EXAMINING TELEOST LEUKOCYTE IMMUNE-TYPE RECEPTOR MEDIATED INDUCTION OF PHAGOCYTIC TENTACLES
Dustin Lillico, University of Alberta
Dustin Lillico1, James Stafford1
1. Department of Biological Sciences, University of Alberta, Edmonton, Alberta, T6G 2R3
Fundamental for nutrient acquisition in primitive unicellular organisms such as amoeba, phagocytosis has evolved into a complex and important component of innate immunity and tissue homeostasis in all multicellular organisms. To further understand the phagocytic process in vertebrates, my research focuses on characterizing the channel catfish (Ictalurus punctatus) leukocyte immune-type receptor (IpLITR) proteins. In the present study I used IpLITRtransfected rat basophilic leukemia (RBL)-2H3 cells to further compare the phagocytic behavior mediated by IpLITR 2.6b (classical ITAM-dependent pathway) with the novel ITAMindependent pathway evoked by the functionally versatile IpLITR 1.1b protein. The specific goal of this study was to address the hypothesis that IpLITR 1.1b uniquely regulates the deployment of membrane structures called filopodia that may participate in the early stages of phagocytosis. Specifically, using live-cell video imaging of cells co-transfected with LifeAct and highresolution SEM, I show that IpLITR 1.1b-expressing cells generate F-actin dense filopodia-like protrusions during the early stages of the phagocytic process. In addition, these structures retract back towards the cell after target contact to secure captured microspheres on the cell surface. This activity was then followed by distinct F-actin polymerization dynamics leading to the formation of phagocytic cups and in some cases the eventual engulfment of the microspheres. Overall, these results support the hypothesis that IpLITR 1.1b regulates an alternative phagocytic pathway that is functionally distinct from the prototypical pathway observed for IpLITR 2.6b. The molecular mechanisms that regulate the generation of IpLITR-induced phagocytic tentacles are currently being investigated.