Anthony Sinai, Ph.D.

Associate Professor

Selected publications

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Research statement: Intracellular pathogens like the protozoan parasite Toxoplasma gondii subvert host cell functions to establish a successful infection. The parasite infects nucleated cells of all arm blooded animals and replicates within a specialized parasite modified compartment termed the parasitophorous vacuole (PV). The PV is delimited from the host cytoplasm by the PV membrane (PVM), a unique and poorly understood organelle. As the primary interface between the parasite and host it is presumed and shown to to possess multiple functions including nutrient acquisition and manipulation of host functions. My laboratory is interested in identifying the molecular and cell biological processes underlying T. gondii infection of mammalian cells.

We are primarily interested in defining the molecular basis for the inhibition of host cell apoptosis in Toxoplasma infected cells. This inhibition is manifest as the failure in the activation of the apoptotic cascade within infected cells in response to normally apoptogenic triggers. Our studies indicate multiple sites of interference along both the death receptor as well as the mitochondrial pathways.

We further have identified a critical role for gene expression directed by the host transcription factor NFkB. NFkB is involved in the regulation of a number of genes involved primarily in the pro-survival/ anti-apoptotic response. Remarkably, Toxoplasma appears to completely bypass the conventional mechanism for the activation of NFkB transcription. In contrast to every other inducing stimulus, the T. gondii-mediated signal does not appear to require the host kinase (I kappa B kinase, IKK) responsible for phosphorylating the inhibitor of NFkB (IkB) an event required for degradation of the inhibitor and nuclear translocation leading to transcription. Toxoplasma appears to bypass the requirement by elaborating a distinct IKK activity of likely parasite origin in the PVM. We are currently focusing on identifying this unique activity which would likely make an attractive target for therapeutic intervention.

The Toxoplasma PVM is unusual in its recruitment of host mitochondria and endoplasmic reticulum to for intimate highly stable interactions. Given the role of mitochondria in apoptosis, we are examining the role of manipulation of both PVM-associated and non-associated mitochondria in the establishment of the anti-apoptotic state in infected cells. Our studies indicate clear inhibition of the triggering event in apoptosis, the release of cytochrome c and well at least one step downstream in the cascade. We are dissecting the contribution of both host and parasite factors to the blockade of apoptosis mediated by Toxoplasma infection.

In addition to the focus on the manipulation of host apoptosis we have also undertaken a detailed molecular and analysis of the Toxoplasma PVM. We are initiating a detailed proteomic analysis of the PVM toward identifying novel activities within this unique organelle. We believe the application of innovative approaches combining cell biological, biochemical and molecular-genetic approaches to study the fascinating interface between pathogen and host will lead to the identification of novel mechanisms in microbial pathogenesis.