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EW GLAUCOMA 48 by Maxine Lipner EyeWorld Senior Contributing Writer Targeting early-onset glaucoma have some viability long term, our idea is that you would use these as a drug to treat children or other indi- viduals who are confirmed to have mutations in myocilin," Dr. Lieber- man said. "As early as possible, you would try to intervene in the aggre- gation process." This would hope- fully curtail the early glaucoma disease process. "If we can prevent the aggregation from happening, then we can prevent cell death, which is the consequence of the aggregation; if we stop cell death, we keep the trabecular meshwork intact—the region of the eye that controls fluid flow," Dr. Lieberman said. "The reason that is important is because fluid flow is directly related to intraocular pressure and elevated pressure leads to optic nerve damage." If a drug becomes available that can restore myocilin's function, or at the very least prevent it from aggre- gating, Dr. Lieberman thinks that more people will likely undergo genetic testing for the condition. Such a drug would only work on those with mutated myocilin, she emphasized. Alzheimer's plaque similarity In a separate study, investigators from this same lab found the aggregate that the myocilin protein makes is similar to the plaque seen in Alzheimer's disease. "Their bio- physical features make them very hard to break up; those found in Alzheimer's disease are known to kill neurons," Dr. Lieberman said. Still, these are not exactly paral- lel, she said. The two compounds discovered for early glaucoma would not work in Alzheimer's disease because the proteins themselves are different, Dr. Lieberman explained. Yet there is some similarity. "When myocilin misfolds, it forms the same kind of structure that was first identified and charac- terized from the Alzheimer world— the amyloid," she said. This might give early glaucoma researchers a leg up in developing a treatment. "We could take com- pounds that people have tested for the Alzheimer protein and test them on our aggregates to see if they break up," Dr. Lieberman said. Overall, she believes the method used here is underutilized. "We are taking a protein-based approach to glaucoma that in my view has been minimized in a field that is focused largely on genetics," she said. Going forward, this may have broader implications. "Under certain experimental conditions, we can get the wild-type myocilin to form the same kind of amyloid fibroid aggregates that the protein with the mutation makes intracellularly," she said, adding that so far, however, the evidence for this is minimal. Still, investigators think it is possible that the protein aggregation is happening in the extracellular matrix directly under certain aging conditions such as pH imbalance or oxidative stress. "If we could establish that it were happening in any kind of animal model, it would suggest that this myocilin protein plays more of a role than previously thought," Dr. Lieberman said. "If it did, our com- pounds could help more people." EW Editors' note: Dr. Lieberman has no financial interests related to her comments. Contact information Lieberman: raquel.lieberman@chemistry.gatech.edu February 2011 July 2014 Unlike in a normal eye, in cases with early-onset glaucoma, fluid flow is deterred by inherited mutated myocilin protein strands, which clump together. Source: National Eye Institute An approach to preventing the disease F or the first time, molecules with the potential to block the accumulation of the inherited form of mutant myocilin that can lead to early-onset glaucoma have been identified, according to Raquel L. Lieberman, PhD, associate professor of chemistry and biochemistry, Georgia Institute of Technology, Atlanta. Early-onset glaucoma affects about 3% to 10% of all open-angle glaucoma cases, Dr. Lieberman said. With the disease, genetically inherited mutated myocilin protein strands prevent fluid flow out of the eye by clumping together, raising eye pressure, she explained. "There is no way to prevent the disease right now," she said. "There is only management of the elevated pressure." One of the challenges initially faced by investigators was that there was no test to tell whether possible drug compounds were hitting the mark. So Dr. Lieberman and fellow investigators developed one. In a study published in the February 2014 issue of ACS Chemical Biology, investigators were able to use this to look for drug targets. Testing new compounds The test involved mixing mutant myocilin with a fluorescent com- pound and then measuring the change in fluorescence emitted when the protein bound to another molecule. "We took a biophysical approach to create a fluorescence plate reader assay that would very quickly read out whether something was binding or not," Dr. Lieberman said. "When we did an initial screen, we tested about 1,000 compounds and got 14 hits." From there, they were able to narrow this down to two that looked the most promising, she said. "We established that they bound to the protein when it was in its folded form and then were able to show that those compounds prevented aggregation," Dr. Lieberman said. One compound is called apigenin and the other is GW5074. Investigators also checked whether the cells treated with com- pound were secreting the protein. "Normally this protein is in an extracellular matrix but when it aggregates, it stays inside the cell," she said. "We thought that if we were inhibiting aggregation, then we would expect to see more of the protein being secreted out of the cell and that's exactly what happened." These compounds were restor- ing the cellular trafficking of the mutant protein, which would have otherwise been sequestered and aggregated inside the cells. Dr. Lieberman plans to expand this approach to find other com- pounds that may be more potent than the apigenin and GW5074. She also expects to test the two compounds in animal models. From there the hope is that they will be clini- cally applicable. "Assuming that these compounds 48 Glaucoma_EW July 2014-DL_Layout 1 6/30/14 8:47 AM Page 48

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