Anticancer Activity and Mechanisms of Action of MAPK pathway inhibitors

The localization of PbATG8 to the apicoplast was partial (but not exclusive) because PbATG8-associated gold particles were also detected on unidentified tubules and vesicles in the cytoplasm

The localization of PbATG8 to the apicoplast was partial (but not exclusive) because PbATG8-associated gold particles were also detected on unidentified tubules and vesicles in the cytoplasm. structures before expulsion from the parasite. Interference with PbATG8 function by overexpression results in poor development into late liver stages and production of small merosomes that contain immature merozoites unable to initiate a blood infection. At the cellular level, PbATG8-overexpressing exhibits a delay in microneme compartmentalization into PbATG8-containing autophagosomes and elimination compared to parasites from the parental strain. The apicoplast, identifiable by immunostaining of the acyl carrier protein (ACP), undergoes an abnormally fast proliferation in mutant parasites. Over time, MW-150 dihydrochloride dihydrate the ACP staining becomes diffuse in merosomes, indicating a collapse of the apicoplast. PbATG8 is not incorporated into the progeny of mutant parasites, in contrast to parental merozoites in which PbATG8 and ACP localize to the apicoplast. These observations reveal that ATG8 is a key effector in the development of merozoites by controlling microneme clearance and apicoplast proliferation and that dysregulation in ATG8 levels is detrimental for malaria infectivity. IMPORTANCE Malaria is responsible for more mortality than any other parasitic disease. Resistance to antimalarial medicines is a recurring problem; new drugs are urgently needed. A key to the parasites successful intracellular MW-150 dihydrochloride dihydrate development in the liver is the metabolic changes necessary to convert the parasite from a sporozoite to a replication-competent, metabolically active trophozoite form. Our study reinforces the burgeoning concept that organellar changes during parasite differentiation are mediated by an autophagy-like process. We have identified ATG8 in liver forms as an important effector that controls the development and fate of organelles, e.g., the clearance of micronemes that are required for hepatocyte invasion and the expansion of the apicoplast that produces many metabolites indispensable for parasite replication. Given the unconventional properties and the importance of ATG8 for parasite development in hepatocytes, targeting the parasites autophagic pathway may represent a novel approach to control malarial infections. INTRODUCTION Malaria parasite species that infect humans must first take up residence in hepatocytes before invading red blood cells, which initiates the pathology associated with malaria. sporozoites are deposited in the host skin by infected mosquitoes. Early events in the biology of sporozoite infection have been well investigated, including the transmigration through tissues and invasion of hepatocytes (1, 2). However, much less is known about the events that occur after hepatocyte invasion, beginning with the phenotypic transformation of sporozoites into trophozoites. A key to the parasites successful intracellular development in the liver is the morphological and metabolic changes required for the sporozoite-to-trophozoite conversion. We previously showed that concomitantly with their change in shape from elongated sporozoite to round trophozoite, converting parasites expel their micronemes, organelles needed for motility or MW-150 dihydrochloride dihydrate invasion and thus useless for parasite replication (3). Autophagy is the archetypal disposal pathway for keeping the cell interior clean of disused and superfluous organelles (4). We illustrated that parasites sequester micronemes into double-membrane vesicles resembling autophagosomes, suggesting that an autophagy-like process is activated during parasite conversion in the liver. In contrast to mammalian cells and yeast that contain ~40 autophagy-related genes (ATG), the malaria parasite contains ~15 orthologs of ATG identified by comparative studies: those whose products are required for vesicle expansion and completion are present, while genes involved in induction of autophagy and cargo packaging are mostly absent (5,C9). All the components of the ubiquitin-like ATG8 system, which are involved in autophagosome formation, are expressed by orthologs of ATG8, ATG3, and ATG7 (10). Interestingly, coexpression of PbATG8, PbATG3, and PbATG7 is upregulated during Mouse monoclonal to PRMT6 early sporozoite differentiation in liver cells. In liver forms of liver forms may exploit the ATG8 conjugation pathway to mediate the elimination of unwanted organelles such as micronemes by autophagy and, that the apicoplast may be the lipid provider to generate autophagosomes sequestering micronemes. Otherwise, the single ATG8 in may perform several functions within the parasite. The mammalian LC3 homologs -GABARAP and GATE-16 participate in vesicular transport from the endoplasmic reticulum (ER) to the Golgi apparatus and within the Golgi apparatus (17). PbATG8-labeled vesicles distributed throughout the cytoplasm suggest that PbATG8 also plays such a role in facilitating vesicular transport of lipids to the apicoplast, contributing to the shape change and size expansion of this organelle that occur during the intrahepatic development of is also localized to the apicoplast, and it seems to be involved in the maintenance of this organelle.