium discoideum - especially 831-833, also 838, 846-847
Saccharomyces cerevisiae - 441-442, 833-834, 521-522, 721-722

classic paper: J. T. Bonner, Hormones in social amoebae and mammals, Scientific American, June, 1969, pp 78-91

Fig. 16-62, p. 832 shows the chemotaxix of a cell
Fig. 16-63, p. 832 shows the involvement of sudden actin development
Fig. 16-60, p. 831 shows the slug
Fig. 16-61 p. 831 shows the fruiting body

The discovery that the receptor was related to the G protein linked receptor (e.g. the beta adrenergic receptor)


P. S. Klein et al. A chemoattractant receptor controls development in Dictyostelium discoideum, Science 241 615-616

and cf.

J. L. Marx, Receptors highlighted at NIH symposium (research news) Science 238 615-616

main points
the 7 transmembrane protein (inferred from hydrophobicity plot) is the cAMP (pheromone) receptor and signals through the G protein to an adenylyl cyclase which makes cAMP for export. The receptor can be phosphorylated. A phosphodiesterase is out there to break down cAMP. The receptor looks like the metabotropic adrenergic receptor. A PDE outside the cell can brak down the cAMP.

Recent research
reserve paper:
J. Van Houten, Chemosensory transduction in eukaryotic microorganisms: trends for neuroscience? Trends in Neurosciences 17 62-71, 1994.

slime mold
detect bacteria ("prey") by folic acid, but cAMP signalling better understood
cAMP secreted in waves, phosphorylation and PDE help avoid self detection
in addition to aggregation, cAMP also used in prestalk and prespore
several receptor genes (cAR1-4) and 6 G protein genes
note that the calcium that comes as a result of PLC comes from intracellular stores and from extracellular sources
note here that PLC is delta type

haploid mating types a and a
peptides a-factor (13 a.a.) and alpha-factor (12 a.a.)
interestingly a-factor is secreted by multidrug-resistance transporter (&CFTR)
receptors are 7-transmembrane, but share no homology (convergent evolution?)
can be replaced by beta adrenergic
G protein, but beta and gamma more important than in the typical cascade
->-> (cascade)kinase arrests in G1 of cell cycle

paper also discusses sea-urchin spermatozoa
egg releases pheromones speract or resact, depending on species
guanylate cyclase is receptor and generates second messenger
as is: 1receptor for atrial natriuretic peptide (relax blood vessels and makes kidney
secrete sodium)
and E. coli enterotoxin receptor

paper also discusses several examples of chemoreception in ciliates
mating pheromones in Euploites
and, in Paramecia, folic acid and cAMP and glutamate

some important terminology introduced in end of paper
ERK = extracellular-signal-regulated kinase
= MAPK = mitogen activated protein kinase
phosphorylated by MEK = MAPK kinase (MAPKK) or ERK kinase (ERKK)

This page was last updated on Dec. 19, 2001

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