WASHINGTON — In 2021, wildfires pillaged the world’s carbon-rich snow forests.
That year, burning boreal forests released 1.76 billion metric tons of carbon dioxide, researchers reported March 2 in a news conference at the annual meeting of the American Association for the Advancement of Science.
That’s a new record for the region, which stores about one-third of the world’s land-based carbon. “It’s also roughly double the emissions in that year from aviation,” said earth system scientist Steven Davis of the University of California, Irvine. The trend, if it continues, threatens to make fighting climate change even more difficult. Boreal forests are part of the taiga, a vast region that necklaces the Earth just south of the Arctic Circle. Blazes in tropical forests like the Amazon tend to garner more attention for their potential to contribute large amounts of climate-warming gases to the atmosphere (SN: 9/28/17). But scientists estimate that on a per area basis, boreal forests store about twice as much carbon in their trees and soils as tropical forests.
Climate change is causing the taiga to warm about twice as fast as the global average. And wildfires are growing more widespread in the region, releasing more of the trapped carbon, which in turn can worsen climate change (SN: 5/19/21).
Davis and his colleagues analyzed satellite data on carbon emissions from boreal regions from 2000 to 2021. In 2021, emissions from boreal wildfires made up a whopping 23 percent of all the CO2 emitted by wildfires around the world, the researchers report in the March 3 Science. In contrast, CO2 emissions during an average year from 2000 to 2021 were about 10 percent.
The record-breaking emissions coincided with widespread heat waves and droughts in Siberia and northern Canada, probably fueled by human-caused climate change.
There’s no data yet to show if 2022 saw a similar surge in emissions. But, Davis said, “there’s not actually that much evidence that this record will stand for long.”
Even as some parts of West Antarctica rapidly melt, raising sea level, large swaths of the ice remain stable for the time being. Scientists have now explored one of those stable spots — an isolated nook where the ocean meets the ice. There, the team found the underside of the ice sculpted into strange grooves, ripples and globes. This environment is “really at the edge” between melting and freezing, says planetary scientist Justin Lawrence. The delicate balance between these two processes is shaping the ice into those strange textures — similar to the way that minerals dissolve and recrystallize to form the beautiful shapes inside limestone caverns. The result, at Kamb Ice Stream, is that massive cracks in the underside of the ice appear to be freezing back together as the beach ball–sized globes fill in the crevasses from above, Lawrence and colleagues report March 2 in Nature Geoscience. This refreezing differs from what’s happening at Antarctica’s Thwaites Glacier. There, scientists recently reported that these cracks, known as basal crevasses, are instead sites of rapid melting (SN: 2/15/23). Understanding what is happening at Kamb will help scientists predict how large parts of the Antarctic coastline that are not currently vulnerable might respond as the world continues to warm due to human-caused climate change. Here’s what’s different about Kamb. Supercold water underlies the ice at Kamb, slowing melting In December 2019, two teams of researchers from New Zealand and the United States visited the Kamb Ice Stream — a type of glacier that consists of a channel of faster-moving ice surrounded by slower ice. Kamb, like much of the rest of the West Antarctic Ice Sheet, rests on a bed that is hundreds of meters below sea level. The New Zealand team used hot water to melt a narrow hole through the ice, just downstream of the “grounding zone,” where the glacier lifts off its muddy bed and floats on the ocean. The U.S. team then lowered a remote-operated vehicle called Icefin down through 580 meters of ice and into the seawater below. The researchers piloted Icefin as far as a kilometer from the borehole, navigating by video transmitted up through a cable. At the time of the expedition, the team operating Icefin was affiliated with Georgia Tech in Atlanta, but has since moved to Cornell University, except for Lawrence. He now works for Honeybee Robotics, a private company in Altadena, Calif. Icefin found that much of the seawater beneath Kamb is about 0.3 degrees Celsius above freezing. But directly below the ice sits a colder layer, a mixture of seawater and glacial meltwater just 0.02 to 0.08 degrees C above freezing. Based on these measurements, Lawrence and his colleagues