“It is much more important to identify Where This medication works because you don’t want to end up blindly participating in a human or animal experiment, ”says Jason Kindrachuk, a microbiologist at the University of Manitoba who is not involved in the research. The approach is by no means a guarantee, but it is a good way to generate leads that researchers can investigate further. “All of this information is amazingly useful,” he says.
The new UCSF-led research takes a slightly different approach. This time they measured changes in an activity called phosphorylation, which plays a role in turning cellular processes on and off: from the way the cell grows, divides, and dies, to the development of filopodia. The activity is managed by a type of protein called kinases. The researchers infected cells from African green monkeys, known for their high susceptibility to SARS-CoV-2, and used mass spectrometry to study how phosphorylation changed over time. They then mapped the activity on analog kinases in human cells and found significant changes in 49 of them.
Some of the pathways affected appeared to be intuitive and inhibited cell processes such as division and apoptosis or cell death. “It̵
The next task was to find drugs that block the misbehaving kinases. “What is so great is that there are so many different drugs that work against them,” says Krogan. Many of the team’s candidates were cancer drugs designed to suppress cellular processes that have become confused. To get them, Krogan turned to a UCSF colleague, chemist Kevan Shokat. “You go into his freezer and you can find an inhibitor for every kinase. And if he doesn’t have it, he knows how to get it, ”he says.
Employees in Paris and New York then tested 68 compounds known to inhibit kinases and looked for ones that could eliminate the virus in a dose that did not kill the monkey cells. In this regard, most have failed the pattern. But six or seven of the compounds, Krogan says, were particularly promising, including a handful that were “more effective than Remdesivir” and used as a control.
Among them was a compound called silmitasertib, which inhibits a kinase called CK2 and is being tested as a cancer drug. The researchers had already identified it in its predecessor nature Study based on protein interactions. In the course of this research, they also discovered interesting structures that originate from the infected cells. They turned to even more employees – this time at the University of Freiburg in Germany and at the Rocky Mountain Labs in Montana – to image the infected cells in more detail using electron microscopes. Then they found these unusually spindle-shaped filopodia along with clusters of both the virus and CK2.
“It’s exciting, but provisional,” says Jenny Gallop, a biochemist at Cambridge University who studies filopodia. Since her own laboratory was temporarily closed due to the pandemic, she searched the internet for signs that filopodia could play a role in SARS-CoV-2. She had reason to believe that they could. Viruses, including Marburg and Ebola, have been found to kidnap Filopodia and force them to grow longer, branch, and carry virus particles to their neighbors. The mechanism is particularly well studied in another virus called vaccinia, which has been found to play a role in the “spread” of the virus from one cell to another.
The difficulty, says Gallop, is that imaging tiny filopodia is a tedious process. The level of detail that the researchers have achieved in a short time is no small matter, but further experiments and imaging procedures are required to confirm whether the researchers have identified the correct mechanism. CK2 is an important kinase that plays a role in many cell processes. Other kinases also play a role in the development of filopodia. A next logical step to strengthen the compound would be to see whether silmitasertib as a CK2 inhibitor actually limits the growth of filopodia in infected cells.