The Spatiotemporal Dynamics and Membranous Features of the Plasmodium Liver Stage Tubovesicular Network

Abstract

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. This strategy revealed previously unrecognized dynamics with which these membranes extend throughout the host cell. We observed dynamic vesicles, elongated clusters of membranes and long tubules that rapidly extend and contract from the PVM in a microtubule-dependent manner.Live microscopy, correlative light-electron microscopy and fluorescent recovery after photobleaching enabled a detailed characterization of these membranous features, including velocities, the distribution of UIS4 and IBIS1, and the connectivity of PVM and TVN. Labeling of host cell compartments revealed association of late endosomes and lysosomes with the elongated membrane clusters. Moreover, the signature host autophagosome protein LC3 was recruited to the PVM and TVN and colocalized with UIS4. Together, our data demonstrate that the membranes surrounding intrahepatic Plasmodium are involved in active remodeling of host cells.

Feeling at home from arrival to departure: protein export and host cell remodelling duringPlasmodiumliver stage and gametocyte maturation

“…While the UIS4 and IBIS1 signals overlap on the PVM and LSTVN membranes (Ingmundson et al, 2012), proportions of vesicles and tubules are positive only for either UIS4 or IBIS1 (Grützke et al, 2014), indicating that the LSTVN is a complex network of dynamic membranes with nonhomogeneous protein compositions.…”

“…Remarkably, IBIS1 is expressed in both blood and liver stages, but displays distinct spatial patterns in both phases. In the host erythrocyte, IBIS1 is exported and localizes to punctate and highly dynamic structures in the cytoplasm, whereas during liver-stage development, IBIS1 is retained at the PVM and also localizes to the liver stage-tubovesicular network (LSTVN), which includes membranous extensions from the PVM and autonomous vesicular structures in the host cell (Grützke et al, 2014). Absence of IBIS1 results in impairment of blood-stage growth, but no apparent defects in liver-stage development (Ingmundson et al, 2012).…”

“…Fluorescent tagging of the LSTVN-resident proteins UIS4 and IBIS1 allowed live imaging during infection of the LSTVN (Grützke et al, 2014), which was found to be composed of three distinct membrane compartments, (i) elongated tubulovesicular structures emanating from the parasite, (ii) vesicles that travel throughout the host cell and (iii) distinct tubules that rapidly extend from and retract back to the PVM. While the UIS4 and IBIS1 signals overlap on the PVM and LSTVN membranes (Ingmundson et al, 2012), proportions of vesicles and tubules are positive only for either UIS4 or IBIS1 (Grützke et al, 2014), indicating that the LSTVN is a complex network of dynamic membranes with nonhomogeneous protein compositions.…”

Long-term live imaging reveals cytosolic immune responses of host hepatocytes againstPlasmodiuminfection and parasite escape mechanisms

“…3 Balb/c and 3 C57B/6 mice were used per condition, and infected with varying doses of sporozoites, ranging from 5x10 4 to 2x10 5 indicated developmental stage. Scale bars: 10 µm.…”

Plasmodium berghei EXP-1 interacts with host Apolipoprotein H during Plasmodium liver-stage development

“…However, little is known about intrahepatic Plasmodium stages with regard to interactions between the parasite and the host hepatocyte and their potential for nutrient uptake and/or exchange. Small molecules (up to 800 Da) can cross the PVM freely via specialized transport channels (14), whereas larger molecules might reach the parasite via association and possibly fusion of late endosomes, lysosomes, or amphisomes with the PVM (15)(16)(17)(18)(19).…”