Compound Reveals New Link Between Signaling Protein And Cell Migration

The protein, known as Raf Kinase Inhibitor Protein, or RKIP, controlsactivity of kinases, a type of enzyme that acts as a key component inthe biochemical signaling pathways responsible for determining almostall cellular activity. But RKIP's own activity is inhibited when asmall molecule organic compound called locostatin, discovered earlierby UIC researchers, binds to it.

Lead investigator Gabriel Fenteany, assistant professor of chemistry atUIC, reports the finding in the Sept. 26 issue of the journal Chemistryand Biology.

The researchers used an approach sometimes called "forward chemicalgenetics" whereby they first identified locostatin as an inhibitor ofcell migration, then used locostatin itself as a kind of bait to fishout the protein to which it binds. That protein was RKIP.

"We have implicated this protein in controlling cell migration,a role it was not previously known to play," said Fenteany. "It's amolecular target of locostatin. We found this on the basis of thechemical affinity of locostatin for this protein."

As a regulatory protein, RKIP controls the functions of kinases,thereby governing signaling pathways. When these pathways are notproperly controlled, all kinds of diseases can result, including cancer.

Fenteany and his team also confirmed that RKIP is involved in cell migration by using other methods.

"After finding that locostatin targets RKIP, we wanted to verify thatRKIP really does control cell migration," Fenteany said. Theresearchers removed, or knocked down, RKIP in the cell using a methodcalled RNA interference and looked at the effect on cell migration.They did the opposite manipulation as well -- artificially increasingthe amount of RKIP in the cell and again looking at the effect on cellmigration. In each case, the result was consistent with RKIP having animportant, positive role in the control of cell migration.

"The interest in RKIP now is that it is a new and apparently importantmodulator of cell migration and therefore a possible target inanti-cancer strategies focused on limiting tumor angiogenesis andmetastasis," Fenteany said.

More investigation on how exactly RKIP controls cell migration isneeded, Fenteany said. UIC researchers are also trying to determine thepotential of locostatin as a drug by looking at its effects ondifferent types of cells and tissues.

Fenteany's team included UIC chemistry graduate students Shoutian Zhuand Kevin Mc Henry. Zhu purified the RKIP, analyzed the effect oflocostatin on its activity and performed different experiments to lowerand raise the level of RKIP in cells. Mc Henry performed most of thecell migration assays. Additional chemical analysis was performed byWilliam Lane of the Harvard Microchemistry and Proteomics AnalysisFacility.

Funding for the research was provided by the National Cancer Instituteof the National Institutes of Health, and the American Cancer Society.