CSM News
Electronic Edition
Volume 4, number 23
June 24, 1995

Please submit abstracts of your papers as soon as they have been
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==============
 Announcement
==============

Because of Dicty95 there will be no CSM-News next week.  Hope to see
many of you there!

===========
 Abstracts
===========

cAMP DEPENDENT PROTEIN KINASE ACTIVITY IS ESSENTIAL FOR PREAGGREGATIVE
GENE INDUCTION IN DICTYOSTELIUM.

Conchita Schulkes and Pauline Schaap

Cell Biology Section, Institute for Molecular Plant Sciences,
University of Leiden, Wassenaarseweg 64, 2333 AL Leiden, The
Netherlands

SUMMARY
   
   Constitutive inhibition of cAMP dependent protein kinase (PKA) in
Dictyostelium cells blocks cell aggregation and development. We
investigated the cause of the aggregation defect in transformants
overexpressing dominant-negative PKA regulatory subunits (PKA-RM)
under an actin15 promoter. These mutants could not relay pulses of the
chemoattractant cAMP, due to a defect in expression of the aggregative
adenylyl cyclase (ACA) gene. Unstimulated and cAMP pulse-induced
expression of other aggregative genes encoding the cAMP receptor cAR1,
adhesive contact sites A and cAMP-phosphodiesterase were also strongly
reduced in the mutants. Additionally, the expression of the discoidin
I gene, that is expressed early in development in response to cell
density sensing factors, was almost completely absent. These data are
in interesting contrast with observations that cAMP relay and
aggregative gene expression are normal in null mutants for the PKA
catalytic (C) subunit and suggest the presence of multiple C subunit
genes in Dictyostelium and an almost universal requirement for PKA
activity in developmental gene expression.

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[End CSM News, volume 4, number 23]