Inhibition by stabilization: targeting the Plasmodium falciparum aldolase–TRAP complex

Abstract

BackgroundEmerging resistance of the malaria parasite Plasmodium to current therapies underscores the critical importance of exploring novel strategies for disease eradication. Plasmodium species are obligate intracellular protozoan parasites. They rely on an unusual form of substrate-dependent motility for their migration on and across host-cell membranes and for host cell invasion. This peculiar motility mechanism is driven by the ‘glideosome’, an actin–myosin associated, macromolecular complex anchored to the inner membrane complex of the parasite. Myosin A, actin, aldolase, and thrombospondin-related anonymous protein (TRAP) constitute the molecular core of the glideosome in the sporozoite, the mosquito stage that brings the infection into mammals.MethodsVirtual library screening of a large compound library against the PfAldolase–TRAP complex was used to identify candidate compounds that stabilize and prevent the disassembly of the glideosome. The mechanism of these compounds was confirmed by biochemical, biophysical and parasitological methods.ResultsA novel inhibitory effect on the parasite was achieved by stabilizing a protein–protein interaction within the glideosome components. Compound 24 disrupts the gliding and invasive capabilities of Plasmodium parasites in in vitro parasite assays. A high-resolution, ternary X-ray crystal structure of PfAldolase–TRAP in complex with compound 24 confirms the mode of interaction and serves as a platform for future ligand optimization.ConclusionThis proof-of-concept study presents a novel approach to anti-malarial drug discovery and design. By strengthening a protein–protein interaction within the parasite, an avenue towards inhibiting a previously “undruggable” target is revealed and the motility motor responsible for successful invasion of host cells is rendered inactive. This study provides new insights into the malaria parasite cell invasion machinery and convincingly demonstrates that liver cell invasion is dramatically reduced by 95 % in the presence of the small molecule stabilizer compound 24.Electronic supplementary materialThe online version of this article (doi:10.1186/s12936-015-0834-9) contains supplementary material, which is available to authorized users.

Multiplexed quantitative proteomics provides mechanistic cues for malaria severity and complexity

“…Enolase along with HSP 70 and iron superoxide dismutase forms the DegP complex which protects the parasite from heat and oxidative stress in the host system 35 . FBA and actin have been reported to interact with TRAP and TRAP like protein (TLP) for sporozoites gliding and invasion 36 . SERA4, along with the other SERA member proteins, helps in maintaining the blood stage of the pathogen's life cycle.…”

A Putative Small Solute Transporter Is Responsible for the Secretion of G377 and TRAP-Containing Secretory Vesicles during Plasmodium Gamete Egress and Sporozoite Motility

“…Blood of infected mice was harvested and gametocytes purified using a 49% Nycodenz cushion at 37°C (1500rpm; 20min). Cells were washed with PBS and transferred to ookinete medium (250ml RPMI, 12.5mg Hypoxanthine, 2.5ml Pen/Strep, 0.5g NaHCO3, 5.12mg xanthurenic) at 19°C [ 21 ]. After indicated time points cells were either fixed with 4% PFA in PBS for immunostaining, or lysed in RIPA buffer for Western blot analyses.…”

“…Sporozoites are a key model to understanding this unique type of motility, which can be studied in vitro or in vivo . The mechanisms underlying gliding motility are not completely understood [ 17 – 21 ]. However various TRAP family proteins (S6, TLP, TRAP) appear to play distinct roles during sporozoite adhesion and motility [ 22 – 25 ].…”

Stabilization of protein-protein interactions in drug discovery

“…In 2015, the group of Bosch published a molecule (Compound 24) that stabilizes the complex between an aldolase from Plasmodium palcifarum (PfAldolase) and thrombospondinrelated anonymous protein (TRAP) [151]. The malaria-causing protozoan parasite Plasmodium palcifarum uses an actin/myosin motor complex located beneath the parasite's plasma membrane for cellular invasion and gliding [152].…”