Perturbation of copper homeostasis is instrumental in early developmental arrest of intraerythrocytic Plasmodium falciparum

Abstract

BackgroundMalaria continues to be a devastating disease. The elucidation of factors inducing asexual growth versus arrest of Plasmodium falciparum can provide information about the development of the parasite, and may help in the search for novel malaria medication. Based on information from genome-wide transcriptome profiling of different developmental stages of P. falciparum, we investigated the critical importance of copper homeostasis in the developmental succession of P. falciparum with regard to three aspects of copper function. These were:1) inhibition of copper-binding proteins, 2) copper-ion chelation, and 3) down-regulated expression of genes encoding copper-binding proteins associated with a specific growth-promoting factor.ResultsInhibition of copper-binding proteins with tetrathiomolybdate (TTM) caused cessation of growth of the parasite. TTM arrested the parasite irreversibly during the trophozoite to schizont stage progression. Target molecules for TTM may be present in P. falciparum. The involvement of copper ions in developmental arrest was also investigated by copper-ion chelating methods, which indicated a critical function of reduced copper ions (Cu1+) in the parasite during the early developmental stage. Copper ions, not only in the parasite but also in host cells, were targets of the chelators. Chelation of Cu1+caused blockage of trophozoite progression from the ring stage. Profound growth arrest was detected in parasites cultured in a chemically defined medium containing hexadecanoic acid alone as a growth-promoting factor. This developmental arrest was associated with down-regulated expression of genes encoding copper-binding proteins. Cis-9-octadecenoic acid completely prevented the down-regulation of gene expression and developmental arrest that were observed with the use of hexadecanoic acid.ConclusionsThe critical importance of copper homeostasis in early developmental stages of P. falciparum was confirmed. Perturbation of copper homeostasis induced profound and early developmental arrest of P. falciparum. These findings should help to elucidate the mechanisms behind the development of P. falciparum, and may be applied in the development of effective antimalarial strategies.

The Yin and Yang of copper during infection

“…One size will not fit all pathogens when it comes to copper and depending on the site and course of infection, the invading microbe may be subject to either toxic copper overload or deprivation of this essential nutrient. It is important to note that the examples of copper limitation provided here are with fungal pathogens, yet eukaryotic parasitic microbes may also be vulnerable to copper limitation inside the host, as has been reported for Plasmodium falciparum [87]. Lastly, it is important to remember that although bacterial cells are classically known for their copper avoidance behavior, they still require this metal to activate cuproenzymes in the periplasmic or extracellular environment such as COX for respiration, Cu/Zn SOD to remove superoxide free radicals and multi-copper oxidases for copper detoxification [25, 60, 61].…”

Copper Homeostasis for the Developmental Progression of Intraerythrocytic Malarial Parasite

“…Experimental findings show: i) selective removal of Cu + with 2,9-dimethyl-1,10-phenanthroline, hydrochloride (neocuproine, C 14 H 12 N 4 ) has inhibited completely the developmental stages of P. falciparum in RBCs (ring forms, trophozoites and schizonts) [ 16 , 17 , 71 ]; ii) a tetrathiomolybdate, which is a specific inhibitor of copper-binding proteins that regulate copper physiology and function by actively associating with copper ions, has arrested development of the parasite [ 17 ]; and iii) a specific growth-promoting factor (C16:0) has arrested early development of the parasite in association with profoundly down-regulated expression of genes encoding copper-binding proteins [ 7 , 15 , 17 ]. These findings suggest the optimal copper homeostasis is critical for the intraerythrocytic developmental succession of P. falciparum .…”

“…These results indicate that the target molecules for TTM that are involved in the developmental arrest of P. falciparum can occur predominantly in the parasite, but not in host RBCs. Further TTM has reacted irreversibly with the copper-binding proteins of the parasite [ 17 ].…”

“…One of the 5 transcripts has been a putative copper channel. In addition, selective removal of copper ions has inhibited completely the successive ring–trophozoite–schizont progression of the parasite [ 16 , 17 ]. Inhibition of copper-binding proteins that control copper function by actively associating with copper ions has caused arrested development of P. falciparum , implying the importance of copper homeostasis for the developmental progression of P. falciparum .…”

“…Inhibition of copper-binding proteins that control copper function by actively associating with copper ions has caused arrested development of P. falciparum , implying the importance of copper homeostasis for the developmental progression of P. falciparum . Reduced expression of genes encoding copper-binding proteins has been detected, in association with arrested development of the parasite cultured in the medium enriched with specific growth-promoting NEFAs, including hexadecanoic acid (palmitic acid, C16:0) and trans -9-octadecenoic acid (C18:1- trans -9) [ 16 , 17 ]. These data have provided intense evidence for a link between healthy copper homeostasis and developmental progression of P. falciparum , and may be useful for drug and vaccine development for the malaria eradication.…”