MSc Exit Seminar – Mathieu Poirier (Harrison lab)

MSc Exit Seminar

Friday January 6^th, 2:10 pm – Room SW 403, University of Toronto at Scarborough

Mathieu Poirier (Harrison lab)

“Characterization of F-actin flashes on phagosomes in macrophages”

Abstract

Macrophages are specialised leukocytes tasked with the engulfment and destruction of foreign particles. We are studying particle uptake by the CR3 receptor in macrophages. Post particle internalization, we have shown that F-actin localizes transiently at phagosome membranes and this event, termed F-actin flashing, often results in red blood cell deformation, lysis and occasionally fission, suggestive of a force-generating property. Putative mechanosensing properties were also proposed based on identification of certain phagosome membrane-localized proteins, as well as distinctions in temporal dynamics based on the internalized particle’s malleability. We have also reported that certain stages of maturation were delayed in phagosomes exhibiting F-actin flashing. Finally, inhibiting myosin IIA activity significantly reduced the frequency at which red blood cell-containing phagosomes became deformed simultaneously with transient F-actin accumulation. Actomyosin-driven contractions could serve to physically distort malleable particles, akin to “chewing”, which may have implications in phagosome maturation, as well as antigen presentation.