The chaperone molecule was HSP70, which stands for "heat shock protein 70." It assists with the folding of proteins into their correct three-dimensional shapes, even when cells are under stress from elevated body temperatures, such as a fever.
Grimes said she was a little skeptical at first about pursuing studies with HSP70 because it is a commonly known protein, but she found Mohanan's initial data intriguing.
"Vishnu found that if we increased the expression level of HSP70, the NOD2 Crohn's mutants were able to respond to bacterial cell wall fragments. A hallmark of the NOD2 mutations is inability to respond to these fragments. Essentially, Vishnu found a fix for NOD2, and we wanted to determine how we were fixing it."
In further experiments, Mohanan created a tagged-wild-type NOD2 cell line in which NOD2 levels nearly matched the levels found in nature (versus "super" levels that might stimulate an artificial response) and found that NOD2 became more stabilized and degraded more slowly when treated with HSP70. In fact, HSP70 increased the half-life of NOD2 by more than four hours.
"Basically, HSP70 keeps the protein around it kind of watches over and protects NOD2, and keeps it from going in the cellular trash can," Grimes explains.
The researchers tested three human cell lines in their study: kidney cells, colon cells and white blood cells. In the next phase of the study, patient tissue will be examined through a collaboration with Nemours/A.I. duPont Hospital for Children to determine if NOD2 levels can be controlled via HSP70 expression.
"We want to figure out why the mutation in NOD2 results in an increase in inflammation," says Mohanan. "Right now, we have limited knowledge. Once the signaling mechanism is figured out, we will have the keystone."
Mohanan, who is from the s
|Contact: Donna O'Brien|
University of Delaware