estimate that the exposed underside of Kamb is melting about 26 centimeters per year. In contrast, recent measurements at the increasingly unstable Thwaites Glacier, about 1,400 kilometers to the northeast, found the seawater at the glacier’s grounding zone 1 to 2 degrees C warmer than at Kamb — and the ice melting 5 to 40 meters per year. The new finding at Kamb makes sense, says New Zealand team member Christina Hulbe, of the University of Otago, because the seabed at Kamb is relatively shallow. So it is not exposed to the deep, warm ocean currents that are hitting Thwaites. Much of Antarctica is fringed by cold ocean environments similar to Kamb, she says. “So just understanding that system is important.” Greenish globs of refrozen ice fill cracks at Kamb As Icefin glided along, its sonars detected massive basal crevasses up to 55 meters across in the ice above. These cracks probably formed as the floating part of the glacier, the ice shelf, flexes up and down with ocean tides. Lawrence and his colleagues guided the ROV into one of these cracks, and found its white, icy sidewalls carved into narrow vertical grooves. Icefin ascended 40 meters up, until the grooves suddenly vanished — replaced by a jumble of ice globes, which seemed to fill the upper half of the crevasse. The globes were greenish — a hue often seen in winter ice that forms on the surface of the ocean. This color makes Lawrence and his colleagues think that the globes form from the ultracold mixture of seawater and meltwater that circulates up into a crack and refreezes, gradually filling in the crack, from the top down, over many decades. They think that this is happening in all of the crevasses they observed. “These crevasses are effectively healing themselves,” he says. This refreezing process might also explain the strange vertical grooves in the walls of the crevasse, Lawrence speculates. As the water freezes, salt is pushed out of the newly forming ice crystals, creating tiny pockets of highly concentrated brine. That dense brine streams down the walls, melting grooves into the ice — similar to the way that salt causes ice to melt when it’s sprinkled onto a sidewalk in the wintertime. To observe the crevasses refreezing under Kamb “is pretty exceptional,” says Ginny Catania, a glaciologist at the University of Texas at Austin who was not part of the project. Those cracks “can propagate all the way to the surface and cause calving” of icebergs, she says, which can shrink the ice shelf if it happens too quickly, destabilizing the glacier and raising sea level. But if the crevasses can actually heal, this could make these ice shelves more resistant to calving — and more stable — than scientists realized, at least as long as the ice continues to be bathed in cold water on the underside. A string of instruments installed in the hole continued to measure the temperature and salinity of the water beneath the ice — transmitting that data up a cable to the ice’s surface, and back home via satellite until the batteries ran out two years later. Those data show that conditions down below remained cool and comfortable for Kamb.
Full-grown snapping shrimp were already known to have some of the fastest claws under the waves. But it turns out they’re nothing compared with their kids.
Juvenile snapping shrimp produce the highest known underwater accelerations of any reusable body part, researchers report February 28 in the Journal of Experimental Biology. While the claws’ top speed isn’t terribly impressive, they go from zero to full throttle in record time.
To deter predators or competitors, snapping shrimp create shock waves with their powerful claws. The shrimp store energy in the flexing exoskeleton of their claw as it opens, latching it in place much like a bow-and-arrow mechanism, says Jacob Harrison, a biologist at Georgia Tech in Atlanta. Firing the claw and releasing this elastic energy produces a speeding jet of water. Bubbles form behind it and promptly implode, liberating a huge amount of energy, momentarily flashing as hot as the sun and creating a deafening crack (SN: 10/3/01).
But it was unclear how early in their lives the shrimp could use this weaponry. “We knew that the snapping shrimp did this really impressive behavior,” Harrison says. “But we really didn’t know anything about how this mechanism developed.”
While a grad student at Duke University, Harrison and his adviser, biomechanist Sheila Patek, reared bigclaw snapping shrimp (Alpheus heterochaelis) from eggs in the laboratory. At 1 month old, the tiny shrimp — less than a centimeter long — began firing their claws when disturbed. The researchers took high-speed video footage of these snaps and calculated their speed.
