Inhibition of ATP synthase by chlorinated adenosine analogue

Abstract

8-Chloroadenosine (8-Cl-Ado) is a ribonucleoside analogue that is currently in clinical trial for chronic lymphocytic leukemia. Based on the decline in cellular ATP pool following 8-Cl-Ado treatment, we hypothesized that 8-Cl-ADP and 8-Cl-ATP may interfere with ATP synthase, a key enzyme in ATP production. Mitochondrial ATP synthase is composed of two major parts; FO intermembrane base and F1 domain, containing α and β subunits. Crystal structures of both α and β subunits that bind to the substrate, ADP, are known in tight binding (αdpβdp) and loose binding (αtpβtp) states. Molecular docking demonstrated that 8-Cl-ADP/8-Cl-ATP occupied similar binding modes as ADP/ATP in the tight and loose binding sites of ATP synthase, respectively, suggesting that the chlorinated nucleotide metabolites may be functional substrates and inhibitors of the enzyme. The computational predictions were consistent with our whole cell biochemical results. Oligomycin, an established pharmacological inhibitor of ATP synthase, decreased both ATP and 8-Cl-ATP formation from exogenous substrates, however, did not affect pyrimidine nucleoside analogue triphosphate accumulation. Synthesis of ATP from ADP was inhibited in cells loaded with 8-Cl-ATP. These biochemical studies are in consent with the computational modeling; in the αtpβtp state 8-Cl-ATP occupies similar binding as ANP, a non-hydrolyzable ATP mimic that is a known inhibitor. Similarly, in the substrate binding site (αdpβdp) 8-Cl-ATP occupies a similar position as ATP mimic ADP-BeF3 −. Collectively, our current work suggests that 8-Cl-ADP may serve as a substrate and the 8-Cl-ATP may be an inhibitor of ATP synthase.

8-Amino-Adenosine Inhibits Multiple Mechanisms of Transcription

“…Another congener, 8-chloro-adenosine, causes an ATP pool decline as well as an inhibition of RNA synthesis (11, 13, 29–32). The precise mechanism by which 8-amino-adenosine causes a decline in the ATP pool has not been determined although it is feasible that, similar to the chlorinated adenosine analog, 8-amino-ADP is a substrate for ATP synthase and/or 8-amino-ATP may act as an inhibitor of the ATP synthase (33). …”

ATP Analog Enhances the Actions of a Heat Shock Protein 90 Inhibitor in Multiple Myeloma Cells

“…The accumulation of the cytotoxic metabolite results in a parallel decrease of the ATP cellular pools (Gandhi et al, 2001;Chen et al, 2009). 8-ClAdo gets incorporated into RNA during transcription, hindering this process (Stellrecht et al, 2003).…”

“…8-Cl-Ado can inhibit transcription and translation processes because of its actions not only on RNA incorporation and termination but also on the decrease of endogenous ATP pool levels (Gandhi et al, 2001;Stellrecht et al, 2003;Chen et al, 2009). The combination of both agents resulted in a drastic decrease (Ͼ75%) in STAT3, Raf-1, and Akt compared with that in untreated controls as well as the single agents in MM.1S and U226 cells; this decrease was minimal in the RPMI-8226 cell line (Fig.…”

Liquid chromatographic methods for the determination of endogenous nucleotides and nucleotide analogs used in cancer therapy: A review

“…Another, less studied nucleoside analog, 8-chloroadenosine (8-Cl-Ado) was recently shown to exert its activity through inhibition of ATP synthase [25]. This results in decreased ATP concentrations in 8-Cl-Ado treated cells.…”