The binding of C-terminal targeted drugs to Hsp90α/β complexes
Weiya Liu, Megan Swink, and George A Vielhauer*
The University of Kansas Cancer Center, 3901 Rainbow BLVD, Kansas City, KS, 66160
KU174 , a C-terminal Hsp90 inhibitor, exhibit robust anti-proliferative and cytotoxic activity along with client protein degradation and disruption of Hsp90 native complexes without induction of the heat shock response (HSR). Furthermore, KU174 demonstrates direct binding to the Hsp90 protein in cancer cells. By using the fluorescence signal from the drug and Hsp90 protein, we are able to develop the FL assay to study the binding of KU174 to the recombinant Hsp90 α and β. The experiment results show that, the Kd for Hsp90α is 19.85 μM , while the Kd for Hsp90β is 37.38 μM. Both Hsp90α and β can enhance the KU174’s fluorescence peak intensity upon binding, but HSP90α can cause larger increase. HSC70, on the contrary, only decreases KU174’s fluorescence peak intensity. Further studies also show that, pre-incubate the Hsp90 with 17AAG, a N-terminal targeted drug, may cause a slow time-dependent conformation change in the protein , which makes the influence on KU174 quite different from that of native Hsp90 α and β.