Columbia Scientists Solve 47-Year Mystery of Malaria Invasion, Design First Invasion-Blocking Mini-Protein
核心洞察
Researchers at Columbia University captured the first high-resolution 3D structure of the malaria (搜索) parasite's moving junction, revealing it actively remodels host cell membranes rather than serving as a passive doorway.
The structure, described as sailboat-shaped with AMA1 (搜索) forming the "sail" and RON proteins the "hull," uses positively charged anchors and wedge-like helices to deform and penetrate the red blood cell membrane.
Using the structure as a blueprint, the team designed a mini-protein inhibitor that blocks parasite invasion in a dose-dependent manner without affecting already-infected cells, offering proof of concept for a new class of antimalarials.
For nearly half a century, the moving junction—a ring-shaped structure malaria (搜索) parasites use to force their way into human red blood cells—has remained one of the most tantalizing and stubborn mysteries in parasitology. Now, a team at Columbia University has not only solved its structure at atomic resolution but has also used that blueprint to design a mini-protein that blocks invasion, a proof of concept for an entirely new kind of antimalarial drug. The findings were published today in Cell.
The work overturns a decades-old assumption: rather than a passive doorway the parasite hauls itself through, the moving junction is a molecular machine that actively remodels the host cell's membrane to lever the parasite inside. "It had been pictured as a kind of series of staples or spot-welds, making up a passive ring the parasite hauls itself through," said Meseret Haile, the study's first author and a PhD candidate in the lab of Chi-Min Ho. "What we see instead is a machine built to reshape the host cell's own membrane. That changes how we think about the whole event."
A structure that vanishes in under a minute
The moving junction has been a puzzle since 1978, when scientists first observed a mysterious thickening of the membrane where parasite meets cell in electron microscopy images. Researchers eventually identified the four parasite proteins that assemble into the junction's basic building block—AMA1 (搜索), RON2 (搜索), RON4 (搜索), and RON5 (搜索)—and confirmed that all were essential for invasion. But the structure assembles, does its job, and dissipates in roughly 60 seconds, making it extraordinarily difficult to capture.
The Columbia team got around this by stopping invasion mid-stride. Using a compound that halts the parasite's internal motor without preventing the junction from forming, they stalled parasites partway into red blood cells, extracted the fully assembled AMA1 (搜索)-RON complex, and imaged it with cryo-electron microscopy. The result was a sharp, three-dimensional view strikingly shaped like a sailboat: the AMA1 protein forms a "sail" above the cell surface, while the three RON proteins form a broad "hull" pressed against the membrane below.
A membrane-remodeling machine, not a passive ring
The biggest surprise lay in the hull. The face of the structure pressed against the host membrane is blanketed with positively charged anchors, and the surface is studded with short helices that drive deep into the membrane like wedges—both widely recognized hallmarks of cellular machines that bend and reshape membranes.
To test whether the structure could indeed deform a membrane, the researchers synthesized the parasite's wedge-like helices and added them to artificial membrane bubbles. The membranes thinned and punctured. Weakened versions of the helices left the bubbles intact. The team concluded that the moving junction pulls the host membrane into shape, likely working in concert with the parasite's motor to lever the parasite inside.
"We've known for decades that this structure is essential for the parasite to get into a cell, but not how it actually works," said Chi-Min Ho, assistant professor in the Department of Microbiology and Immunology at Columbia University Vagelos College of Physicians and Surgeons and the study's senior author. "Pulling it directly out of the parasite intact let us finally ask that question directly."
From structure to therapeutic blueprint
Beyond revealing mechanism, the structure gave the team a precise map of where and how AMA1 (搜索) grips its partner protein—the contact that holds the entire junction together. Using a machine learning-powered protein-design tool together with their structural information, the researchers designed a mini-protein to break that grip.
Their best candidate blocked parasites from invading red blood cells in a dose-dependent manner and left already-infected cells unaffected, confirming that it works specifically by stopping entry rather than through general toxicity. "Once we could see the target in its real setting, designing something to block it became a tractable problem," said Daphne Kaxiras, an MD-PhD student in Ho's lab who led the inhibitor design. "That's the part we're most eager to build on."
The designed mini-protein is a first proof of concept, not a drug, and will need considerable refinement before it could be tested in people. But it demonstrates a new strategy: using near-native structures to design invasion-blocking mini-proteins against a target that has long frustrated conventional approaches. The same structure also clarifies how several leading anti-malaria (搜索) antibodies work, information that could feed back into vaccine design.
The stakes: 600,000 deaths and rising resistance
Malaria (搜索) still kills roughly 600,000 people a year, the overwhelming majority of them young children in sub-Saharan Africa, and the parasite is steadily becoming resistant to frontline drugs. The disease starts with a single event—a parasite breaking into a red blood cell—and in an infected person, trillions of parasites are released and invade every 48 hours in synchronized waves, driving the periodic fevers characteristic of the disease.
The same moving junction machinery is used across every species and every stage of the parasite's life cycle, which has made it one of the most sought-after targets in malaria (搜索) research. Block it, and you stop infection at its source. The team's approach—imaging fragile complexes captured directly from the organism and using them to guide design—may also apply to many other parasites and pathogens that are notoriously difficult to study.