Radioprotective thiolamines WR-1065 and WR-33278 selectively denature nonhistone nuclear proteins

Area of Science:

• Biochemistry
• Cell Biology
• Radioprotection

Background:

• Radioprotective agents like WR-1065 are crucial in radiation therapy.
• Understanding their interaction with cellular components is vital for optimizing their use.
• Nuclear proteins play critical roles in DNA stability and cellular function.

Purpose of the Study:

• To investigate the interactions between the radioprotector WR-1065 and nuclear components.
• To determine the effect of WR-1065 on the thermal stability and denaturation of nuclear proteins.
• To elucidate the mechanism of WR-1065-induced nuclear protein denaturation.

Main Methods:

• Differential scanning calorimetry (DSC) was employed to analyze macromolecular denaturation.
• Isolated nuclei from Chinese hamster V79 cells were treated with WR-1065 and other thiol compounds.
• Protein insolubility was quantified to assess denaturation extent in both isolated nuclei and intact cells.

Main Results:

• WR-1065 induced irreversible denaturation of nuclear proteins, including nuclear matrix proteins.
• Significant protein denaturation was observed in isolated nuclei and nuclei of intact V79 cells.
• WR-1065 is expected to contribute to drug toxicity at concentrations above approximately 4 mM.
• The disulfide form WR-33278 was more effective at denaturing nuclear proteins than WR-1065.
• Denaturation likely occurs via interaction with protein cysteine groups, forming destabilizing disulfides.

Conclusions:

• WR-1065 effectively denatures nuclear proteins, a process linked to drug toxicity.
• This denaturation is specific to the nuclear environment, suggesting a role for DNA in concentrating the drug.
• The findings provide insights into the molecular mechanisms of radioprotector action and toxicity.