London, April 14 : Tufts University researchers in the US have uncovered three molecules that inhibit the protein RIP1 kinase, which can direct cell death.
Medically, the phenomenon whereby cells die is called necrosis. It may lead to tissue damage, and ultimately contribute to death or long-term disability.
The identification of the molecules that target RIP1 kinase is significant because it may open the door to a novel avenue for drug development, say the researchers.
"Our research found that RIP1 kinase can be inhibited by three small molecules: necrostatin-1, -3 and -5," Nature Chemical Biology quoted Dr. Alexei Degterev, assistant professor at Tufts University School of Medicine and member of the biochemistry program faculty of the Sackler School of Graduate Biomedical Sciences, as saying.
"Overall, these data establish RIP1 kinase as a new target for therapeutic drug development for human diseases involving necrotic tissue injury, and they establish necrostatins as first-in-class potent and selective inhibitors of RIP1 kinase," write the authors of the study.
The researchers say that necrosis is relevant to many diseases, especially ones that involve an acute event like heart attack or stroke.
"Cells are programmed to die when they reach the end of their lifecycle and that regulated process is called apoptosis. Cells can also be killed through pathways not controlled by apoptosis. Until recently, this type of cell death, termed necrosis, was believed to be unregulated, a type of accidental cell death caused when cells are placed under extreme stress such as during a heart attack, stroke or organ failure," says Degterev.
Several other studies have shown that necroptosis, a type of necrosis, is regulated by a specific biochemical pathway.
"Through our previous work, we have developed potent and specific small molecules capable of preventing necroptosis in isolated cells," Degterev says while telling about the work .
The work conducted in the laboratory of Dr. Junying Yuan, professor at Harvard Medical School, was subsequently awarded patents.
"The next step, then, was to look for the target of the inhibition by necrostatins to understand how they inhibit necroptosis. We were particularly interested in RIP1 kinase because it was previously reported by other groups to be important for necroptosis and necrostatin-1 looked similar to known kinase inhibitors," say the authors.
With a view to determining the role that necrostatins played in inhibiting necroptosis, the researchers employed several molecular techniques.
In one test, aimed at establishing whether necrostatin-1 is a RIP1 kinase inhibitor, they added it in incremental doses to purified the protein, and observed a dose-dependent decrease in its activity (phosphorylation).
For validating their discovery, the researchers made small and specific structural changes to necrostatin-1, to see if loss of the RIP1 kinase inhibition resulted in the inability of the necrostatin-1 analogs to prevent necrosis.
The researchers got surprised when they saw similar experiments for necrostatin-3 and necrostatin-5 providing similar results, as the structure of the two molecules are very different from that of necrostatin-1.
Based on their observations, the researchers charted the model describing mechanisms of RIP1 inhibition by necrostatin-1.
"Next, research needs to determine the cellular pathway initiated by RIP1 kinase activity, develop better tools to further investigate its role in human disease, and establish how necrostatins are able to prevent RIP1 kinase from signaling the cell to kill itself. This may one day result in effective therapies, currently not available, for many life-threatening diseases," says Degterev.
"These findings on RIP1 kinase inhibitors suggest entirely new possibilities to investigating the role of necroptosis in disease and indicate that these inhibitors may provide ways to prevent extensive tissue damage. Discoveries like this reveal how basic science research provides the foundation to our understanding of disease and can point toward possible novel therapeutic strategies to ease the burden of those diseases," says Dr. Naomi Rosenberg, dean at the Sackler School of Graduate Biomedical Sciences and vice dean for research at Tufts University School of Medicine.