dictyNews
Electronic Edition
Volume 40, number 3
January 24, 2014

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Abstracts
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Evolution of the nucleus

Damien P. Devos, Ralph Gräf and Mark C. Field


Current Opinion in Cell Biology, in press

The nucleus represents a major evolutionary transition. The consequence 
of separating translation from transcription allowed many new functions to 
arise, which likely contributed to the remarkable success of eukaryotic cells. 
Here we will consider what has recently emerged on the evolutionary 
histories of several key aspects of nuclear biology; the nuclear pore 
complex, the lamina, centrosomes and evidence for prokaryotic origins 
of important players.


Submitted by Ralph Gräf [[log in to unmask]]
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An ancestral non-proteolytic role for presenilin proteins in multicellular 
development of the social amoeba Dictyostelium discoideum

Marthe H.R. Ludtmann*, Grant P. Otto*, Christina Schilde, Zhi-Hui Chen, 
Claire Y. Allan, Selina Brace, Philip W. Beesley, Alan R. Kimmel, 
Paul Fisher, Richard Killick, Robin S.B. Williams


Journal of Cell Science, in press

Mutations in two presenilin genes cause familial Alzheimer’s disease. 
Presenilins have both proteolysis-dependent functions as components of 
the gamma-secretase complex and proteolysis independent functions in 
signalling. In this study we investigate a conserved function of human 
presenilins in the development of the simple model Dictyostelium 
discoideum. We show that the block in Dictyostelium development caused 
by ablation of both Dictyostelium presenilins is rescued by expression of 
human presenilin 1, restoring terminal differentiation of multiple cell types. 
This developmental role is independent of proteolytic activity, since 
mutation of both catalytic aspartates does not affect presenilin ability to 
rescue development, and ablation of nicastrin, a gamma-secretase 
component critical for proteolytic activity, does not block development. 
The role of presenilins during Dictyostelium development is therefore 
independent of their proteolytic activity. However, presenilin loss in 
Dictyostelium results in elevated cyclic AMP (cAMP) levels and enhanced 
stimulation-induced calcium release, suggesting that presenilins regulate 
these intracellular signalling pathways. Our data suggest that presenilin 
proteins perform an ancient non-proteolytic role in regulating intracellular 
signalling and development, and that Dictyostelium is a useful model for 
analysing human presenilin function.


Submitted by Robin Williams [[log in to unmask]]
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[End dictyNews, volume 40, number 3]