Glyco-what?

The dreaded question for this graduate student: “What do you do?” Ugh. Must I really talk about my research at the dinner table or in this dimly lit bar? Perhaps it’s my leaning towards introversion, but this really is my least favorite question to answer outside of a strict research setting. It’s inevitable though. Here’s how this conversation typically goes:

Other Person: “What do you do for a living?”

Me: “I’m a graduate student in the biochemistry department.”

Other Person: “Oh, cool. What do you study?”

Me: “The glycosylation of…”

Other Person: “Glyco-what?”

My sentiments exactly. Why am I using fancy words to describe something that’s pretty straightforward? Probably because that gin and tonic is calling my name or I want to stuff my face with some fries… but, in all honesty, my elevator pitch could use some serious work. What I work on is hella cool and related to a slew of human diseases, so I should be jumping at the chance to tell people about it, even if they’re standing between me and a tasty smorgasbord of food. So, let’s reimagine this typical conversation.

Glycosylation – what is it?

Let’s start at the beginning. Similar to how architects first draft blueprints to build a house, life begins with a blueprint, our DNA. These blueprints are written out into useful instructions similar to how our DNA is transcribed into RNA. With a set of building instructions sent off to contractors, construction can finally begin. Likewise, once RNA transcripts exit the control center of our cells, they arrive in the hands of our cell’s contractors, the ribosomes. The ribosomes build the final product: proteins. This template-driven process of DNA to RNA to protein (or blueprints to instructions to house) is what scientists call the central dogma of biology.

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The central dogma: DNA → RNA → Protein. Photo Credit to Philippe Hupé

The house blueprints dictate structure, but what determines details like the color of the doors or shutters? The colors might depend on the selection of paint available at the nearest home improvement store or what the best deal of the day is. In this scenario, the color of a home and the finishing touches are not defined by the template or blueprint. Similarly, modifications to built proteins are not directly encoded in the DNA template. These alterations can vary from protein to protein just like color can vary from house to house. So what are these alterations to proteins, and how do they arise?

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In the central dogma, DNA is the blueprint of our cells. Photo Credit to Cameron Degelia

A lot can happen to a protein to fine tune or alter its function, but there is one type of modification (in my personal opinion) that’s sweeter than the rest: glycosylation. Glycosylation is just a fancy word for the process of coating proteins with sugars. Yes, sugars – I told ya it was sweet! Speaking of sweet, can you please pass the sweet potatoes?

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Photo Credit to Adam Engelhart

Unlike the template driven DNA → RNA → protein process, the guidelines for this sugar coating of proteins is less set in stone. Instead, the sugar coating is at the mercy of other proteins in the cell called enzymes. These enzymes are responsible for linking sugar building blocks to proteins, similar to how painters are responsible for coating a house in your favorite color.

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Glycosyltransferases are the enzymes that install sugars on proteins, kinda like how painters cover the exterior of a house with paint. Photo Credit to Ron Cogswell

Glycosylation – why should we care?

This sugar coating of proteins enables our cells to stick together and form tissues. They regulate cell-cell interactions and binding, and they even mediate interactions between different organisms (think HIV and human host). Sugars can also act as switches inside our cells to regulate various functions. So when something goes wrong with glycosylation, the effects can be devastating and widespread like in the progression to metastatic cancer. In fact, there is a whole subset of human diseases caused by glycosylation disorders. Understanding how and why these disorders occur will help us better prevent and treat disease. There’s an entire field of science dedicated to this research called glycobiology, and I’m pretty proud to be a member of the team. Who knew sugars could do so much and play such an important role in life?

About the author:

Stephanie HalmoStephanie M. Halmo is a former middle school science teacher turned graduate student, actively pursuing her Ph.D. in biochemistry from the University of Georgia. In her spare time she likes to dance, volunteer at local schools and tie-dye anything she can get her hands on. She is currently ASO’s News Editor. You can connect with Stephanie on Twitter and Instagram @shalmo or by email: shalmo27@uga. More from Stephanie M. Halmo.