GRP78/BiP/HSPA5/Dna K is a universal therapeutic target for human disease.
Bottom Line: The GRP78 inhibitor OSU-03012 (AR-12) interacted with sildenafil (Viagra) or tadalafil (Cialis) to rapidly reduce GRP78 levels in eukaryotes and as a single agent reduce Dna K levels in prokaryotes.Pre-treatment with OSU-03012/sildenafil reduced expression of the coxsakie and adenovirus receptor in parallel with it also reducing the ability of a serotype 5 adenovirus or coxsakie virus B4 to infect and to reproduce.OSU-03012 as a single agent at clinically relevant concentrations killed laboratory generated antibiotic resistant E. coli and clinical isolate multi-drug resistant N. gonorrhoeae and MRSE which was in bacteria associated with reduced Dna K and Rec A expression.
Affiliation: Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, VA 23298.Show MeSH
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Mentions: Bacteria express a homologue of GRP78, Dna K. Treatment of antibiotic sensitive wild type E. coli bacteria with OSU-03012 significantly reduced proliferation and enhanced penicillin/streptomycin toxicity (Fig. 7A). Treatment of laboratory generated ampacillin and kayamycin resistant E. coli bacteria with OSU-03012 significantly reduced proliferation (Fig. 7B). We know that OSU-03012 reduces the half-life of mammalian GRP78 and in the present studies we discovered that OSU-03012 could down-regulate DNA K expression (Fig. 7C). Bacteria also contain di-cyclic GMP phosphodiesterases that limit intracellular concentrations of cyclic nucleotides which when highly elevated are toxic (Tuckerman et al., 2011). Thus of particular note was that antibiotic resistant E. coli were also killed by the PDE5 inhibitors sildenafil (Viagra) or tadalafil (Cialis). In dose-response studies OSU-03012, sildenafil or tadalafil profoundly suppressed bacterial growth at very low clinically relevant concentrations (Fig. 7D). The decline in Dna K expression correlated with reduced expression of a Dna K chaperoned protein, Rec A. In the case of the chaperones GrpE (HSP27) and DNA J (HSP40), treatment with either sildenafil, tadalafil or OSU-03012 caused the appearance of a slower migrating species of the protein on SDS PAGE, that in mammalian cells would be linked to increased protein phosphorylation (Fig. 7C). These findings with OSU-03012 also correlated with significant morphological changes in the coliform bacteria, with surviving Gram-stained E. coli cells treated with OSU-03012 (2 μM) for 3 h appearing either elongated or “fat” in appearance (Fig. 7C).
Affiliation: Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, VA 23298.