On 2013 Nov 21, Gary Ward commented:

This report describes a simple yet elegant series of experiments demonstrating that the T. gondii parasitophorous vacuole membrane (PVM) acts as a sieve, allowing small molecules (up to ~1300 Da) to pass from the cytosol into the vacuolar space. The researchers microinjected a panel of fluorescent probes either into the cytosol of infected cells or into the parasitophorous vacuole and observed bi-directional, passive transport across the PVM. These experiments provided an important new insight into the interface between the intracellular parasite and the host cell. The likely presence of nonselective membrane channels in the PVM is analogous to the outer membrane of Gram-negative bacteria, in which membrane porins allow passive transport of nutrients and metabolites into the bacterial periplasmic space.

These results from these experiments are consistent with characterization of the vacuole membrane in host cells infected with the related apicomplexan parasites, Plasmodium falciparum [Desai et al, Nature 362 (1993); Desai and Rosenberg, PNAS 94 (1997)] and Eimeria nieschulzi [Werner-Meier and Entzeroth, Parasitol Res 83 (1997)]. The obligate intracellular microsporidian Encephalitozoon cuniculi also resides within an intracellular vacuole capable of passive transport of fluorescent peptides up to 1100 Da while 10 kDa fluorescently-labeled dextrans are excluded [Rönnebäumer et al, Eukaryot Cell 7 (2008)]. The presence of non-selective membrane channels and the non-fusogenic nature of the parasitic vacuoles established by these phylogenetically distant organisms point to a similar adaptation to an intracellular parasitic lifestyle.

Posted by Gary Ward on behalf of the University of Vermont Toxoplasma Journal Club (UVM ToxoJC); members include Jenna Foderaro, Anne Kelsen, Shruthi Krishnamurthy, Jacqueline Leung, Pramod Rompikuntal, Luke Tilley & Gary Ward

On 2013 Nov 21, Gary Ward commented:

This report describes a simple yet elegant series of experiments demonstrating that the T. gondii parasitophorous vacuole membrane (PVM) acts as a sieve, allowing small molecules (up to ~1300 Da) to pass from the cytosol into the vacuolar space. The researchers microinjected a panel of fluorescent probes either into the cytosol of infected cells or into the parasitophorous vacuole and observed bi-directional, passive transport across the PVM. These experiments provided an important new insight into the interface between the intracellular parasite and the host cell. The likely presence of nonselective membrane channels in the PVM is analogous to the outer membrane of Gram-negative bacteria, in which membrane porins allow passive transport of nutrients and metabolites into the bacterial periplasmic space.

These results from these experiments are consistent with characterization of the vacuole membrane in host cells infected with the related apicomplexan parasites, Plasmodium falciparum [Desai et al, Nature 362 (1993); Desai and Rosenberg, PNAS 94 (1997)] and Eimeria nieschulzi [Werner-Meier and Entzeroth, Parasitol Res 83 (1997)]. The obligate intracellular microsporidian Encephalitozoon cuniculi also resides within an intracellular vacuole capable of passive transport of fluorescent peptides up to 1100 Da while 10 kDa fluorescently-labeled dextrans are excluded [Rönnebäumer et al, Eukaryot Cell 7 (2008)]. The presence of non-selective membrane channels and the non-fusogenic nature of the parasitic vacuoles established by these phylogenetically distant organisms point to a similar adaptation to an intracellular parasitic lifestyle.

Posted by Gary Ward on behalf of the University of Vermont Toxoplasma Journal Club (UVM ToxoJC); members include Jenna Foderaro, Anne Kelsen, Shruthi Krishnamurthy, Jacqueline Leung, Pramod Rompikuntal, Luke Tilley & Gary Ward