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Gravity Sensitivity of T-Cell Activation : The Actin Cyto-Skeleton.
B.B. Hashemi1,2, J.E. McClure1,2, and D.L.
Pierson1. 1Life Science Research Laboratories, NASA
- Johnson Space Center, Houston, TX 77058, and 2National Space
Biomedical Research Institute, Baylor College of Medicine, Houston TX
77030.
Experiments performed during space flight indicate an inhibition of human
peripheral T-cell activation in microgravity culture [Hashemi et. al.
FASEB J. 1999 13, (4) 2071].
This inhibition correlates with a lack of activation-induced
polarization of the Microtubule Organizing Center (MTOC) towards the
activation site.
The results indicate that changes in the gravity environment of
T-cells from 1g can have
dramatic effects on their functional responses.
The actin cytoskeleton plays a crucial role in signal transduction and
activation response of T-cells [Destin et. al. Nature Immunology 2000 1,
(1) 23].
In the current study, we evaluate the polymerization state of actin
in the Jurkat Leukemia T-cell line cultured under hypogravity and
hypergravity conditions.
When Jurkat cells are exposed to hypogravity culture by
clinorotation, they exhibit an impairment in the activation-induced
polymerization of F-actin; a response that occurs readily in T-cells that
are cultured in 1g.
Furthermore, exposure of T cells to hypergravity culture has a
dramatic effect on the actin cytoskeleton.
A 30-minute exposure of Jurkat cells to as little as a 2g
hypergravity culture results in a significant decrease in cellular F-actin.
Exposure to higher centrifugal forces in the range of 100-300g
for as little as 10 minutes results in substantially lower levels of
cellular F-actin.
These results are consistent with our earlier findings of
inhibition of T-cell activation responses during space flight, and they
have significant implications for gravitational biology as they suggest an
important role for the actin cytoskeleton in gravity sensitivity of T-cell
activation.
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