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First published online 15 August 2007
doi: 10.1242/dev.000893
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Department of Biochemistry and Molecular Biology and the Oklahoma Center for Medical Glycobiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104 USA
* Author for correspondence (e-mail: Cwest2{at}ouhsc.edu)
Accepted 5 July 2007
Development in multicellular organisms is subject to both environmental and
internal signals. In Dictyostelium, starvation induces amoebae to
form migratory slugs that translocate from subterranean areas to exposed
sites, where they culminate to form sessile fruiting bodies. Culmination,
thought to be regulated by anterior tip cells, is selectively suppressed by
mild hypoxia by a mechanism that can be partially overridden by another
environmental signal, overhead light, or genetic activation of protein kinase
A. Dictyostelium expresses, in all cells, an O2-dependent
prolyl 4-hydroxylase (P4H1) required for O-glycosylation of Skp1, a subunit of
E3SCF-Ub-ligases. P4H1-null cells differentiate the basic pre-stalk
and pre-spore cell types but exhibit a selectively increased O2
requirement for culmination, from
12% to near or above ambient (21%)
levels. Overexpression of P4H1 reduces the O2 requirement to
<5%. The requirement for P4H1 can be met by forced expression of the active
enzyme in either pre-stalk (anterior) or pre-spore (posterior) cells, or
replaced by protein kinase A activation or addition of small numbers of
wild-type cells. P4H1-expressing cells accumulate at the anterior end,
suggesting that P4H1 enables transcellular signaling by the tip. The evidence
provides novel genetic support for the animal-derived O2-sensor
model of prolyl 4-hydroxylase function, in an organism that lacks the
canonical HIF
transcriptional factor subunit substrate target that is a
feature of animal hypoxic signaling.
Key words: Prolyl hydroxylase, Hypoxia, Oxygen, Dictyostelium, Cytoplasmic glycosylation, Skp1
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