Identification of Human UMP/CMP Kinase 1 as Doxorubicin Binding Target Using Protein Microarray

Area of Science:

• Biochemistry
• Molecular Biology
• Pharmacology

Background:

• Doxorubicin (DOX) is a crucial anthracycline chemotherapy agent.
• The molecular mechanisms underlying DOX's side effects, including cardiotoxicity, apoptosis, and drug resistance, remain largely uncharacterized.
• Understanding DOX's off-target interactions is vital for mitigating adverse effects.

Purpose of the Study:

• To identify novel molecular targets of Doxorubicin (DOX) in human cells.
• To elucidate the binding interaction between DOX and its identified targets.
• To investigate the functional consequences of DOX binding to its targets.

Main Methods:

• High-throughput screening of 17,950 human proteins expressed in HEK293 cells to identify DOX-binding proteins.
• Competitive and binding assays to confirm DOX-CMPK1 interaction.
• Microscale thermophoresis to quantify the binding affinity (K_d) of DOX to CMPK1.
• Enzyme activity assays to assess the effect of DOX on CMPK1 phosphorylation.

Main Results:

• Fourteen human proteins were identified as potential DOX binders, with UMP/CMP kinase 1 (CMPK1) being a key hit.
• Doxorubicin (DOX) binds to CMPK1 with a dissociation constant (K_d) of 1216 nM.
• DOX binding activates CMPK1-mediated phosphorylation of CMP, dCMP, and UMP in a dose-dependent manner.
• DOX modulates CMPK1 activity, enhancing stimulation by DTT and overcoming inhibition by NaF and EDTA, suggesting interaction at a non-active site involving magnesium.

Conclusions:

• Doxorubicin (DOX) directly binds to UMP/CMP kinase 1 (CMPK1).
• DOX binding to CMPK1 activates its enzymatic activity, potentially contributing to DOX's known side effects and resistance mechanisms.
• The findings suggest a novel mechanism for DOX's action and highlight CMPK1 as a potential target for therapeutic intervention.