title: Assessing subunit dependency of the Plasmodium proteasome using small molecule inhibitors and active site probes.
abstract: The ubiquitin-proteasome system (UPS) is a potential pathway for therapeutic intervention for pathogens such as Plasmodium, the causative agent of malaria. However, due to the essential nature of this proteolytic pathway, proteasome inhibitors must avoid inhibition of the host enzyme complex to prevent toxic side effects. The Plasmodium proteasome is poorly characterized, making rational design of inhibitors that induce selective parasite killing difficult. In this study, we developed a chemical probe that labels all catalytic sites of the Plasmodium proteasome. Using this probe, we identified several subunit selective small molecule inhibitors of the parasite enzyme complex. Treatment with an inhibitor that is specific for the β5 subunit during blood stage schizogony led to a dramatic decrease in parasite replication while short-term inhibition of the β2 subunit did not affect viability. Interestingly, coinhibition of both the β2 and β5 catalytic subunits resulted in enhanced parasite killing at all stages of the blood stage life cycle and reduced parasite levels in vivo to barely detectable levels. Parasite killing was achieved with overall low host toxicity, something that has not been possible with existing proteasome inhibitors. Our results highlight differences in the subunit dependency of the parasite and human proteasome, thus providing a strategy for development of potent antimalarial drugs with overall low host toxicity.
authors.affiliation: Department of Chemical and Systems Biology and ‡Department of Pathology, Stanford University School of Medicine , 300 Pasteur Drive, Stanford, California 94305-5324, United States.
authors.forename: Hao
authors.initials: H
authors.lastname: Li
authors.forename: Wouter A
authors.initials: WA
authors.lastname: van der Linden
authors.forename: Martijn
authors.initials: M
authors.lastname: Verdoes
authors.forename: Bogdan I
authors.initials: BI
authors.lastname: Florea
authors.forename: Fiona E
authors.initials: FE
authors.lastname: McAllister
authors.forename: Kavitha
authors.initials: K
authors.lastname: Govindaswamy
authors.forename: Joshua E
authors.initials: JE
authors.lastname: Elias
authors.forename: Purnima
authors.initials: P
authors.lastname: Bhanot
authors.forename: Herman S
authors.initials: HS
authors.lastname: Overkleeft
authors.forename: Matthew
authors.initials: M
authors.lastname: Bogyo
mesh_terms: D020134:Catalytic Domain; D015335:Molecular Probes; D010961:Plasmodium / Q000201:enzymology* / Q000254:growth & development; D011480:Protease Inhibitors / Q000494:pharmacology*; D046988:Proteasome Endopeptidase Complex / Q000187:drug effects / Q000378:metabolism*
chemical_list: D015335:Molecular Probes; D011480:Protease Inhibitors; D046988:Proteasome Endopeptidase Complex