Disruption of a mitochondrial protease machinery in Plasmodium falciparum is an intrinsic signal for parasite cell death

Abstract

The ATP-dependent ClpQY protease system in Plasmodium falciparum is a prokaryotic machinery in the parasite. In the present study, we have identified the complete ClpQY system in P. falciparum and elucidated its functional importance in survival and growth of asexual stage parasites. We characterized the interaction of P. falciparum ClpQ protease (PfClpQ) and PfClpY ATPase components, and showed that a short stretch of residues at the C terminus of PfClpY has an important role in this interaction; a synthetic peptide corresponding to this region antagonizes this interaction and interferes with the functioning of this machinery in the parasite. Disruption of ClpQY function by this peptide caused hindrance in the parasite growth and maturation of asexual stages of parasites. Detailed analyses of cellular effects in these parasites showed features of apoptosis-like cell death. The peptide-treated parasites showed mitochondrial dysfunction and loss of mitochondrial membrane potential. Dysfunctioning of mitochondria initiated a cascade of reactions in parasites, including activation of VAD–FMK-binding proteases and nucleases, which resulted in apoptosis-like cell death. These results show functional importance of mitochondrial proteases in the parasite and involvement of mitochondria in programmed cell death in the malaria parasites.

Protein Degradation Systems as Antimalarial Therapeutic Targets

“…In addition to the eukaryotic proteasome, Plasmodium homologs of the catalytic subunit of the prokaryotic proteasome caseinolytic protease Q (ClpQ), also known as heat shock locus V (HslV), and its regulatory chaperone ClpY/HslU have been identified in P. falciparum (PfClpQ, PF3D7_1230400, and PfClpY, PF3D7_0907400) [84, 85]. PfClpY and PfClpQ proteins are expressed at the trophozoite, schizont, and merozoite stages [84–86].…”

Cell death offers exceptional cellular and molecular windows for pharmacological interventions in protozoan parasites

“…Unicellular eukaryotes possess several factors from both host and vector could participate to apoptosis-like death, including Anopheles NOS, mammalian NOS II, Ca 2+ and NOS-independent factors, such as ROS and TGF-b1 [62,63]. Mitochondrial protease machinery in Plasmodium falciparum has been associated with apoptosis-like cell death [64]. The upstream regulators, caspase-like proteases, the metacaspases (MCA), are considered to exert the caspase function in protozoan parasites, plant and fungi.…”

The influence of ATP-dependent proteases on a variety of nucleoid-associated processes

“…The HslUV protease has only been positively identified in eubacteria to date, though genome sequences suggest that an archaeal homolog should also exist (Aksam et al, 2007;Chen et al, 2008;Cheng et al, 2008;Matsushima and Kaguni, 2011;Sinvany-Villalobo et al, 2004;Tatsuta and Langer, 2009). The AAA+ proteases can also be found in specific organelles of unicellular parasites: in the apicoplast of Plasmodium falciparum (El Bakkouri et al, 2010;Rathore et al, 2010Rathore et al, , 2011 and the kinetoplast of Trypanosoma brucei , for example. These organisms are the only eukaryotes known which possess an HslUV homolog; it is found in the kinetoplast (El Bakkouri et al, 2010;Rathore et al, 2010Rathore et al, , 2011.…”

“…The AAA+ proteases can also be found in specific organelles of unicellular parasites: in the apicoplast of Plasmodium falciparum (El Bakkouri et al, 2010;Rathore et al, 2010Rathore et al, , 2011 and the kinetoplast of Trypanosoma brucei , for example. These organisms are the only eukaryotes known which possess an HslUV homolog; it is found in the kinetoplast (El Bakkouri et al, 2010;Rathore et al, 2010Rathore et al, , 2011. Almost all ATP-dependent proteases functioning in eukaryotic organelles are encoded by the nuclear genome and are transported into appropriate organelles based on targeting signal sequences.…”

“…U1 b-lactone had no observable effect on the morphology and segregation of mitochondria when another ATP-dependent protease, an analogue of HslUV (PfClpQY), was still functional. Inhibition of PfClpQY activity by a specific peptide which disrupts protease complex formation causes loss of mitochondrial membrane potential, impairment of mitochondrial growth and function and leads to apoptotic-like cell death of the parasite (Rathore et al, 2011). In another parasite, Trypanosoma brucei, depletion of TbHslUV leads to an increase in the number of kinetoplasts (dense granules of circular DNA within the parasite's large mitochondrion) which undergo abnormal segregation, causing the appearance of giant kinetoplasts as a result of the overreplication of minicircle DNA .…”