Identification of gravity-transducers in skeletal muscle cells: Physiological relevance of tension fluctuations in plasma membrane (Cell Mechanosensing-1) - 07.29.14

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Identification of gravity-transducers in skeletal muscle cells:  Physiological relevance of tension fluctuations in plasma membrane (Cell Mechanosensing-1) is an investigation that identifies gravity sensors in skeletal muscle cells in order to develop countermeasures to muscle atrophy, a key space health issue. Scientists believe that the lack of mechanical stress from gravity causes tension fluctuations in the plasma membrane of skeletal muscle cells, which changes the expression of key proteins and genes, and allows muscles to atrophy. Muscle cells from rats, and kidney cells from African clawed frogs are tagged with fluorescent gene markers, and  attached to an extracellular matrix to study their performance under different tensions, simulating use on earth.
 

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This content was provided by Masahiro Sokabe, and is maintained in a database by the ISS Program Science Office.
Information provided courtesy of the Japan Aerospace and Exploration Agency (JAXA).

Experiment Details

OpNom

Principal Investigator(s)

  • Masahiro Sokabe, Nagoya University Graduate School of Medicine, Japan

  • Co-Investigator(s)/Collaborator(s)
  • Takeshi Nikawa, Ph.D., M.D., University of Tokushima, Tokushima, Japan

  • Developer(s)
    JAXA TKSC Space Environment Utilization Center, Tsukuba, , Japan

    Sponsoring Space Agency
    Japan Aerospace Exploration Agency (JAXA)

    Sponsoring Organization
    Unknown

    Research Benefits
    Information Pending

    ISS Expedition Duration
    March 2014 - September 2014

    Expeditions Assigned
    39/40

    Previous ISS Missions
    Myolab

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    Experiment Description

    Research Overview

    • Skeletal muscle is sensitive to mechanical stress. For example, it easily atrophies under microgravity conditions, while exercise stimulates its growth. Several lines of investigation suggest that skeletal muscle cells possess unique sensors for mechanical stress. However, this sensing mechanism of mechanical stress remains unknown. Based on previous studies, it is hypothesized that tension fluctuation in salcolemma (the plasma membrane of skeletal muscle cells) plays an important role in sensing mechanical stress, such as microgravity. Mechanical stress causes changes in tension fluctuation in the salcolemma, resulting in the activation of channels and/or proteases on membrane surface. They transduce intracellular signaling in skeletal muscle cells to express muscle atrophy-associated ubiquitin ligases (atrogenes), including Cbl-b, MAFbx/atrogin-1, and MuRF-1. We have already reported two candidate transducers, MSCL and MSPL. The former is a mechanosensitive channel with a large pore (MSCL) which induces a Calcium Ion (Ca2+) influx. The latter is Mosaic Serine Protease, large form (MSPL) which mediates the shedding of bioactive membrane molecules. In this study, we will clarify the mechanism on how the tension fluctuation in the salcolemma regulates activities of such transducers during microgravity conditions. We will cultureL6 myotubes/myoblastic cells and A6 amphibian cells on extracellular matrices with different rigidity in the ‘Kibo’ module of the International Space Station. Additionally, the activities of MSCL and MSPL will be measured, as well as the myotube formation of L6 cells. Furthermore, it is hoped that development of inhibitors of these molecules to combat microgravity-induced muscle atrophy will be possible.

    • Mechanical stress changes in tension fluctuation in cell membrane, resulting in activation of channels and/or proteases on membrane surface.

    • The experiment will clarify the mechanism how the tension fluctuation in cell membrane regulate activities of such transducers during microgravity conditions. The experiment will cultureL6 cells with different rigidity in 'Kibo' module of the International Space Station, so that microgravity conditions induce distinct tension fluctuation in cell membrane.

    • I will measure the activities of channels on cell membrane, and muscle fiber formation of L6 cells. Furthermore, PI will develop inhibitors of these molecules, to combat microgravity-induced muscle atrophy.

    Description

    Mechanical stress changes in tension fluctuation in cell membrane, resulting in activation of channels and/or proteases on membrane surface. The experiment will clarify the mechanism how the tension fluctuation in cell membrane regulate activities of such transducers during microgravity conditions. The experiment will culture L6 myotubes/myoblastic cells on extracellular matrix with different rigidity in “Kibo” module of the International Space Station, so that microgravity conditions induce distinct tension fluctuation in cell membrane. Finally, PIs will measure the activities of channels and/or proteases on membrane, and myotube formation of L6 cells. Furthermore, we will develop inhibitors of these molecules, to combat microgravity-induced muscle atrophy.
     

    Cell Mecahonsensing-1 will continue to Cell Mechanosensing-2 which utilizesGreen Flourescence otien (GFP) recombinant cells with fluorescence microscope observation.


    JAXA CBEF,   Measurement Experiment Culture Chambers and Measurement Experiment Cages are used for incubation. Measurement Experiment Solution Exchangers are used for medium/fixative exchange.
     

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    Applications

    Space Applications

    The results of this experiment will give information to develop pharmaceuticals to combat microgravity-induced muscle atrophy.
     

    Earth Applications

    The results of this experiment will give information to develop pharmaceuticals to treat muscle atrophy of bed-bound patients.
     

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    Operations

    Operational Requirements

    The samples (L6 cells) are incubated in JAXA CBEF with micro gravity and artificial 1g environment. L6 cells are cultured in Measurement Experiment Culture Chambers with Measurement Experiment Cages in CBEF. Medium with/without inhibitors are exchanged using Measurement Experiment Solution Exchanger by crew operation. At last the cells are fixed with Paraformaldehyde or RNAlater using Measurement Experiment Solution Exchanger for recovery (at -95° C).

    Operational Protocols

    Launch active L6 cells at ambient then starts incubation in CBEF soon after docking. After 9 days of incubation, exchange medium (with/without inhibitors). After one day from medium exchange, the cells are fixed using RNAlater and kept frozen in MELFI at -95° C.

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    Results/More Information
    Information Pending

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    Related Websites

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    Imagery