Meet the microscopic jack-of-all-trades SUMO, which aids in weightlessness in space

If we ever want to be able to live comfortably in a space colony, our bodies must first become more resistant to weightlessness and cosmic radiation. The SUMO peptide may offer a solution.

SUMO peptides are essential in living cells. They bind to proteins and thus guide all kinds of chemical processes in our body in the right direction. It now appears that SUMO (an English abbreviation of Small ubiquitin type modifier) also plays an important role in how the human body handles weightlessness.

fit the astronauts
A recent American study Oklahoma State University shows how the cells of the body “feel” that there is no gravitational force on them and how the cells react to this state of weightlessness. This information could prove invaluable as scientists frantically search for ways to keep astronauts fit and healthy on future space missions, including protecting them from harmful cosmic rays.

The “microgravity” that exists in space triggers a specific type of stress response within the cell. A research team led by molecular biologist Rita Miller studied these protein processes and discovered that the protein modifier SUMO plays a key role in the cell’s adaptation process to a state of weightlessness. The researchers levitated cells in the lab using a NASA-developed device, while using an advanced microscope to observe what changed at the molecular level in the cell.

Microscopic jack-of-all-trades
“We know that under normal gravity, SUMO reacts to stress in different ways. The peptide plays an important role in many processes at the cellular level, such as DNA damage repair, regulation of the cytoskeleton (the network of fibers and tubes that give the cell its rigidity, shape and motility), transcription of genes, management of cell division and replacement of obsolete proteins,” says Professor Miller. “But our study now shows for the first time that SUMO also plays a key role in the cellular response to microgravity.”

Humans have three different SUMO peptides that are busy working in cells. They are small: they consist of only a hundred amino acids and are mainly found in the cell nucleus. Science is learning more and more about how this jack-of-all-trades works, for example the role SUMO plays in the development of cancer. SUMO peptides stabilize enzymes and transport proteins in and out of the cell nucleus by binding to specific proteins. This coupling and uncoupling process is the result of a series of enzymatic reactions. Scientists call these changes SUMOylation or deSUMOylation.

Light yeast
SUMO can chemically bond to a protein in two ways: a non-covalent bond (in which no electrons are shared between the binding partners) and a covalent bond (in which there are one or more common electron pairs). The researchers examined both types of interactions within yeast cells, which are often used to study cellular processes, under the microscope. Half of the cells analyzed are the result of six cell divisions under normal Earth conditions, while the other half of the yeast cells are born after six divisions in simulated microgravity, such as in space.

much more active SUMO
The specific bindings of SUMO peptides and the amount of protein expression of the two groups of yeast cells were compared. In weightlessness, SUMO proved to be much more active than in normal gravity. The researchers counted no less than 37 proteins that couple more than 50% more often with SUMO in microgravity. These included proteins involved in DNA repair. And that’s super important in space because of cosmic ray damage.

“SUMO can have many different functions in the cell. Our study will hopefully lead to a better understanding of the regulation of the series of enzymatic reactions in microgravity involving this particular peptide,” concludes Miller. The follow-up study is already planned and will focus on the potentially harmful influence of the lack of SUMO peptides in the cell in weightlessness. The team wants to know if this leads to a degradation in the performance of certain proteins and to what extent this is harmful to the cell.