Harnessing cholesterol uptake of malaria parasites for therapeutic applications.

Parasites, such as the malaria parasite P. falciparum, are critically dependent on host nutrients. Interference with nutrient uptake can lead to parasite death and, therefore, serve as a successful treatment strategy.

Moving on: How malaria parasites exit the liver.

An essential step in the life cycle of malaria parasites is their egress from hepatocytes, which enables the transition from the asymptomatic liver stage to the pathogenic blood stage of infection. To exit the liver, Plasmodium parasites first disrupt the parasitophorous vacuole membrane that surrounds them during their intracellular replication. Subsequently, parasite-filled structures called merosomes emerge from the infected cell.

Absence of PEXEL-Dependent Protein Export in Liver Stages Cannot Be Restored by Gain of the HSP101 Protein Translocon ATPase.

Host cell remodeling is critical for successful replication inside erythrocytes and achieved by targeted export of parasite-encoded proteins. In contrast, during liver infection the malarial parasite appears to avoid protein export, perhaps to limit exposure of parasite antigens by infected liver cells. HSP101, the force-generating ATPase of the protein translocon of exported proteins (PTEX) is the only component that is switched off during early liver infection.

Conservation of S20 as an Ineffective and Disposable IFNγ-Inducing Determinant of Sporozoites Indicates Diversion of Cellular Immunity.

Despite many decades of research to develop a malaria vaccine, only one vaccine candidate has been explored in pivotal phase III clinical trials. This candidate subunit vaccine consists of a portion of a single antigen, circumsporozoite protein (CSP). This antigen was initially identified in the murine malaria model and shown to contain an immunodominant and protective CD8 T cell epitope specific to the H-2K (BALB/c)-restricted genetic background.

A Plasmodium cysteine protease required for efficient transition from the liver infection stage.

The transitions between developmental stages are critical points in the Plasmodium life cycle. The development of Plasmodium in the livers of their mammalian hosts bridges malaria transmission and the onset of clinical symptoms elicited by red blood cell infection. The egress of Plasmodium parasites from the liver must be a carefully orchestrated process to ensure a successful switch to the blood stage of infection.

The Plasmodium liver-stage parasitophorous vacuole: A front-line of communication between parasite and host.

The intracellular development and differentiation of the Plasmodium parasite in the host liver is a prerequisite for the actual onset of malaria disease pathology. Since liver-stage infection is clinically silent and can be completely eliminated by sterilizing immune responses, it is a promising target for urgently needed innovative antimalarial drugs and/or vaccines. Discovered more than 65 years ago, these stages remain poorly understood regarding their molecular repertoire and interaction with their host cells in comparison to the pathogenic erythrocytic stages.

Sequestration of cholesterol within the host late endocytic pathway restricts liver-stage development.

While lysosomes are degradative compartments and one of the defenses against invading pathogens, they are also hubs of metabolic activity. Late endocytic compartments accumulate around liver-stage parasites during development, and whether this is a host defense strategy or active recruitment by the parasites is unknown. In support of the latter hypothesis, we observed that the recruitment of host late endosomes (LEs) and lysosomes is reduced in parasites, which lack a parasitophorous vacuole membrane protein and arrest during liver-stage development.

The Plasmodium berghei translocon of exported proteins reveals spatiotemporal dynamics of tubular extensions.

The erythrocyte is an extraordinary host cell for intracellular pathogens and requires extensive remodelling to become permissive for infection. Malaria parasites modify their host red blood cells through protein export to acquire nutrients and evade immune responses. Endogenous fluorescent tagging of three signature proteins of the Plasmodium berghei translocon of exported proteins (PTEX), heat shock protein 101, exported protein 2 (EXP2), and PTEX88, revealed motile, tubular extensions of the parasitophorous vacuole that protrude from the parasite far into the red blood cell.

Trafficking of the signature protein of intra-erythrocytic Plasmodium berghei-induced structures, IBIS1, to P. falciparum Maurer's clefts.

Remodeling of the host red blood cell by Plasmodium falciparum is well established and crucial for infection and parasite virulence. Host cell modifications are not exclusive to human Plasmodium parasites and also occur in hepatocytes and erythrocytes infected with murine Plasmodium parasites. The recently described intra-erythrocytic P.

