Mechanistic Basis for Therapeutic Targeting of the Mitochondrial F1Fo-ATPase

Abstract

Altered cellular bioenergetics are implicated in many disease processes, and modulating the F 1 F o -ATPase, the enzyme responsible for producing the majority of ATP in eukaryotic cells, has been proposed to have therapeutic utility. Bz-423 is a 1,4-benzodiazepine that binds to the oligomycin sensitivity-conferring protein subunit of the mitochondrial F 1 F o -ATPase and inhibits the enzyme. In response to Bz-423, cells moderately decrease ATP synthesis and significantly increase superoxide, resulting in redox-regulated apoptosis. Administering Bz-423 to autoimmune mice leads to apoptosis of pathogenic cells and potent attenuation of disease progression. To determine if a mechanism of action distinguishes Bz-423 from toxic F 1 F o -ATPase inhibitors like oligomycin, we studied how both compounds inhibit the enzyme. Oligomycin is a high-affinity mixed inhibitor, displaying time-dependent inhibition, resulting in severe depletion of ATP. In contrast, Bz-423 is an allosteric inhibitor with lower affinity that rapidly dissociates from the enzyme. Our data support a model in which the interplay of these features underlies the favorable properties of Bz-423. They also represent key criteria for the development of therapeutic F 1 F o -ATPase inhibitors, which should have utility across a range of areas.