The wee shrimp could create the collapsing bubbles just like adults. Despite being a tenth the adults’ size or smaller, the juveniles’ claws accelerated 20 times as fast when firing. This acceleration — about 600 kilometers per second per second — is on “the same order of magnitude as a 9-millimeter bullet leaving a gun,” Harrison says. Dracula ants (Mystrium camillae) and some termites produce more explosive bites but aren’t pushing against water. The stinging cells of jellyfish launch their venomous harpoons about 100 times as fast, but their firing mechanism is inherently single use. Snapping shrimp, on the other hand, can fire their claws again and again. The juveniles’ firing and bubble creation weren’t very reliable at the smallest sizes, but the shrimp routinely tried snapping anyway. The team wonders if the young shrimp could be practicing and training the necessary musculature.
If so, that training might ultimately be crucial to the claw’s function, says Kate Feller, a visual ecologist at Union College in Schenectady, N.Y., who studies similarly ultrafast mantis shrimp and was not involved in the new study. “If you were to somehow manipulate the claws so that they couldn’t properly close and they couldn’t snap,” she wonders, “would that affect their ability to develop these mechanisms?”
Understanding the storage of elastic energy in biological materials and how it flows through them is “tricky,” Harrison says. Figuring out how such tiny claws store so much energy without fracturing may help researchers illuminate this superpower.
A surprise ingredient may explain how lemon juice puts the squeeze on kidney stones.
Lemons contain nanoparticles that, when fed to rats, block stone formation, scientists report in the Feb. 22 Nano Letters. If the tiny sacs do the same for humans, the nanoparticles might one day offer a way to prevent kidney stones in people, says pharmaceutical scientist Hongzhi Qiao of Nanjing University of Chinese Medicine.
Lemon juice is a well-known home remedy for kidney stones, which form when minerals crystalize and clump up inside the kidney (SN: 9/21/18). These rocky lumps can knock around in the urinary tract, slicing and dicing tissues as they eventually pass out of the body (SN: 10/31/16). “It’s so, so, so painful,” says Jingyin Yan, a nephrologist at Baylor College of Medicine in Houston who was not part of the new study. Patients may feel sharp pain in their back, side or lower abdomen when they pass a stone, she says. “People describe it as worse than delivering a baby.” Though some medications can help treat kidney stones, many people end up needing surgery to remove them, says Thomas Chi, a urologist at the University of California, San Francisco, also not part of the study. People often imagine kidney stones as tiny pebbles, but sometimes they bulk up like boulders, he adds. “I’ve taken out stones the size of your fist.”
That’s why prevention is key. Scientists already knew that citric acid, which gives lemons their sour power, may do the trick by binding to the minerals that make up stones. But drinking mouth-puckering lemon juice is not so comfortable for patients, Qiao says.
A 2022 clinical trial found that kidney stone patients had trouble downing 120 milliliters — about a half cup — of lemon juice per day. Swilling loads of lemonade can cause dental problems, too. Chi has had patients drink so much that the acidic liquid ate away at their teeth.
So Qiao and colleagues looked for other, more palatable lemon-derived ingredients that might help prevent kidney stones. Inside edible and medicinal plants like ginseng, grapefruit and dandelion, his team has found extracellular vesicle-like nanoparticles, tiny sacs stuffed with molecules including fat, protein and DNA. These nanoparticles exist in lemon juice, too — and the team fed them to rats that had also ingested a substance that promotes kidney stone growth. The zesty particles slowed stone formation, Qiao and colleagues found. The finding suggests these particles curb development of calcium oxalate crystals, the most common culprit of kidney stones. The particles can also soften the stones and make them less sticky, the team showed.
The new work challenges the conventional wisdom on how lemon juice works to combat kidney stones, Chi says. Using lemon nanoparticles to treat people is still a long way off, but the team’s results hold promise, he says. “The faster you can bring a finding like this towards a human clinical trial, the better.”
