Scientists find new phosphatase inhibitor with higher selectivity and lower polarity

Phosphatase is a regulatory protein which is as important as kinase, and its function is opposite to kinase, so it can be seen as an endogenous kinase inhibitor. The main obstacle of the development of phosphatase inhibitors is selectivity and through-membrane. Phosphatase substrate is a phosphorylated protein, and its activity pocket is mainly bond to phosphate, so high-polarity reactive ligand is very great and the selectivity is very poor. While when the polarity is too great, it can't reach the target location through the cell membrane. Poor selectivity is difficult to be used to accurately study the biological function of phosphatase. The most famous phosphatase is undoubtedly the target for diabetes PTP1B. There are also many phosphatase recombinant proteins in the market.

Many kinases and phosphatases themselves are in an inactive state (usually the combination of regulatory domain and catalytic domain of protein molecules prevents the combination of substrate and catalytic domain), and they require a certain signal to change conformation to be activated. Clotting proteins in an inactive state, namely the protein glue reported by the media, is not a new concept. The first kinase inhibitor drugs Geli Wei which is a non-active conformation combination with ABL. Recombinant proteins such as recombinant horse proteins are used in the development stage. But for phosphatase, it is indeed the first one.

Their screening method is very interesting. The researchers used a peptide known to activate SHP2 to activate half of the SHP2 and left half of the enzyme which was not activated in order to maintain a dynamic equilibrium which was easily broken and to increase the chances of finding a weak lead compound. Then the researchers used the whole protein and catalytic domain to respectively screen a relatively small compound library, so they can only select the allosteric inhibitor. If the compound inhibits the catalytic domain and the entire protein fragment at the same time, then it showed it conducts inhibition by binding with active pocket. The researchers found a sign compound of 12uM, and they found this lead compound with in-vivo activity through a simple optimization. By expressing SHP2 which lost allosteric binding ability but still had catalytic function, researchers showed convincingly that this compound indeed played the role through SHP2. The crystal structure also proved binding mechanism.

The highlights of this work is filtering mode. They only screened 100,000 compounds to find a good lead compound. The activity of lead compound may be not outstanding, but its through-membrane and selectivity is much better than the previous phosphatase inhibitors. If the other phosphatases are also screened in this way of hundreds of millions of DNA encoded chemical libraries, they should find a lot of similar nature phosphatase inhibitors. If the phosphatase inhibitors with high activity, high selectivity and through-membrane can be easier to be found, phosphatases might become the next popular target. Flarebio provides recombinant proteins such as recombinant Nrg2 with good quality.