dictyNews
Electronic Edition
Volume 48, number 16
August 19, 2022
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Abstracts
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Nguyen LTS and Robinson DN*.
The lectin Discoidin I acts in the cytoplasm to help assemble the
contractile machinery.
J. Cell Biol. 2022; in press
Cellular functions, such as division and migration, require cells to
undergo robust shape changes. Through their contractility machinery,
cells also sense, respond, and adapt to their physical surroundings.
In the cytoplasm, the contractility machinery organizes into higher-
order assemblies termed contractility kits (CKs). Using Dictyostelium
discoideum, we previously identified Discoidin I, a classic secreted
lectin, as a CK component through its physical interactions with the
actin crosslinker cortexillin I (CortI) and the scaffolding protein
IQGAP2. Here, we find that DscI ensures robust cytokinesis through
regulating intracellular components of the contractile machinery.
Specifically, DscI is necessary for normal cytokinesis, cortical
tension, membrane-cortex connections, and cortical distribution and
mechanoresponsiveness of cortexillin I. The dscI deletion mutants
also have complex genetic epistatic relationships with CK
components, acting as a genetic suppressor of cortI and iqgap1,
but as an enhancer of iqgap2. This work underscores the fact that
proteins like Discoidin I contribute in diverse ways to the activities
necessary for optimal cell function.
Submitted by Douglas Robinson [[log in to unmask]]
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The polyketide synthase StlA is involved in inducing aggregation in
Polysphondylium violaceum
Daiki T. Yamasaki, Tsuyoshi Araki and Takaaki B. Narita*
*Department of Life Science, Faculty of Advanced Engineering, Chiba
Institute of Technology
Bioscience, Biotechnology, and Biochemistry, accepted
In the social amoeba Dictyostelium discoideum, the polyketide MPBD
(4-methyl-5-pentylbenzene-1,3-diol) regulates the gene expressions
of cAMP signaling to make cells aggregation-competent and also I
nduces spore maturation. The polyketide synthase StlA is responsible
for MPBD biosynthesis in D. discoideum and appears to be conserved
throughout the major groups of the social amoeba (Dictyostelia). In this
study, we analyzed the function of StlA in Polysphondylium violaceum
by identifying the gene sequence and creating the knockout mutants.
We found that Pv-stlA- mutants had defects only in cell aggregation
but not in spore maturation, indicating that the function of StlA in
inducing spore maturation is species-specific. We also found that
MPBD could rescue the aggregation defect in Pv-stlA- mutants whereas
the mutants normally exhibited chemotaxis to their chemoattractant,
glorin. Our data suggest that StlA is involved in inducing aggregation
in P. violaceum by acting on signaling pathways other than chemotaxis
in P. violaceum.
Submitted by Takaaki Narita [[log in to unmask]]
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[End dictyNews, volume 48, number 16]
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