A novel leishmanial copper P-type ATPase plays a vital role in parasite infection and intracellular survival

Advances in the cellular biology, biochemistry, and molecular biology of acidocalcisomes

SUMMARYAcidocalcisomes are organelles conserved during evolution and closely related to the so-called volutin granules of bacteria and archaea, to the acidocalcisome-like vacuoles of yeasts, and to the lysosome-related organelles of animal species. All these organelles have in common their acidity and high content of polyphosphate and calcium. They are characterized by a variety of functions from storage of phosphorus and calcium to roles in Ca2+ signaling, osmoregulation, blood coagulation, and inflammation. They interact with other organelles through membrane contact sites or by fusion, and have several enzymes, pumps, transporters, and channels.

Localized Leishmania major infection disrupts systemic iron homeostasis that can be controlled by oral iron supplementation

Leishmania parasites are heavily dependent on efficient iron acquisition from a tightly regulated host iron pool for survival and virulence. Prior studies uncovered multiple strategies adopted by the parasite to hijack the iron-regulatory network of macrophages. Despite these extensive studies with infected macrophages, there is limited knowledge of the effect of Leishmania infection on systemic iron homeostasis. This issue is particularly relevant for Leishmania major, which causes localized skin infection with minimal lymphatic spread. We show for the first time that L. major infection in the mouse footpad induced influx of iron at the site of infection through blood with simultaneous upregulation of transferrin receptor 1 and downregulation of phagolysosomal iron exporter Nramp1 expression in the footpad tissue. Interestingly, localized L. major infection had far-reaching effects beyond the infection site triggering anemia-like symptoms. This was evident from depleted physiological iron stores from the liver and bone marrow as well as reduced hemoglobin levels and deformed erythrocytes. The infected mice also developed splenomegaly with signs of splenic stress erythropoiesis as indicated by upregulation of several erythroid-related genes. These observations prompted us to provide oral iron supplementations to the L. major-infected mice, which resulted in a drastic reduction of the parasite load and restoration of iron homeostasis.

Andrographolide-Soya-L-α-Phosphatidyl Choline Complex Augmented Solubility and Drug Delivery in Leishmania donovani, a Causative Agent for Cutaneous and Visceral Leishmaniasis

The utility of andrographolide (AN) in visceral leishmaniasis (VL) and cutaneous leishmaniasis (CL) is limited owing to poor solubility, hindered permeation, and unstable structure under physiological conditions. The present study mainly focuses on synthesizing of andrographolide-Soya-L-α-phosphatidyl choline (ANSPC) complex in ethanol and its characterization using various spectral and analytical techniques. Results from FT-IR, ¹H NMR, ROSEY, and in silico docking techniques suggest ANSPC complex formation due to inter-molecular interaction between the hydrophilic head of SPC and hydroxyl group of AN present at 24th position. ANSPC complex demonstrated the solubility of 113.93 ± 6.66 μg/mL significantly (P < 0.05) greater than 6.39 ± 0.47 μg/mL of AN. The particle size of ANSPC complex was found to be 182.2 ± 2.69 nm. The IC₅₀ value of AN suspension (PBS, pH ~ 7.4) at 24, 48, and 72 h against Leishmania donovani (L. donovani) was noticed to be 32.76 ± 4.53, 20.87 ± 2.37, and 17.71 ± 3.06 μM/mL, respectively. Moreover, augmented aqueous solubility of ANSPC complex led to significant (P < 0.05) reduction in IC₅₀ value, i.e., 25.02 ± 4.35, 11.31 ± 0.60, and 8.33 ± 2.71 μM/mL at 24, 48, and 72 h, respectively. The IC₅₀ values for miltefosine were noted to be 9.84 ± 2.65, 12.13 ± 7.26, and 6.56 ± 0.61 μM/mL at similar time periods. Moreover, ANSPC complex demonstrated augmented cellular uptake at 24 h as compared to 6 h in L. donovani. We suppose that submicron size and phospholipid-mediated complexation might have endorsed the permeation of ANSPC complex across the plasma membrane of L. donovani parasite by transport mechanisms such as P-type ATPase. ANSPC complex warrants further in-depth in vivo studies under a set of stringent parameters for translating the product into a clinically viable form.

Copper Metabolism in Naegleria gruberi and Its Deadly Relative Naegleria fowleri

Although copper is an essential nutrient crucial for many biological processes, an excessive concentration can be toxic and lead to cell death. The metabolism of this two-faced metal must be strictly regulated at the cell level. In this study, we investigated copper homeostasis in two related unicellular organisms: nonpathogenic Naegleria gruberi and the “brain-eating amoeba” Naegleria fowleri. We identified and confirmed the function of their specific copper transporters securing the main pathway of copper acquisition. Adjusting to different environments with varying copper levels during the life cycle of these organisms requires various metabolic adaptations. Using comparative proteomic analyses, measuring oxygen consumption, and enzymatic determination of NADH dehydrogenase, we showed that both amoebas respond to copper deprivation by upregulating the components of the branched electron transport chain: the alternative oxidase and alternative NADH dehydrogenase. Interestingly, analysis of iron acquisition indicated that this system is copper-dependent in N. gruberi but not in its pathogenic relative. Importantly, we identified a potential key protein of copper metabolism of N. gruberi, the homolog of human DJ-1 protein, which is known to be linked to Parkinson’s disease. Altogether, our study reveals the mechanisms underlying copper metabolism in the model amoeba N. gruberi and the fatal pathogen N. fowleri and highlights the differences between the two amoebas.