Plasmodium falciparum UvrD activities are downregulated by DNA-interacting compounds and its dsRNA inhibits malaria parasite growth

Abstract

BackgroundHuman malaria parasite infection and its control is a global challenge which is responsible for ~0.65 million deaths every year globally. The emergence of drug resistant malaria parasite is another challenge to fight with malaria. Enormous efforts are being made to identify suitable drug targets in order to develop newer classes of drug. Helicases play crucial roles in DNA metabolism and have been proposed as therapeutic targets for cancer therapy as well as viral and parasitic infections. Genome wide analysis revealed that Plasmodium falciparum possesses UvrD helicase, which is absent in the human host.ResultsRecently the biochemical characterization of P. falciparum UvrD helicase revealed that N-terminal UvrD (PfUDN) hydrolyses ATP, translocates in 3’ to 5’ direction and interacts with MLH to modulate each other’s activity. In this follow up study, further characterization of P. falciparum UvrD helicase is presented. Here, we screened the effect of various DNA interacting compounds on the ATPase and helicase activity of PfUDN. This study resulted into the identification of daunorubicin (daunomycin), netropsin, nogalamycin, and ethidium bromide as the potential inhibitor molecules for the biochemical activities of PfUDN with IC50 values ranging from ~3.0 to ~5.0 μM. Interestingly etoposide did not inhibit the ATPase activity but considerable inhibition of unwinding activity was observed at 20 μM. Further study for analyzing the importance of PfUvrD enzyme in parasite growth revealed that PfUvrD is crucial/important for its growth ex-vivo.ConclusionsAs PfUvrD is absent in human hence on the basis of this study we propose PfUvrD as suitable drug target to control malaria. Some of the PfUvrD inhibitors identified in the present study can be utilized to further design novel and specific inhibitor molecules.

Characterization of Plasmodium falciparum ATP-dependent DNA helicase RuvB3

“…All the effective inhibitors bind strongly to DNA [39], and so they most likely interfere with PfRuvB3 unwinding function, whose domain ought to be distant from that of ATPase. PfRuvB3 is more sensitive to daunorubicin (IC 50 of 0.76 μM) than other helicases, such as P. falciparum DNA helicase A (PfDH A) [22], P. falciparum UvrD helicase (PfUDN) [40], P. falciparum 45 kDa helicase (PfH45) [41], P. falciparum 60 kDa DNA helicase (PfDH60) [42] and human DNA helicase (HDH II) [43] (IC 50s of 2.0, 4.4, 5.0 3.0, 6.23 μM, respectively). However, it is less sensitive to netropsin (IC 50 of 7.09 μM) than PfUDN, PfH45, PfDH60 and P. falciparum Dbp5/DDX19 homolog (PfD66) [44] (IC 50s of 3.3, 0.8, 0.5, 3.2 μM, respectively).…”

Unraveling the importance of the malaria parasite helicases

“…Other studies have reported that helicases are plausible drug targets for malaria control . Using dsRNA‐based approaches, previous studies have shown that some helicases are crucial for the growth and survival of the malaria parasite . Furthermore, recent report suggests that the helicases most likely function in stress survival in P. falciparum .…”

“…PfUvrD is particularly expressed in the schizont stages of the intraerythrocytic development of P. falciparum 3D7 strain and it is restricted to the nucleus only . PfUvrD‐specific dsRNA inhibited the intraerythrocytic development of P. falciparum 3D7 strain suggesting that UvrD is crucial for the development of the parasite . It will be useful to identify the specific inhibitors of PfUvrD because it is parasite‐specific and required for parasite growth.…”

Challenges of drug-resistant malaria

“…In a recent study, P. falciparum UvrD helicase revealed that N-terminal UvrD (PfUDN) dsRNA shows inhibition in the growth of the parasite particularly during earlier phase of schizont development. The study reveals that the growth of parasite was inhibited by approximately 40% by adding PfUDN dsRNA in culture [ 114 ]. Another study observed transcriptional down-regulation of the hypusinated form of either eIF-5A or DHS upon transfection of P. berghei ANKA merozoites with eIF-5A-shRNA and DHS-shRNA, respectively, as hypusination of eIF-5A is important for cell proliferation of the parasite.…”