Not quite FedEx: How are venom proteins packaged for delivery by the parasitoid wasp Ganaspis hookeri?
Authors: Nicholas Bretz; Chris Lark; Nathan Mortimer
Affiliation: Illinois State University
Keywords: k. host/pathogen interactions; c. endocytosis
Parasitoid wasps are common pathogens of Drosophila melanogaster, and use venom proteins in order to overcome fly immunity.Venom proteins derived from the parasitoid wasp species Ganaspis hookeri alter the immune response mounted by immune cells known as plasmatocytes within infected D. melanogaster larvae. This venom activity is mediated by a unique venom-specific isoform of the SERCA (Sarco/endoplasmic reticulum Ca2+-ATPase) calcium pump. Venom SERCA activity inhibits the calcium burst normally mounted by plasmatocytes following infection, rendering them unable to melanize the foreign wasp egg. The mechanism by which SERCA and other venom proteins are transported into the host is not completely understood, but preliminary evidence suggests that venom proteins are packaged into venom-specific vesicles known as venosomes. These venosomes allow venom proteins to gain access to plasmatocytes likely via the interaction between virulence factors present on venosomes and host factors on the surface of plasmatocytes. Ultracentrifugation of G. hookeri venom separates venom proteins into unique fractions. Experiments utilizing nanoparticle tracking analysis and dynamic light scattering suggest that two of these fractions are composed of a heterogenous mix of vesicles, further supporting the idea that venoms can be stored as cargo within venosomes. With this, we are using fluorescence labeling of putative venosomes, mass spectrometry and SERCA activity assays to further characterize the venom transport mechanism. Vesicle packaging and specified targeting is a burgeoning field of research with potential applications in drug delivery for disease treatment.