A new study finds that humans and corals share a key biomechanical pathway that tells cells when to die.
We humans climb trees, compose operas, and send rockets to the far corners of the universe. Corals, on the other hand, just kind of sway there at the bottom of the sea. It’s hard to imagine a creature with seemingly less in common with humans, but a recent study by San Diego State University biologists has discovered that both species share a 500-million-year-old biomechanical pathway responsible for triggering cellular self-destruction. That might sound scary, but killing off defective cells is essential to keeping an organism healthy.
SDSU graduate student Steven Quistad found that humans and corals use the same protein pathway to trigger apoptosis, or cell death, meaning this pathway evolved some 500 million years ago.
The finding will help biologists to advance their understanding of the early evolution of multicellular life, conservationists to better understand the plight of modern corals, and medical researchers to develop new drugs to fight diseases like cancer.
Steven Quistad, a graduate student working in the lab of SDSU virologist Forest Rohwer, made the discovery earlier this year somewhat by accident. Rohwer leads SDSU's Viral Information Institute, one of the university's Areas of Excellence. The cross-disciplinary institute explores interactions between viruses and the biosphere in order to improve human and environmental health.
Like Rohwer, Quistad has spent most of his research career so far studying viruses. While analyzing the proteins of the coral Acropora digitifera and matching them against human proteins, he found a peculiar similarity: Both had receptor proteins that receive signals from another protein called tumor necrosis factor, or TNF.
When TNF proteins attach themselves to a cell’s TNF receptors, the cell launches into an orderly self-destruct mode. The protein strands inside the cell break down and the cellular components are cordoned off and carried away to be recycled. The process, known as apoptosis, plays a crucial role in cellular health, allowing defective cells to destroy themselves before they can cause damage to the organism.
When Quistad looked more closely at the coral’s genome, he noticed that it had genes that coded for not just one TNF receptor, but 40 of them. TNF comes in many different “flavors,” and each one matches with a particular receptor. The coral Quistad investigated had 14 different flavors of TNF and more TNF receptors than any other known organism on the planet. Humans, by comparison, have 25 TNF receptors.
So what would happen if you took the human version of a TNF protein and exposed it to a coral’s TNF receptors? Quistad and his colleagues did just that and watched for the telltale signs of apoptosis. Under a microscope, they saw evidence that the coral cell was breaking down within 10 minutes of exposure to human TNF. A series of other cellular signals associated with apoptosis confirmed it: Human TNF sets into motion programmed cell death in corals.
Next, Quistad and colleagues wondered if coral TNF proteins would trigger apoptosis in human cells. They coaxed E. coli bacteria to express the same TNF proteins produced by corals and exposed them to cultured human tissue. Sure enough, apoptosis occurred in the human cells. Quistad published these results today in the Proceedings of the National Academy of Sciences.
The findings suggest that the pathway by which TNF triggers apoptosis is old. Extremely old.
“The fact that it goes both ways means that these domains haven’t changed in half a billion years,” Quistad said. “Corals are actually much more similar to humans than we ever realized.”
That’s interesting from an evolutionary biology perspective, Quistad said, because approximately 542 million years ago, organized life took off in a very big way. Known as the Cambrian Explosion, this period saw the emergence of the early ancestors of much of the life that exists today, including humans. No one really knows what set off the Cambrian Explosion, but it’s possible the evolution of orderly, systematic cell death played a leading role.
“TNF-induced apoptosis could turn out to be one of the major sparks of the Cambrian Explosion,” Quistad said.
Unfortunately, after half a billion years of success, corals today aren’t doing so well. The effects of climate change and ocean pollution are taking their toll on the atolls. A fatal stress response known as coral bleaching, whereby corals expel the bacteria that give them their vibrant colors, is decimating corals around the world. Previous studies have linked apoptosis to this process, and indeed, the corals to which Quistad exposed TNF eventually bleached out.
A better understanding of how TNF mediates apoptosis in coral might allow conservationists to identify more resilient species, and then reintroduce these hardier corals to places where coral loss is hurting the local ecosystem, Quistad said.
Preserving and learning from these corals is important for human health, too. Corals are wonderfully complex organisms, Quistad said, and we’re only beginning to learn their secrets.
“Many people look at a coral and think it’s just a slimy rock,” he said. “They think, ‘How can it be so complex at a molecular level when it looks so simple?’”
Quistad said that by studying corals’ various flavors of TNF proteins and TNF receptors, researchers might uncover medical properties useful for killing specific kinds of renegade cells, such as cancer cells.
“We have a lot to learn from corals about our own immune system,” he said.
Beth Chee | Eurek Alert!
Zap! Graphene is bad news for bacteria
23.05.2017 | Rice University
Discovery of an alga's 'dictionary of genes' could lead to advances in biofuels, medicine
23.05.2017 | University of California - Los Angeles
An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.
We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...
Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.
Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...
An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...
In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.
In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...
Dental plaque and the viscous brown slime in drainpipes are two familiar examples of bacterial biofilms. Removing such bacterial depositions from surfaces is...
23.05.2017 | Event News
22.05.2017 | Event News
17.05.2017 | Event News
23.05.2017 | Physics and Astronomy
23.05.2017 | Life Sciences
23.05.2017 | Medical Engineering