Thyrotropin receptor and membrane interactions in FRTL-5 thyroid cell strain in microgravity

Area of Science:

• Space biology
• Cell biology
• Endocrinology

Background:

• Thyrotropin (TSH) receptors are crucial for thyroid cell function, regulating membrane fluidity and stimulating proliferation.
• TSH receptors are located in specific cell membrane microdomains (caveolae and lipid rafts) rich in sphingomyelin and cholesterol.
• Understanding TSH receptor behavior in microgravity is essential for astronaut health during space missions.

Purpose of the Study:

• To investigate the impact of microgravity on thyrotropin (TSH) receptors in FRTL-5 thyroid cells.
• To determine if TSH receptor alterations in microgravity explain the lack of thyroid cell proliferation in space.
• To analyze changes in cell morphology, membrane composition, and protein expression under simulated microgravity.

Main Methods:

• Exposure of FRTL-5 thyroid cell line to microgravity during a parabolic flight (Texus-44 mission).
• Administration of TSH with or without controls during weightlessness (6 minutes, 19 seconds).
• Analysis of cell morphology, TSH receptor shedding, and protein expression (sphingomyelin-synthase, Bax) via onboard and ground controls.

Main Results:

• Cells in microgravity failed to respond to TSH treatment.
• Observed irregular cell shape, condensed chromatin, and cell membrane modification with TSH receptor shedding.
• Detected increased sphingomyelin-synthase and Bax proteins in microgravity-exposed cells.

Conclusions:

• Microgravity induces significant alterations in thyroid cell membrane structure and TSH receptor localization.
• These changes disrupt TSH signaling pathways, leading to inhibited cell proliferation.
• Potential implications for thyroid function and health of astronauts during prolonged space missions.