Earthworms live in the caterpillar’s intestines, and bioluminescent bacteria lurk inside the worms. Photolabdus asymbioticaCaterpillars glow in the dark. But this nesting doll-like setup has another, more detrimental effect. The bacteria secrete lethal molecular syringes 100 nanometers in length that get caught in insect cells. A syringe attached to the cell pushes a spear of molecules through the cell’s membrane that releases a toxic payload. When the insect host dies and decomposes, the bacteria escape and colonize the next victim.
In a paper published today in Nature, Researchers Report Modifications photolabdasThe syringe, called the contraction injection system, attaches to human cells allowing them to inject large proteins. This research could provide a way to deliver a variety of therapeutic proteins to all types of cells, including proteins that can “edit” a cell’s DNA. “It’s a very interesting approach,” says Mark Kay, a gene therapy researcher at Stanford University who was not involved in the study. “I think it will be very useful if we want to express proteins that can do genome editing,” he says, to correct or knock out genes that are mutated in inherited diseases.
Nanoinjectors may be an important tool for scientists interested in fine-tuning genes. Feng Zhang, a molecular biologist at the Massachusetts Institute of Technology’s McGovern Brain Institute and the Broad Institute at the Massachusetts Institute of Technology and Harvard, and an investigator on the study, said: Zhang is known for developing the gene editing system CRISPR-Cas9. Existing techniques allow the editing mechanism to be inserted into several tissues such as the blood, liver and eyes, but there is no good way to reach other locations such as the brain, heart, lungs and kidneys. It is also promising for the treatment of cancer because it can be engineered to attach to cancer cell receptors.
Zhang was looking for new ways to deliver gene-editing enzymes to cells. Two years ago, Zhang and his graduate student Joseph Kreitz photolabdasinjection system. This system was unique in that it was adapted for insect cells. “This is he one of the very rare instances in which a bacterium is injected into an animal cell rather than another bacterial cell,” he says. “We thought that if we could inject this into animal cells, it might work in human cells as well.”
Researchers mass-produced miniature syringes by inserting the syringe’s genetic blueprint. Escherichia coli bacteria.of Escherichia coli It faithfully secreted tiny syringes that, when exposed to insect cells, bound to them and injected the toxin as expected. . “So we had to figure out how to design this,” says Zhang.
Zhang’s team focused on the tentacle-like structures of the injector, called tail fibers, that grip and hold the cell before the injector pierces the cell’s membrane. The researchers tweaked these fibers in more than 100 different ways, allowing them to hook onto human cells. nothing worked. Then, about a year into the project, a newly released version of artificial intelligence software called AlphaFold came to their rescue. AlphaFold predicts protein conformations from amino acid sequences. His three-dimensional view of the tail fiber protein helped the team understand how to modify it to adhere reliably to human cells.
In one experiment, the researchers were able to attach a nanosyringe with modified tail fibers to the epidermal growth factor receptor (EGFR) on the surface of some human cancer cells. Loading the injection system with the toxin killed nearly all cells with receptors but spared others, demonstrating its specificity. Researchers have adjusted the tail fibers of the injector so that it can also recognize surface markers on other cell types.
Zhang’s team also found that the system could be packed with different protein payloads by adding tags to the proteins that mark them as ammunition that should be loaded into the syringe needle. Scientists have attached this tag to the protein toxin and gene-editing enzyme Cas9. Cas9 is a large molecular scissor that cuts DNA at locations dictated by molecules that direct the scissors to the correct location. When these proteins were delivered to human cells, they either killed the cells or edited the cells’ genes. “We show that different types of proteins can be loaded onto these needles simply by tagging the proteins,” Zhang said. Each needle can also be loaded with multiple copies of the protein for increased dosage, says Zhang.
To further explore the technology, the researchers again used AlphaFold to design these tiny syringes to bind to mouse cells and inject them into mouse brains. So we inserted a protein into the neuron that makes the cell glow. “It’s important to understand that there are a number of ways in which this can be done,” said Rodolphe Barrangou, a geneticist at North Carolina State University who studies CRISPR-Cas but was not involved in the new study. study.
However, the technology is still in its very early stages. Zhang plans to experiment with non-protein payloads such as DNA and RNA, as well as increase their efficiency as delivery devices. In the future, Kay says, it will be important to test the technology in “higher mammals.” “There are a lot of things that work well in mice and small mammals that don’t work well in nonhuman primates and humans,” he adds. Injection systems are also composed of bacterial proteins, which may also lead to immune responses in humans. “We need to know: How immunogenic is it when administered to humans?” Zhang says.
Still, the study shows the importance of biological inspiration for solving tough technical problems in biology and medicine, says Barrangou. “This is a very good example of a focus on unearthing items of interest from natural biological dark matter that is both practical and deployable,” he says.