It took just a 9-volt battery and a little brain zapping to turn science writer Sally Adee into a stone-cold sharpshooter.
She had flown out to California to test an experimental DARPA technology that used electric jolts to speed soldiers’ sniper training. When the juice was flowing, Adee could tell. In a desert simulation that pit her against virtual bad guys, she hit every one.
“Getting my neurons slapped around by an electric field instantly sharpened my ability to focus,” Adee writes in her new book, We Are Electric. That brain-stimulating experience ignited her 10-year quest to understand how electricity and biology intertwine. And she’s not just talking neurons. Bioelectricity, Adee makes the case, is a shockingly underexplored area of science that spans all parts of the body. Its story is one of missed opportunity, scientific threads exposed and abandoned, tantalizing clues and claims, “electroquacks” and unproven medical devices — and frogs. Oh so many frogs.
Adee takes us back to the 18th century lab of Luigi Galvani, an Italian scientist hunting for what gives animals the spark of life. His gruesome experiments on twitching frog legs offered proof that animal bodies generate their own electricity, an idea that was hotly debated at the time. (So many scientists repeated Galvani’s experiments, in fact, that Europe began to run out of frogs.)
But around the same time, Galvani critic Alessandro Volta, another Italian scientist, invented the electric battery. It was the kind of razzle-dazzle, history-shaking device that stole the spotlight from animal electricity, and the fledgling field fizzled. “The idea had been set,” Adee writes. “Electricity was not for biology. It was for machines, and telegraphs, and chemical reactions.” It took decades for scientists to pick up Galvani’s experimental threads and get the study of bioelectricity back on track. Since then, we’ve learned just how much electricity orchestrates our lives, and how much more remains to be discovered. Electricity zips through our neurons, makes our hearts tick and flows in every cell of the body. We’re made up of 40 trillion tiny rechargeable batteries, Adee writes.
She describes how cells use ion channels to usher charged molecules in and out. One thing readers might not expect from a book that illustrates the intricacies of ion channels: It’s surprisingly funny. Chloride ions, for example, are “perpetually low-key ashamed” because they carry a measly -1 charge. Bogus medical contraptions (here’s looking at you, electric penis belts) were “electro-foolery.” In her acknowledgements, Adee jokes about the “life-saving powers of Voltron” and thanks people for enduring her caffeine jitters. That energy thrums through the book, charging her storytelling like a staticky balloon.
Adee is especially electrifying in a chapter about spinal nerve regeneration and why initial experiments juddered to a halt. Decades ago, scientists tried coaxing severed nerves to link up again by applying an electric field. The controversial technique sparked scientific drama, but the idea of using electricity to heal may have been ahead of its time. Fast-forward to 2020, and DARPA has awarded $16 million to researchers with a similar concept: a bioelectric bandage that speeds wound healing.
Along with zingy Band-Aids of the future, Adee describes other sci-fi–sounding devices in the works. One day, for example, surgeons may sprinkle your brain with neurograins, neural lace or neural dust, tiny electronic implants that could help scientists monitor brain activity or even help people control robotic arms or other devices (SN: 9/3/16, p. 10).
Such implants bring many challenges — like how to marry electronics to living tissue — but Adee’s book leaves readers with a sense of excitement. Not only could bioelectricity inspire new and improved medical devices, it could also reveal a current of unexpected truths about the body.
As Adee writes: “We are electrical machines whose full dimensions we have not even yet dreamed of.”
The April 25 Nepal earthquake killed more than 8,000 people and caused several billion dollars in damage, but new research suggests the toll could have been a lot worse.
GPS readings taken during the quake indicate that most of the tremors vibrated through the ground as long shakes rather than quick pulses. That largely spared the low-lying buildings that make up much of Nepal’s capital, Kathmandu, geophysicists report online August 6 in Science. Those same low-frequency rumbles, though, toppled Kathmandu’s handful of larger buildings, such as the historic 62-meter tall Dharahara Tower.
