What happens if an astronaut needs to take a Tylenol? Would they need a smaller or larger dose? While not your typical research question, Li et al. examined one aspect of this scenario in a recent study that look at the effect of microgravity on P-Glycoprotein (P-gp). P-gp is a drug efflux protein located in the membrane of certain endothelial cells, including those that make up the lining of the blood-brain barrier. In this location P-gp serves to control the movement of some toxins and pharmacological compounds from the tissue into the blood, thereby affecting the concentration of certain drugs in the central nervous systems. To help understand how the protein works under space-like conditions the authors use a strategy known as co-immunoprecipitation (co-IP) to “capture” proteins interacting with P-gp and then examined them using label-free comparative proteomics.

How was PEAKS used?

Analysis of LC-MS/MS data from the the co-IP samples was completed with PEAKS Studio software. From the list of peptides and inferred protein identifications obtain in PEAKS, the authors were able to set-aside any proteins that were identified in the experimental (assay) control, and/or in tissues from control animals (i.e. terrestrial gravity), to focus on those proteins that only interacted with P-gp under simulated microgravity conditions. Downstream bioinformatic tools, including STRING, PANTHER, and DAVID were used for functional annotation of the PEAKS protein list.

Li, Yujuan, et al. “Investigation on P-Glycoprotein Function and Its Interacting Proteins under Simulated Microgravity.” Space: Science & Technology, American Association for the Advancement of Science (AAAS), June 2021, pp. 1–13. Crossref, doi:10.34133/2021/9835728.

Abstract

P-glycoprotein (P-gp) could maintain stability of the nerve system by effluxing toxins out of the blood-brain barrier. Whether it plays a very important role in drug brain distribution during space travel is not yet known. The present study was aimed at investigating P-gp function, expression, and its interacting proteins in a rat brain under simulated microgravity (SMG) by comparative proteomics approach. Rats were tail-suspended to induce short- (7-day) and long-term (21-day) microgravity. P-gp function was assessed by measuring the P-gp ATPase activity and the brain-to-plasma concentration ratio of rhodamine 123. P-gp expression was evaluated by Western blot. 21d-SMG significantly enhanced P-gp efflux activity and expression in rats. Label-free proteomics strategy identified 26 common differentially expressed proteins (DEPs) interacting with P-gp in 7d- and 21d-SMG groups. Most of the DEPs mainly regulated ATP hydrolysis coupled transmembrane transport and so on. Interaction analysis showed that P-gp might potentially interact with heat shock proteins, sodium/potassium ATP enzyme, ATP synthase, microtubule-associated proteins, and vesicle fusion ATPase. The present study firstly reported P-gp function, expression, and its potentially interacting proteins exposed to simulated microgravity. These findings might be helpful not only for further study on nerve system stability but also for the safe and effective use of P-gp substrate drugs during space travel.