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Molecular and Cellular Biology, October 1999, p. 7276-7286, Vol. 19, No. 10
Division of Biological Science, Graduate
School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
Received 9 November 1998/Returned for modification 7 January
1999/Accepted 14 July 1999
Mitogen-activated protein kinase (MAPK) is a conserved eukaryotic
signaling factor that mediates various signals, cumulating in the
activation of transcription factors. Extracellular signal-regulated kinase (ERK), a MAPK, is activated through phosphorylation by the
kinase MAPK/ERK kinase (MEK). To elucidate the extent of the involvement of ERK in various aspects of animal development, we searched for a Drosophila mutant which responds to elevated
MEK activity and herein identified a lace mutant. Mutants
with mild lace alleles grow to become adults with multiple
aberrant morphologies in the appendages, compound eye, and bristles.
These aberrations were suppressed by elevated MEK activity. Structural
and transgenic analyses of the lace cDNA have revealed that
the lace gene product is a membrane protein similar to the
yeast protein LCB2, a subunit of serine palmitoyltransferase (SPT),
which catalyzes the first step of sphingolipid biosynthesis. In fact,
SPT activity in the fly expressing epitope-tagged Lace was absorbed by
epitope-specific antibody. The number of dead cells in various imaginal
discs of a lace hypomorph was considerably increased,
thereby ectopically activating c-Jun N-terminal kinase (JNK), another
MAPK. These results account for the adult phenotypes of the
lace mutant and suppression of the phenotypes by elevated
MEK activity: we hypothesize that mutation of lace causes
decreased de novo synthesis of sphingolipid metabolites, some of which
are signaling molecules, and one or more of these changes activates JNK
to elicit apoptosis. The ERK pathway may be antagonistic to the JNK
pathway in the control of cell survival.
0270-7306/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
De Novo Synthesis of Sphingolipids Is Required for
Cell Survival by Down-Regulating c-Jun N-Terminal Kinase in
Drosophila Imaginal Discs
*
Corresponding author. Mailing address: Division of
Biological Science, Graduate School of Science, Nagoya University,
Chikusa-ku, Nagoya 464-8602, Japan. Phone: 81-52-789-5039. Fax:
81-52-789-2511. E-mail: adachi{at}bio.nagoya-u.ac.jp.
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