RESUMO
We describe noncovalent, reversible asparagine ethylenediamine (AsnEDA) inhibitors of the Plasmodium falciparum proteasome (Pf20S) ß5 subunit that spare all active subunits of human constitutive and immuno-proteasomes. The compounds are active against erythrocytic, sexual, and liver-stage parasites, against parasites resistant to current antimalarials, and against P. falciparum strains from patients in Africa. The ß5 inhibitors synergize with a ß2 inhibitor in vitro and in mice and with artemisinin. P. falciparum selected for resistance to an AsnEDA ß5 inhibitor surprisingly harbored a point mutation in the noncatalytic ß6 subunit. The ß6 mutant was resistant to the species-selective Pf20S ß5 inhibitor but remained sensitive to the species-nonselective ß5 inhibitors bortezomib and carfilzomib. Moreover, resistance to the Pf20S ß5 inhibitor was accompanied by increased sensitivity to a Pf20S ß2 inhibitor. Finally, the ß5 inhibitor-resistant mutant had a fitness cost that was exacerbated by irradiation. Thus, used in combination, multistage-active inhibitors of the Pf20S ß5 and ß2 subunits afford synergistic antimalarial activity with a potential to delay the emergence of resistance to artemisinins and each other.
Assuntos
Antimaláricos/química , Plasmodium falciparum/enzimologia , Complexo de Endopeptidases do Proteassoma/química , Inibidores de Proteassoma/química , Proteínas de Protozoários/antagonistas & inibidores , Artemisininas/química , Bortezomib/química , Resistência Microbiana a Medicamentos , Humanos , Lactonas/química , Oligopeptídeos/química , Proteínas de Protozoários/químicaRESUMO
Membrane-bound receptors often form large assemblies resulting from binding to soluble ligands, cell-surface molecules on other cells and extracellular matrix proteins. For example, the association of membrane proteins with proteins on different cells (trans-interactions) can drive the oligomerization of proteins on the same cell (cis-interactions). A central problem in understanding the molecular basis of such phenomena is that equilibrium constants are generally measured in three-dimensional solution and are thus difficult to relate to the two-dimensional environment of a membrane surface. Here we present a theoretical treatment that converts three-dimensional affinities to two dimensions, accounting directly for the structure and dynamics of the membrane-bound molecules. Using a multiscale simulation approach, we apply the theory to explain the formation of ordered, junction-like clusters by classical cadherin adhesion proteins. The approach features atomic-scale molecular dynamics simulations to determine interdomain flexibility, Monte Carlo simulations of multidomain motion and lattice simulations of junction formation. A finding of general relevance is that changes in interdomain motion on trans-binding have a crucial role in driving the lateral, cis-, clustering of adhesion receptors.