Those who took introductory biology classes in school might remember various parts of the cell and their roles. But one of the things at work that many nonscientists may not have heard of is inosine triphosphate pyrophosphatase, or the ITPA protein.
To really, really simplify things, ITPA is an enzyme that acts as a housekeeper in cells, removing gunk that shouldn't be there.
The "gunk" is inosine, which is a normal metabolite that can convert into other compounds that mimic the "A" and the "G" of the "ATG and C" that make up DNA; cells can then mishandle the new material and plug it into DNA or RNA where it shouldn't be, explains Nick Burgis, chair of Eastern Washington University's Chemistry, Biochemistry and Physics Department.
While ITPA has been studied for decades, scientists in the early 2000s started identifying clinical variants of the ITPA protein and linking those with different health issues.
Essentially, people can have various ITPA deficiencies. A common one, called P32T, affects as much as 15% of the world's population and can interfere with how people's bodies react when getting treatment for certain cancers or organ transplants, Burgis says.
A far rarer but somewhat similar deficiency, structurally, is known as the R178C mutant, which can cause a lethal infantile encephalopathy — kids born with this mutation rarely live to age 8, and can struggle with seizures and basic functions like eating, he says.
Burgis and his colleague Yao Houndonougbo, a biochemistry professor at Eastern, have been studying these deficiencies for years.
In September, the two were awarded a $350,000 grant from the National Institutes of Health to continue their work and spend the next three years trying to find the missing puzzle piece (or pieces) to potentially fix the broken ITPA proteins. They'll search a bank of more than 300,000 molecules maintained at UCLA, in hopes of finding possible leads that could ultimately spawn pharmaceutical medical therapies.
"The idea is, both at P32T and R178C, they both have stability issues, so the proteins both vibrate more, and they can kind of fall apart," Burgis says. "Because both patient populations ... kind of have similar issues, we're hoping we can address both of them."
Though robots at the UCLA lab will help Burgis and his team of student researchers fill hundreds and hundreds of wells in testing plates with the various molecules next summer, 300,000-plus is still a daunting number of compounds.
That's why Houndonougbo, a computational chemist, will be doing the initial heavy lifting for the team, virtually. He'll plug the digitized version of UCLA's "Molecular Shared Screening Resource" compound library into software to see which molecules are most likely to hit the parameters they're seeking.
"I'll try to see the rank of the small molecule in terms of what we call free energy," Houndonougbo says. "Lower the free energy, better the binding."
Then, Burgis and the research students will spend a month at UCLA testing various options, starting with the ones Houndonougbo's program highlighted, and see if they can confirm the software picked good options. UCLA is also interested to see how the virtual screening works, Houndonougbo says.
"They've never done this type of screening on the [digital] library before," he says. "So they're just curious to know how well the library will behave."
In the lab, the chemical reaction Burgis and the student researchers will use will turn each of the wells various colors, depending on what's happening. The color they're looking for is a deep green, which indicates more phosphate is in that reaction.
The phosphate is a byproduct of the housekeeping activity that ITPA does, so its presence indicates the enzyme is working properly.
The remainder of the project will be spent analyzing all the data and writing up their results.
"The ultimate goal is to lead to a drug," Houndonougbo says.
"I've been doing the basic research since 1998, and it's time to do the applied research, and teaming up with Yao has just really made that possible," Burgis says. "Together, my biochemical work and his computational work really kind of hinted to us that we might be able to address this issue through a drug. ... We're pretty excited." ♦