In Vivo Function of PTEX88 in Malaria Parasite Sequestration and Virulence.

Malaria pathology is linked to remodeling of red blood cells by eukaryotic Plasmodium parasites. Central to host cell refurbishment is the trafficking of parasite-encoded virulence factors through the Plasmodium translocon of exported proteins (PTEX). Much of our understanding of its function is based on experimental work with cultured Plasmodium falciparum, yet direct consequences of PTEX impairment during an infection remain poorly defined.

The spatiotemporal dynamics and membranous features of the Plasmodium liver stage tubovesicular network.

For membrane-bound intracellular pathogens, the surrounding vacuole is the portal of communication with the host cell. The parasitophorous vacuole (PV) harboring intrahepatocytic Plasmodium parasites satisfies the parasites' needs of nutrition and protection from host defenses to allow the rapid parasite growth that occurs during the liver stage of infection. In this study, we visualized the PV membrane (PVM) and the associated tubovesicular network (TVN) through fluorescent tagging of two PVM-resident Plasmodium berghei proteins, UIS4 and IBIS1.

Feeling at home from arrival to departure: protein export and host cell remodelling during Plasmodium liver stage and gametocyte maturation.

Obligate intracellular pathogens actively remodel their host cells to boost propagation, survival, and persistence. Plasmodium falciparum, the causative agent of the most severe form of malaria, assembles a complex secretory system in erythrocytes. Export of parasite factors to the erythrocyte membrane is essential for parasite sequestration from the blood circulation and a major factor for clinical complications in falciparum malaria.

The exported Plasmodium berghei protein IBIS1 delineates membranous structures in infected red blood cells.

The importance of pathogen-induced host cell remodelling has been well established for red blood cell infection by the human malaria parasite Plasmodium falciparum. Exported parasite-encoded proteins, which often possess a signature motif, termed Plasmodium export element (PEXEL) or host-targeting (HT) signal, are critical for the extensive red blood cell modifications. To what extent remodelling of erythrocyte membranes also occurs in non-primate hosts and whether it is in fact a hallmark of all mammalian Plasmodium parasites remains elusive.

Analyzing association of the endoplasmic reticulum with the legionella pneumophila-containing vacuoles by fluorescence microscopy.

A unique feature of the intracellular life cycle of Legionella pneumophila is the interaction between the vacuole in which L. pneumophila resides and the endoplasmic reticulum of the host cell. This interaction is crucial for L.

Legionella pneumophila proteins that regulate Rab1 membrane cycling.

Rab1 is a GTPase that regulates the transport of endoplasmic-reticulum-derived vesicles in eukaryotic cells. The intracellular pathogen Legionella pneumophila subverts Rab1 function to create a vacuole that supports bacterial replication by a mechanism that is not well understood. Here we describe L.

The Legionella pneumophila effector protein DrrA is a Rab1 guanine nucleotide-exchange factor.

The intracellular pathogen Legionella pneumophila avoids fusion with lysosomes and subverts membrane transport from the endoplasmic reticulum to create an organelle that supports bacterial replication. Transport of endoplasmic reticulum-derived vesicles to the Legionella-containing vacuole (LCV) requires bacterial proteins that are translocated into host cells by a type IV secretion apparatus called Dot/Icm. Recent observations have revealed recruitment of the host GTPase Rab1 to the LCV by a process requiring the Dot/Icm system.

The structure of RalF, an ADP-ribosylation factor guanine nucleotide exchange factor from Legionella pneumophila, reveals the presence of a cap over the active site.

The Legionella pneumophila protein RalF is secreted into host cytosol via the Dot/Icm type IV transporter where it acts to recruit ADP-ribosylation factor (Arf) to pathogen-containing phagosomes in the establishment of a replicative organelle. The presence in RalF of the Sec7 domain, present in all Arf guanine nucleotide exchange factors, has suggested that recruitment of Arf is an early step in pathogenesis. We have determined the crystal structure of RalF and of the isolated Sec7 domain and found that RalF is made up of two domains.