Carbohydrate-binding proteins fill in gaps in immune defenses
Our bodies produce a family of proteins that recognize and kill bacteria whose carbohydrate coatings resemble those of our own cells too closely, scientists have discovered.
Called galectins, these proteins recognize carbohydrates from a broad range of disease-causing bacteria, and could potentially be deployed as antibiotics to treat certain infections. The results are scheduled for publication in Nature Chemical Biology.
Researchers at Emory University School of Medicine made the discovery with the aid of glass slides coated with an array of over 300 different glycans (carbohydrates found on the surfaces of cells) derived from bacteria, many of which are found in the intestine. One can think of these slides – called microbial glycan microarrays – as wardrobes displaying a variety of clothes worn by gut bacteria.
"Many microbes cover themselves with glycans that somewhat resemble our own cells," says Richard D. Cummings, PhD, professor and chair of the Department of Biochemistry at Emory University School of Medicine. "That limits how well the immune system can use antibodies to respond to those microbes."
To prevent auto-immune attack, our bodies usually don't make antibodies against molecules found on our own cells. That leaves gaps in our defenses that bacteria could exploit. Several of those gaps are filled by galectins, the researchers found.
The discovery expands upon an initial finding, published in Nature Medicine in 2010, describing galectins that recognize and kill bacteria that express the human blood group B antigen.
The Emory researchers collaborated with the laboratory of James C. Paulson, PhD, at the Scripps Research Institute (TSRI). Co-first authors of the paper are Sean Stowell, MD/PhD (a resident in in laboratory and transfusion medicine at Emory), Connie Arthur, PhD (postdoctoral fellow at Emory with Stowell), and research assistant Ryan McBride at TSRI.
In contrast to antibodies, the galectins kill the bacteria directly, without needing other parts of the immune system to pile on. The researchers identified several varieties of bacteria (Pseudomonas aeruginosa, Providencia alcalifaciens, Klebsiella pneumoniae, and Serratia marcescens, for example) targeted for killing by galectins. In some cases, only certain strains of a given bacteria were vulnerable, because only those strains carried the target glycan.
"These studies have opened the way to understanding the ways in which adaptive or antibody-based factors work together with innate or galectin-based factors to give us immunity against a broad range of microbes," Cummings says.
In addition, the microarray technology provides tools to study glycan-binding antibodies and galectins in populations, he says.
"These studies use tiny amounts of blood – just a few drops – and show how glycan microarrays could supersede previous technology," he says. "Using these tools, investigators could identify developmental- and age-specific differences in anti-microbial glycan antibodies in humans, which may predict susceptibility to disease."
Quinn Eastman | Eurek Alert!
New Computer Model Could Explain how Simple Molecules Took First Step Toward Life
29.07.2015 | Brookhaven National Laboratory
Switch for building barrier in roots
29.07.2015 | The University of Tokyo
Researchers have developed an ultrafast light-emitting device that can flip on and off 90 billion times a second and could form the basis of optical computing.
Joint BioEnergy Institute study identifies bacterial protein that is key to protecting rice against bacterial blight
A bacterial signal that when recognized by rice plants enables the plants to resist a devastating blight disease has been identified by a multi-national team...
Researchers in the Cockrell School of Engineering at The University of Texas at Austin are one step closer to delivering smart windows with a new level of energy efficiency, engineering materials that allow windows to reveal light without transferring heat and, conversely, to block light while allowing heat transmission, as described in two new research papers.
By allowing indoor occupants to more precisely control the energy and sunlight passing through a window, the new materials could significantly reduce costs for...
Argonne scientists used Mira to identify and improve a new mechanism for eliminating friction, which fed into the development of a hybrid material that exhibited superlubricity at the macroscale for the first time. Argonne Leadership Computing Facility (ALCF) researchers helped enable the groundbreaking simulations by overcoming a performance bottleneck that doubled the speed of the team's code.
While reviewing the simulation results of a promising new lubricant material, Argonne researcher Sanket Deshmukh stumbled upon a phenomenon that had never been...
A NASA camera on the Deep Space Climate Observatory (DSCOVR) satellite has returned its first view of the entire sunlit side of Earth from one million miles away.
The color images of Earth from NASA's Earth Polychromatic Imaging Camera (EPIC) are generated by combining three separate images to create a...
23.07.2015 | Event News
10.07.2015 | Event News
25.06.2015 | Event News
29.07.2015 | Physics and Astronomy
29.07.2015 | Life Sciences
29.07.2015 | Awards Funding