Understanding why the fault produced a quake at such low frequencies could help seismologists better identify future seismic hazards, says Jean-Philippe Avouac of the University of Cambridge. “This could be some good news not only for this major fault, but also potentially for similar faults around the world.”
Nepal sits over a tectonic boundary where the Indian Plate slips under the Eurasian Plate. At places, the two plates snag together, building stress that abruptly releases as an earthquake (SN: 5/16/15, p. 12). Earthquakes stronger than April’s magnitude 7.8 shakedown have hit Nepal before, including a magnitude 8.0 quake in 1934. Despite the recent quake’s feebler intensity, its trembles somehow destroyed large buildings that had previously endured mightier earthquakes.
Avouac and colleagues monitored April’s quake using a network of 35 solar-powered GPS stations, the first time such an accurate system was in place during a major quake on this type of fault. The stations measured ground movements five times each second. The earthquake shook most intensely at 0.25 hertz, or one full wave every four seconds, with only moderate shaking above 1 hertz, or one or more complete waves each second.
A building is most vulnerable when shook near its resonance frequency, a range where even small outside forces can result in big vibrations in the structure. Because taller structures have lower resonance frequencies, the April quake’s low-frequency rumbles caused larger buildings to sway and crumble while largely sparing smaller dwellings, the researchers found.
The low frequencies resulted from the smooth and relatively long duration of the tectonic slipping that initiated the quake, the researchers propose. The low-frequency waves then echoed across the region and produced protracted violent shaking.
Determining where future low-frequency quakes will strike could save lives by identifying which building types are most vulnerable to collapse, says geologist Kristin Morell of the University of Victoria in Canada. “These are things that should be built into building codes.”
A new atlas of human genetic diversity reveals what human ancestors’ DNA may have looked like before people migrated out of Africa.
Ancestral humans carried 40.7 million more DNA base pairs than people do today, researchers report online August 6 in Science. That’s enough DNA to build a small chromosome, says study coauthor Evan Eichler, an evolutionary geneticist at the University of Washington in Seattle.
Human ancestors in Africa jettisoned 15.8 million of those DNA base pairs — information-carrying building blocks of DNA often referred to by the letters A, T, G and C — before dispersing around the globe, the researchers discovered. As people left Africa and spread to other continents, they dropped more chunks of DNA. Eichler and colleagues have followed these genetic bread crumbs to map relationships among 125 human groups worldwide. People didn’t just lose DNA. They also gained some. Compared with chimpanzees and orangutans, people have 728 extra pieces of DNA created when portions of the human genetic instruction book, the genome, were copied. Everyone has at least three copies of those duplicated bits, although the exact number varies from person to person.
Previous maps of human genetic diversity have usually not marked the yawning chasms left by deletions or the new territory created by duplications. Most diversity maps have focused on single DNA base pair changes, often called single nucleotide polymorphisms, or SNPs. But all the SNPs together comprise only 1.1 percent of the genome. Duplications and deletions, collectively known as copy number variants, have shaped more than 7 percent of the human genome.
Story continues below infographic Because duplications and deletions involve larger swaths of DNA than SNPs do, their influence on human evolution may also be bigger. Both duplications and deletions have been implicated in shaping human characteristics, such as bigger brains (SN: 3/21/15, p. 16; SN: 4/9/11, p. 15).
But researchers “can’t answer the question yet of whether what makes us human is in what was lost or what was duplicated,” says David Liberles, a computational evolutionary biologist at Temple University in Philadelphia.
Eichler’s choice is clear. “Duplications rock,” he says. “They affect more base pairs in the human genome than any other type of variation.” Duplications span 4.4 percent of the genome, while deletions represent 2.77 percent. And duplications tend to involve genes, while deletions often fall in spaces between genes, the researchers found.
His team flagged many duplications as possible medical and evolutionary points of interest. For instance, some groups of people have up to six copies of CLPS genes, which encode pancreatic enzymes that may help reduce blood sugar levels. Some African groups carry duplications of genes that may protect against sleeping sickness caused by trypanosome parasites.
