Integrated mechanobiology of integrin-mediated phagocytosis
Project: Integrated mechanobiology of integrin-mediated phagocytosis
Laboratory: Team Biology of Phagocytes
Affiliation: Institut Cochin (Inserm U1016, CNRS UMR8104, Université Paris Descartes)
Address: Institut Cochin, 22, rue Méchain 75014 Paris
Name: Pierre-Olivier Couraud (Director of Institut Cochin); Florence Niedergang (Team leader)
Phone number: 0140516401
Name: Florence Niedergang (team leader) and Anna Mularski (post-doctoral researcher with a physics/chemisty background)
Phone number: 0140516421
Subject Keywords: Phagocytosis
Traction force microscopy
Summary of lab’s interests: The laboratory has a long time interest in phagocytosis, the mechanism of uptake and degradation of invading microorganisms or debris that is crucial for bacterial clearance and the resolution of inflammation. Our first goal is to dissect the mechanisms used by phagocytes, in particular the coordinated activities of signaling pathways, membrane trafficking and cytoskeleton dynamics. Second, we analyze how viral infection of macrophages impair their phagocytic functions and hence promote the development of bacterial superinfections. Finally, we explore how some phagocytes regurgitate non-degraded material to activate B cells in order to manipulate the immune response.
Project summary: During phagocytosis, actin polymerization drives membrane deformation and phagosome cup formation, which is further modulated by the mechanics of the particle itself. The project focuses on actin-binding proteins, as mechanosensitive hubs at the center of feedback loops that control anchoring to the actin cytoskeleton and activation of the integrins during phagocytosis.
The lab has recently adapted a three-dimensional phagocytosis assay to study phagosome formation and closure in living cells based on Total Internal Reflection Fluorescence Microscopy (TIRFM) to visualize the tips of extending pseudopods, as well as the base of the forming phagosome.
The PhD candidate will participate in the development of a novel ‘4D’ microscopy – including an innovative traction force microscopy (TFM) element – that reports on both spatial-temporal localization of the key players and the force distribution around the phagosome in macrophages. For this, deformable acrylamide surfaces coated with opsonized particles are used. With a precise knowledge of the material properties of these substrates, cellular traction forces can be calculated.
Cell biology and biochemistry work has already allowed the team to identify new potential actin regulators. The relative contribution of these factors to phagocytosis will be assessed by functional inhibition or expression of mutants.
Interdisciplinary aspect of the project: The project is performed in collaboration with Christophe Le Clainche (I2BC, Gif-sur-Yvette) who developed an elegant in vitro microscopy assay, to reconstitute and characterise the actomyosin-dependent mechanosensitive machineries with pure proteins on geometrically-defined micropatterned surfaces. This collaboration has enabled the identification of previously unknown actin binding partners active during integrin-mediated phagocytosis. The host lab has started to develop an original traction force microscopy method to analyse phagocytosis by macrophages, in addition to classical cell biology approaches. The project is part of an ambitious project that includes theoretical modelling of integrin-mediated phagocytosis by Jian Liu (NIH, USA).