Researchers have found a way to manipulate a cell’s cilia, a finding that could lead to advances in scientists’ ability to understand and eventually repair them. The research was done in mouse cells by scientists at Johns Hopkins Medicine and the National Tsing Hua University in Taiwan and published in Nature Communications.
Malfunctioning of human cilia can cause a range of human diseases such as polycystic kidney disease, an incurable condition in which fluid-filled cysts interfere with kidney function. Being able to better understand cilia would allow researchers to search for cures to these diseases but the structures have been difficult to study due to cilia’s small size—10,000 times smaller than a cell—rendering traditional cell analysis tools unusable.
To solve this issue, the researchers used a tool called chemically inducible dimerization, which is able to mesh two specific chemicals together at specific sites within a living cell, to manipulate a chemical signaling pathway within cilia that controls how molecules are shuttled up and down the length of the structure.
The team added two proteins to cells from mice grown in the lab. The first, called FRB, is capable of glomming onto microtubules within cilia. The second, FKBP, attaches to an enzyme that acts as an erasure for glutamylation in cilia. FKBP and the enzyme float around into the cell until rapamycin is added, at which point FKBP gets trapped at the FRB molecules within the cilia. The enzyme can effectively erase the glutamylation modification once it is inside the cilia.
When glutamylation in cilia is rapidly removed, molecules flow more slowly toward the tip, allowing scientists to track cilia activity. The scientists named their molecule matchmaking STRIP for spatiotemporal rewriting intraciliary post-translational modifications.
"Our STRIP system offers a new strategy for precisely controlling microtubule modifications in living cells. With this approach, it becomes possible to understand how microtubules regulate cellular functions and may also serve as a new way to treat human diseases in the future," says Yu-Chun Lin, Ph.D., an assistant professor at the Institute of Molecular Medicine at the National Tsing Hua University in Taiwan.
The scientists plan to apply STRIP to human cells and look more closely at glutamylation in cilia, as well as control other chemical modifications in cilia.
Image: These are primary cilia in a mouse embryonic node. Image courtesy of Shinohara Kyosuke, Tokyo University of Agriculture and Technology.