Another attraction is a very large duplication of about 225,000 base pairs that Papua New Guineans inherited from Denisovans, an extinct group of hominids related to Neandertals. The colossal hunk of DNA contains two microRNA genes. MicroRNAs are small molecules that help regulate protein production. Eichler and colleagues calculate that the original duplication happened about 440,000 years ago in Denisovans. It was passed to Papuans and some other Melanesians about 40,000 years ago when their ancestors interbred with Denisovans. Now, about 80 percent of Papuans carry the duplication. Eichler speculates that the duplication may have given Papuan ancestors some evolutionary advantage, although what that advantage might be isn’t known.
While the researchers make a compelling case that duplications and deletions may play an important role in evolution, the team has provided little evidence that copy number variants really determine trait differences between groups, says Edward Hollox, a human geneticist at the University of Leicester in England. “It’s almost a paper saying, ‘Look, isn’t this interesting?’ But why it’s interesting they haven’t quite gotten to the bottom of.” Still, Hollox says the map will point other researchers to parts of the genome where evolution may have left its mark.
Memory Transfer Seen — Experiments with rats, showing how chemicals from one rat brain influence the memory of an untrained animal, indicate that tinkering with the brain of humans is also possible.
In the rat tests, brain material from an animal trained to go for food either at a light flash or at a sound signal was injected into an untrained rat. The injected animals then “remembered” whether light or sound meant food. Update: After this report, scientists from eight labs attempted to repeat the memory transplants. They failed, as they reported in Science in 1966.
Science fiction authors and futurists often predict that a person’s memories might be transferred to another person or a computer, but the idea is likely to remain speculation, says neuroscientist Eric Kandel, who won a Nobel Prize in 2000 for his work on memory. Brain wiring is too intricate and complicated to be exactly replicated, and scientists are still learning about how memories are made, stored and retrieved.
Large-scale climate patterns that can impact weather across thousands of kilometers may have a hand in synchronizing multicontinental droughts and stoking wildfires around the world, two new studies find.
These profound patterns, known as climate teleconnections, typically occur as recurring phases that can last from weeks to years. “They are a kind of complex butterfly effect, in that things that are occurring in one place have many derivatives very far away,” says Sergio de Miguel, an ecosystem scientist at Spain’s University of Lleida and the Joint Research Unit CTFC-Agrotecnio in Solsona, Spain. Major droughts arise around the same time at drought hot spots around the world, and the world’s major climate teleconnections may be behind the synchronization, researchers report in one study. What’s more, these profound patterns may also regulate the scorching of more than half of the area burned on Earth each year, de Miguel and colleagues report in the other study.
The research could help countries around the world forecast and collaborate to deal with widespread drought and fires, researchers say.
The El Niño-Southern Oscillation, or ENSO, is perhaps the most well-known climate teleconnection (SN: 8/21/19). ENSO entails phases during which weakened trade winds cause warm surface waters to amass in the eastern tropical Pacific Ocean, known as El Niño, and opposite phases of cooler tropical waters called La Niña.
These phases influence wind, temperature and precipitation patterns around the world, says climate scientist Samantha Stevenson of the University of California, Santa Barbara, who was not involved in either study. “If you change the temperature of the ocean in the tropical Pacific or the Atlantic … that energy has to go someplace,” she explains. For instance, a 1982 El Niño caused severe droughts in Indonesia and Australia and deluges and floods in parts of the United States.
Past research has predicted that human-caused climate change will provoke more intense droughts and worsen wildfire seasons in many regions (SN: 3/4/20). But few studies have investigated how shorter-lived climate variations — teleconnections — influence these events on a global scale. Such work could help countries improve forecasting efforts and share resources, says climate scientist Ashok Mishra of Clemson University in South Carolina.
In one of the new studies, Mishra and his colleagues tapped data on drought conditions from 1901 to 2018. They used a computer to simulate the world’s drought history as a network of drought events, drawing connections between events that occurred within three months of each other.
