We should be melting | Interview with Dr. Nancy Forde

0:00:15.1Collagen

Jed Macosko: Hi, this is Dr. Jed Macosko at Wake Forest University and Academic Influence. And today we have an old dear friend of mine, Professor Nancy Forde from Simon Fraser University, which is up in British Columbia in Canada, and we’re so glad that you could make it here with us today, and I am fascinated that you have gone beyond just molecular motors and molecular machines to study the most plentiful protein in animals, which is collagen. So tell us a little bit about collagen and why we should care about it.

Nancy Forde: Sure, so as you rightly said, collagen is the most abundant protein in animals and humans, we are, I suppose, animals. And it makes up all sorts of different materials in our bodies, our connective tissues like bone, where it forms with minerals and tendons and ligaments and cartilage, and skin, our lens of our eyes, it forms the what’s called extra-cellular matrix that surrounds our cells and gives them important sort of information about what to do. And what I find really interesting is that somehow we get all of these diverse structures and materials from this protein that has a very unique structure, so it’s a triple helix, which means sort of you picture DNA as two strands are wrapping around each other with collagen there’s three strands that wrap around each other to form these very long, thin thread-like structures.

And in those they have encoded this ability to stick to their neighbors in a very specific way and form higher order structures. So the analogy I like to give is, if you think about taking a short piece of thread and taking more pieces of thread and sort of wrapping them together, you could make twine, and then you take that twine and you wrap it and then you can make a sort of a piece of a rope, and you take that and you get a rope, and so you picture a sailors rope, which is super strong and thick and sturdy, but it’s made up of these tiny little threads, and it’s very much the same with a lot of our tissues, like our tendons, 99% collagen, these tiny little threads that just know how to organise, they have this encoded in them to form these release stable structures.

Jed: That is so cool. So when you say that it’s encoded, we all know that protein is made up of amino acids, and there must be certain amino acids in these collagen and structures that first of all, tell them how to twist together in the groups of three. But how do they know how to attach side to side to other threads? How does that work?

Nancy: Yeah, so that’s something that we’re still figuring out, there’s certainly... It’s very much encoded in those amino acids, and a large part of that has to do with the charge profiles, so different amino acids can have positive charges or negative charges, and so if they come to a neighboring strand, they can line up with these opposite charges attracting and bind in a particular way, there’s other more subtle interactions as well, such as wanting to have water out of the way and keeping oily or hydrophobic groups near each other, but it is an ongoing question as to how the different types of collagen can perform these different types of fibrils and how they know only to pair with like collagens and not other ones that are very similar, but not the same.

Jed: Awesome, so why is it important that a certain type of collagen maybe from, I don’t know, like tendon, doesn’t pair together side by side with a different kind of collagen? Maybe you can explain a little bit about the types of collagen and why is it important that they don’t miss match.

Nancy: Yeah, so I think the different types are expressed and produced by cells in different tissues and in different times during development too, so the types of collagen you get will change during the fetal stage versus the adult stage, for example. And they will form these different types of structures. So the rope-like structures that I was talking about, there is a number of collagens that will form those, but there’s different collagens, like, type 4, for example, forms like a mesh-like network, and so they don’t tend to stick side to side as much, they tend to stick more head-to-head, and tail-to-tail.

And those form filtration barriers, the kidney, for example, that allow it to perform its filtration tasks. So you wanna have the right types of collagen produced by cells at the right time, and then they want to assemble into the correct structures to perform their functions. We also know that the mechanics of those provide important information that feeds back to the cells that surround them and tell them, "Hey, yeah, this is a bone environment," versus, "This is a fat cell environment," and so on. So there’s a lot of intricacies that we’re tying to figure out.

0:05:34.2The individual triple helix structure of collagen

Jed: And what about your lab allows you to probe these intricacies, what kind of equipment and mathematical fire power do you have to help out in this way?

Nancy: So we’re really focused on the molecular level, which is the individual triple helix structure of collagen, and we want to look one molecule at a time and figure out about its stability and mechanics. So interestingly, if you take collagen and you start to heat up the surrounding, so you have, let’s say just in some water or something, and you start to heat that up, you get to around 37 degrees or body temperature and that’s when it starts to fall apart. And this has been known for a long time, that various organisms, their collagens melting temperature, the so-called the temperature which they start to fall apart is very close to body temperature, and so cold-blooded species have collagen that will melt at a lower temperature than ours for example.

And what was discovered a number of years ago now is that it’s actually below body temperature that it will fall apart, and so we have these fundamental building blocks in our tissues, and they’re not stable at body temperature, which is just so mind blowing. Why are we not just puddles on the floor, right? And so it turns out that once they’ve stuck to other proteins that made these higher order structures that stabilises them, but something about their molecular structure is very much on the cusp of stability, which I think is what gives collagen a remarkable ability to respond to its environment and to maybe act as a signal to cells, for example, how much forces that are stretching on this.

So we’ve been developing a number of characterisation techniques using sometimes commercial instruments like an atomic force microscope or AFM to be able to trace out the contours of these proteins. We’ve built optical tweezers instruments that use focused laser beams that allow us to exert force on particles and then be able to stretch collagens that are tethered between them, and most recently, we’ve built an instrument called the centrifuge force microscope, which is a small compact wireless microscope that cost 500 bucks, and you put it in the bucket of a centrifuge and turn that on, and it spins around like being on one of those swing rides at the fair grounds. Right, and that allows us to then do very high throughput force measurements because everything in that microscope is feeling this force and we can image what’s going on and get data on thousands of molecules.

0:08:20.9Sign off

Jed: Fascinating. Well, this has just been so incredible, and I hope everybody can get excited about collagen the way you and your lab have gotten excited about it because of the amazing things you’ve told us about today. So thank you for taking some time to talk a little bit about your research, bring us upto date in some of the new discoveries about collagen. So thank you so much, Nancy.

Nancy: Well, thank you for your interest. It has been really fun.