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!
A new potential biomarker for cancer imaging
05.02.2016 | Universiti Putra Malaysia (UPM)
NIH researchers identify striking genomic signature shared by 5 types of cancer
05.02.2016 | NIH/National Human Genome Research Institute
Automobiles increase the mobility of their users. However, their maneuverability is pushed to the limit by cramped inner city conditions. Those who need to...
Advance in biomedical imaging: The University of Würzburg's Biocenter has enhanced fluorescence microscopy to label and visualise up to nine different cell structures simultaneously.
Fluorescence microscopy allows researchers to visualise biomolecules in cells. They label the molecules using fluorescent probes, excite them with light and...
NASA's follow-on to the successful ICESat mission will employ a never-before-flown technique for determining the topography of ice sheets and the thickness of sea ice, but that won't be the only first for this mission.
Slated for launch in 2018, NASA's Ice, Cloud and land Elevation Satellite-2 (ICESat-2) also will carry a 3-D printed part made of polyetherketoneketone (PEKK),...
In the last decades, sea level has been rising continuously – about 3.3 mm per year. For reef islands such as the Maldives or the Marshall Islands a sinister picture is being painted evoking the demise of the island states and their cultures. Are the effects of sea-level rise already noticeable on reef islands? Scientists from the ZMT have now answered this question for the Takuu Atoll, a group of Pacific islands, located northeast of Papua New Guinea.
In the last decades, sea level has been rising continuously – about 3.3 mm per year. For reef islands such as the Maldives or the Marshall Islands a sinister...
The ‘Internet of Things’ is growing rapidly. Mobile phones, washing machines and the milk bottle in the fridge: the idea is that minicomputers connected to these will be able to process information, receive and send data. This requires electrical power. Transistors that are capable of switching information with a single electron use far less power than field effect transistors that are commonly used in computers. However, these innovative electronic switches do not yet work at room temperature. Scientists working on the new EU research project ‘Ions4Set’ intend to change this. The program will be launched on February 1. It is coordinated by the Helmholtz-Zentrum Dresden-Rossendorf (HZDR).
“Billions of tiny computers will in future communicate with each other via the Internet or locally. Yet power consumption currently remains a great obstacle”,...
02.02.2016 | Event News
26.01.2016 | Event News
26.01.2016 | Event News
05.02.2016 | Life Sciences
05.02.2016 | Materials Sciences
05.02.2016 | Physics and Astronomy