Tracing the start of COVID-19 in GA

At a time when COVID-19 appears to be receding in much of Georgia, it’s worth revisiting the start of the pandemic in early 2020. Emory virologist Anne Piantadosi and colleagues have a paper in Viral Evolution on the earliest SARS-CoV-2 genetic sequences detected in Georgia. Analyzing relationships between those virus sequences and samples from other states and countries can give us an idea about where the first COVID-19 infections in Georgia came from. We can draw Read more

Reddit as window into opioid withdrawal strategies

Drug abuse researchers are using the social media site Reddit as a window into the experiences of people living with opioid addiction. Abeed Sarker in Emory's Department of Biomedical Informatics has a paper in Clinical Toxicology focusing on the phenomenon of “precipitated withdrawal,” in collaboration with emergency medicine specialists from Penn, Rutgers and Mt Sinai. Precipitated withdrawal is a more intense form of withdrawal that can occur when someone who was using opioids starts medication-assisted treatment Read more

CROI: HIV cure report and ongoing research

The big news out of CROI (Conference on Retroviruses and Opportunistic Infections) was a report of a third person being cured of HIV infection, this time using umbilical cord blood for a hematopoetic stem cell transplant. Emory’s Carlos del Rio gave a nice overview of the achievement for NPR this morning. As del Rio explains, the field of HIV cure research took off over the last decade after Timothy Brown, known as “the Berlin patient,” Read more

semagacestat

Redirecting beta-amyloid production in Alzheimer’s

Pharmacologist Thomas Kukar is exploring a strategy to subtly redirect the enzyme that produces beta-amyloid, which makes up the plaques appearing in the brains of Alzheimer’s patients.

Thomas Kukar, PhD

Preventing beta-amyloid production could be an ideal way to head off Alzheimer’s, but the reason why a subtle approach is necessary was illustrated last year by disappointing results from a phase III clinical trial. The experimental drug semagacestat was designed to block the enzyme gamma-secretase, which “chomps” on the amyloid precursor protein (APP), usually producing an innocuous fragment but sometimes producing toxic beta-amyloid.

Gamma-secretase also is involved in processing a bunch of other vital proteins, such as Notch, central to an important developmental signaling pathway. Scientists suspect that this is one of the reasons why trial participants who received semagacestat did worse on cognitive/daily function measures than controls and saw an increase in skin cancer, leading watchdogs to halt the study.

While a postdoc at Mayo Clinic Jacksonville and working with Todd Golde and Edward Koo, Kukar identified compounds – gamma-secretase modulators or GSM’s — that may offer an alternative.

“We are looking at a strategy that’s different from global gamma-secretase inhibition,” he says. “The approach is: don’t inhibit the enzyme overall, but instead modify its activity so that it makes less toxic products.”

Gamma-secretase chomps on amyloid precursor protein, and how it does so determines whether toxic beta-amyloid is produced. It also processes several other proteins important for brain function.

This line of inquiry started when it was discovered that some anti-inflammatory drugs also could reduce beta-amyloid production. Then, the crosslinkable probes Kukar was using to identify which part of the gamma-secretase fish was doing the chomping ended up binding the bait (APP). This suggested that drugs might be able to change how the enzyme acts on one protein, APP, but not others.

Now an assistant professor at Emory, he is examining in greater detail how gamma-secretase modulators work. Two recent papers he co-authored in Journal of Biological Chemistry show 1) how the proteins that gamma-secretase chews up are “anchored” in the membrane and 2) how selective GSM’s can be on amyloid precursor protein.

Although clinical studies of a “first generation” GSM, tarenflurbil, were also stopped after negative results, Kukar says GSM’s still haven’t really been tested adequately, since researchers do not know if the drugs are really having an effect on beta-amyloid levels in the brain. Newer compounds coming through the pharmaceutical pipeline are more potent and more able to get into the brain. While looking for more potent GSM’s is critical, Kukar says it’s equally as important to understand how gamma-secretase works to understand its biology.

Posted on by Quinn Eastman in Neuro Leave a comment