Sugary handshakes are how cells talk to each other − understanding these name tags can clarify how the immune system works
Unlike people, cells perform these handshakes using the diverse range of sugar molecules coating their surface like trees covering a landscape.
- Unlike people, cells perform these handshakes using the diverse range of sugar molecules coating their surface like trees covering a landscape.
- Handshakes between these sugar molecules, or glycans, trigger cells to react in specific ways toward each other, such as escape, ignore or destroy.
What are glycans?
- The vast number of possible glycan structures that can be built from connecting these sugar molecules together allows glycans to store rich information.
- Glycans are chemically bonded to proteins and lipids on the surface of red blood cells.
- Notably, the surface of type A red blood cells have glycans that differ from the glycans on the surface of type B and type O red blood cells.
- For example, distinctive glycoproteins cover the surface of the viruses that cause COVID-19, HIV and H1N1 influenza and help them infect cells.
- Glycolipids also coat many bacteria, allowing them to stick to their hosts and protect them from viruses and immune cells.
How do cells read glycans?
- Found on surfaces of certain immune cells, these lectins deliver the glycans to proteins on other immune cells that can now selectively destroy any viruses or cells that carry that glycan.
- For example, these lectins recognize glycans on the surfaces of cancer cells and direct other immune cells to eliminate these cancer cells.
- Another type of lectin called siglecs are found on surfaces of immune cells and help them distinguish self from nonself, that is, between the cells that make up the body and the cells that are foreign to the body.
- The bacterial glycans in the vaccine trigger an immune response when immune cells recognize the glycans as foreign threats.
Examining every sugar molecule
- Comprehensively extracting all the information stored in glycans is very difficult because there isn’t currently technology able to analyze the complex and diverse structures of glycans.
- Individual glycans are composed of sugar molecules in unique arrangements, but current analytical tools can only simultaneously analyze many glycans.
My lab is confronting this challenge by developing imaging technology that can analyze the structure of glycans by imaging each individual molecule. Essentially, we’re developing a technique to open the jar and study every single candy one at a time. In the long run, my team aspires to unveil how these glycans present themselves to the proteins that recognize them and, finally, reveal the very language that cells use to express themselves.
Kelvin Anggara works for the Max Planck Institute for Solid State Research and receives funding from the European Research Council under Project GlycoX (101075996).