Published by the Students of Johns Hopkins since 1896
October 4, 2022

Hopkins scientists discover new kinase that may play key role in neurodegenerative diseases

By NIRANJAN BEHERA | May 2, 2021



The scientists discovered that PKC delta is not a direct kinase of eIF2α but rather an enzyme that phosphorylates microtubule affinity-regulating kinase 2 (MARK2), which itself turned out to be a direct kinase of eIF2α.

Scientists from the School of Public Health’s Department of Biochemistry and Molecular Biology discovered a kinase of eukaryotic initiation factor 2 alpha (eIF2α) that may play a critical role in translation regulation for neurodegenerative diseases such as ALS.

10 years ago, Dr. Sarah Kavianpour, then a master’s student at the School of Public Health, joined the lab of Dr. Jiou Wang, a professor of biochemistry and molecular biology.

Upon Kavianpour’s arrival, Wang granted her the opportunity to work alongside a visiting scholar in his lab, Xumei Zhang, who was researching how misfolded proteins regulate protein synthesis. At this time, Zhang was looking into the four known kinases of eIF2α. Particularly, she looked at protein kinase RNA-like endoplasmic reticulum kinase (PERK), which is known to be involved in protein stress and plays a role in decreasing translation when proteins are misfolded in the endoplasmic reticulum (ER).

In an interview with The News-Letter, Wang explained what prompted the lab to search for a new kinase for eIF2α.

“Previously, people thought that... even if there is proteotoxic stress outside the ER, [it] will affect the protein homeostasis inside the ER, eliciting the unfolded protein response, which is true,” he said. “There’s always this cross-talk between different compartments in the cell.” 

When looking at denatured proteins in the cytoplasm, Wang suspected that another kinase that handles cytoplasmic protein misfolding might exist. Since Zhang would soon leave her project, Wang suggested that Kavianpour extend Zhang’s research and begin searching for a potential new kinase involved in the phosphorylation of eIF2α.

According to Kavianpour, she embraced this opportunity. Wang provided her with a list of a few candidates from an existing dataset of potential kinases to aid in her search. 

Finding such a kinase was not easy. Kavianpour recalled reading scientific literature carefully and extensively to familiarize herself with the potential kinases. In addition, proteins often have more functions than they are named after.

Kavianpour described discovering a pattern in an interview with The News-Letter. 

“I had looked at them enough [that] they had all been subconsciously in my mind [and] I was able to put together a connection,“ she said. 

That pattern was the enzyme protein kinase C delta (PKC delta). Not only was it present in the signal cascades of the four known kinases, but it was also there in the pathways of many of the potential candidates. She hypothesized and then was able to show that PKC delta is involved in the regulation of eIF2α phosphorylation.

However, the search for the new regulatory pathway of eIF2α phosphorylation was more complicated than expected. The scientists discovered that PKC delta is not a direct kinase of eIF2α but rather an enzyme that phosphorylates microtubule affinity-regulating kinase 2 (MARK2), which itself turned out to be a direct kinase of eIF2α.

By this point, Kavianpour was preparing to apply to medical school. Yu-Ning Lu, a student and later postdoctoral fellow, began to work on the project.

Because it was widely thought that only four direct kinases of eIF2α existed, the researchers wanted to make a thorough collection of evidence before concluding that MARK2 was a previously unknown fifth kinase. Lu made critical contributions to the large body of work that led to this discovery in the next few years.

To establish that MARK2 was not an indirect kinase of eIF2α, he had to take on many challenging experiments in systems using either purified proteins or genetically engineered cells.

For example, Lu conducted an experiment to determine whether MARK2 still phosphorylates eIF2α in cells under proteotoxic stress with all four known direct kinases removed. To do this, he built cells without the aforementioned kinases and showed that MARK2 can still act independently.

In an email to The News-Letter, Lu discussed the value of perseverance in his work and in the field of science. 

“This study took us many years to complete. What I learned through this long journey is that one can never give up since success may come soon or take a long time. It is important to find a way to be motivated and have enough energy to face the new challenges every day,” he wrote.

The research was eventually published in the Public Library of Science Biology. In the future, the discovery of a new kinase and signaling pathway that senses protein misfolding in the cytoplasm and regulates translation might have important implications for many cellular processes and human diseases.

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