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Integrated mechanobiology of integrin-mediated phagocytosis

Integrated mechanobiology of integrin-mediated phagocytosis

By In Aiv Internship On August 6, 2018


Internship title: Integrated mechanobiology of integrin-mediated phagocytosis

LABORATORY
Name: Team Biology of Phagocytes
Affiliation: Institut Cochin (Inserm U1016, CNRS UMR8104, Université Paris Descartes)
Address: 22, rue Méchain, 75014 Paris
E-mail: florence.niedergang@inserm.fr

LAB Director
Name: Florence NIEDERGANG
Phone number: 0033140516421
E-mail: florence.niedergang@inserm.fr

SUPERVISOR
Name: Florence Niedergang and Anna Mularski (post-doctoral researcher with a physics/chemisty background)
Phone number: 0033140516421
E-mail: florence.niedergang@inserm.fr

Subject Keywords: Phagocytosis, Integrins, Traction force microscopy, Actin, Mechanobiology

Tools and methodologies: Cell biology, microscopy, TIRFM, TFM, force measurements
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. One major goal is to dissect the mechanisms used by phagocytes, in particular the coordinated activities of signaling pathways, membrane trafficking and cytoskeleton dynamics. We also study how viral infection of macrophages perturb their phagocytic functions, leading to the development of bacterial superinfections.
Because phagocytosis is the mechanism of internalization of large particles of several microns in size, it involves important mechanical constraints, which have been overlooked. The lab integrates a multidisciplinary approach combining molecular and cell biology with advanced microscopy and physics to study phagosome formation.

Project summary: During phagocytosis, actin polymerization drives membrane deformation and phagosome 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). This approach yields the spatial-temporal localization of proteins during integrin-mediated phagocytosis.

To study the forces during phagosome formation, a new traction force microscopy (TFM) element has been developed, using deformable substrates. With a precise knowledge of the material properties of these substrates, cellular traction forces can be calculated, allowing for the determination of cellular force distribution.
The team has already identified new potential actin regulators. The relative contribution of these factors to force sensing and force generation during phagocytosis will be assessed by functional inhibition or expression of mutants.

The AVI intern would work with a post-doctoral researcher on the recently developed TFM assay to monitor forces during phagocytosis.

The experimental data generated will contribute to a collaborative modeling project.

Interdisciplinary aspect of the project: The project is performed in collaboration with Christophe Le Clainche (I2BC, Gif-sur-Yvette) who characterises mechanosensitive machineries with pure proteins on geometrically-defined micropatterned surfaces.
Importantly, the host lab has developed an original traction force microscopy method to analyse phagocytosis by macrophages, in collaboration with Martial Balland, (Grenoble), in addition to classical cell biology approaches. The project is also part of an ambitious project that includes theoretical modelling of integrin-mediated phagocytosis by Jian Liu (NIH, USA).