dictyNews
Electronic Edition
Volume 45, number 19
August 9, 2019
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Abstracts
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Elastic modulus of Dictyostelium is affected by mechanotransduction
Yan Wu1 and Kate M. Cooper2
1. University of Wisconsin - Platteville
2. Loras College
Journal of Biological Physics, accepted
https://rdcu.be/bMxuI
The stiffness of adherent mammalian cells is regulated by the elasticity
of substrates due to mechanotransduction via integrin-based focal
adhesions. Dictyostelium discoideum is an ameboid protozoan model
organism that does not carry genes for classical integrin and can adhere
to substrates without forming focal adhesions. It also has a life cycle that
naturally includes both single-cellular and multicellular life forms. In this
article, we report the measurements of the elastic modulus of single cells
on varied substrate stiffnesses and the elastic modulus of the multicellular
“slug” using atomic force microscopy (AFM) as a microindenter/force
transducer. The results show that the elastic modulus of the Dictyostelium
cell is regulated by the stiffness of the substrate and its surrounding cells,
which is similar to the mechanotransduction behavior of mammalian cells.
submitted by: Kate Cooper [[log in to unmask]]
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Actin waves and dynamic patterning of the plasma membrane
Authors: Günther Gerisch1*, Jana Prassler1, Nelson Butterfield1,
Mary Ecke1
1Max Planck Institute of Biochemistry, Am Klopferspitz 18, D-82152
Martinsried Germany
*Corresponding author
Yale Journal of Biology and Medicine, 92, (2019), accepted
Plasma membrane and underlying actin network are connected to a
functional unit that by non-linear interactions is capable of forming
patterns. For instance, in cell motility and chemotaxis, cells polarize to
form a protruding front and a retracting tail. Here we address dynamic
patterns that are formed on a planar substrate surface and are therefore
easily accessible to optical recording. In these patterns two distinct areas
of the membrane and actin cortex are interconverted at the site of circular
actin waves. The inner territory circumscribed by a wave is distinguished
from the external area by a high PIP3 content and high Ras activity. In
contrast, the external area is occupied with the PIP3-degrading phosphatase
PTEN. In the underlying cortex, these areas differ in the proteins associated
with the actin network. Actin waves can be formed at zones of increasing as
well as decreasing Ras activity. Both types of waves are headed by myosin IB.
When waves collide, they usually extinguish each other, and their decay is
accompanied by the accumulation of coronin. No membrane patterns have
been observed after efficient depolymerization of actin, suggesting that
residual actin filaments are necessary for the pattern generating system to
work. Where appropriate, we relate the experimental data obtained with
Dictyostelium to human normal and malignant cell behavior, in particular to
the role of Ras-GAP as an enhancer of macropinocytosis, to mutations in the
tumor suppressor PTEN, to frustrated phagocytosis, and to the role of coronin
in immune cells and neurons.
submitted by: Günther Gerisch [[log in to unmask]]
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[End dictyNews, volume 45, number 19]
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