The researchers identified major drought hot spots across the globe — places in which droughts tended to appear simultaneously or within just a few months. These hot spots included the western and midwestern United States, the Amazon, the eastern slope of the Andes, South Africa, the Arabian deserts, southern Europe and Scandinavia. “When you get a drought in one, you get a drought in others,” says climate scientist Ben Kravitz of Indiana University Bloomington, who was not involved in the study. “If that’s happening all at once, it can affect things like global trade, [distribution of humanitarian] aid, pollution and numerous other factors.”
A subsequent analysis of sea surface temperatures and precipitation patterns suggested that major climate teleconnections were behind the synchronization of droughts on separate continents, the researchers report January 10 in Nature Communications. El Niño appeared to be the main driver of simultaneous droughts spanning parts of South America, Africa and Australia. ENSO is known to exert a widespread influence on precipitation patterns (SN: 4/16/20). So that finding is “a good validation of the method,” Kravitz says. “We would expect that to appear.” In the second study, published January 27 in Nature Communications, de Miguel and his colleagues investigated how climate teleconnections influence the amount of land burned around the world. Researchers knew that the climate patterns can influence the frequency and intensity of wildfires. In the new study, the researchers compared satellite data on global burned area from 1982 to 2018 with data on the strength and phase of the globe’s major climate teleconnections.
Variations in the yearly pattern of burned area strongly aligned with the phases and range of climate teleconnections. In all, these climate patterns regulate about 53 percent of the land burned worldwide each year, the team found. According to de Miguel, teleconnections directly influence the growth of vegetation and other conditions such as aridity, soil moisture and temperature that prime landscapes for fires.
The Tropical North Atlantic teleconnection, a pattern of shifting sea surface temperatures just north of the equator in the Atlantic Ocean, was associated with about one-quarter of the global burned area — making it the most powerful driver of global burning, especially in the Northern Hemisphere.
These researchers are showing that wildfire scars around the world are connected to these climate teleconnections, and that’s very useful, Stevenson says. “Studies like this can help us prepare how we might go about constructing larger scale international plans to deal with events that affect multiple places at once.”
A close look at one protein shows how it moves molecular passengers into cells in the kidneys, brain and elsewhere.
The protein LRP2 is part of a delivery service, catching certain molecules outside a cell and ferrying them in. Now, 3-D maps of LRP2 reveal the protein’s structure and how it captures and releases molecules, researchers report February 6 in Cell. The protein adopts a more open shape, like a net, at the near-neutral pH outside cells. But in the acidic environment inside cells, the protein crumples to drop off any passengers. The shape of LRP2’s structure — and how it enables so many functions — has stumped scientists for decades. The protein helps the kidneys and brain filter out toxic substances, and it operates in other places too, like the lungs and inner ears. When the protein doesn’t function properly, a host of health conditions can occur, including chronic kidney disease and Donnai-Barrow syndrome, a genetic disorder that affects the kidneys and brain.
The various conditions associated with LRP2 dysfunction come from the protein’s numerous responsibilities — it binds to more than 75 different molecules. That’s a huge amount for one protein, earning it the nickname “molecular flypaper,” says nephrologist Jonathan Barasch of Columbia University.
Typically, LRP2 sits at a cell membrane’s surface, waiting to snag a molecule passing by. After the protein binds to a molecule, the cell engulfs the part of its surface containing the protein, forming an internal bubble called an endosome. LRP2 then releases the molecule inside the cell, and the endosome carries the protein back to the surface.
To understand this shuttle system, Barasch and colleagues collected LRP2 from 500 mouse kidneys. The researchers put some of the protein in a solution at the extracellular pH of 7.5, and some in an endosome-mimicking solution at pH 5.2. Using a cryo-electron microscope, they captured images of the proteins and then stitched the images together in a computer, rendering 3-D maps of the protein at both open and closed formations. The researchers suggest that charged calcium atoms hold the protein open at extracellular pH. But as pH drops due to hydrogen ions flowing into the endosome, the hydrogen ions displace the calcium ions, causing the protein to contract.
