Institut de Biologie StructuraleGrenoble / France

Study of the phagocytic synapse at the nanoscale

This project conducted by P. Frachet, P. Tacnet, and S. Dufour (Ph.D. student), is dedicated to characterizing the apoptotic cell-macrophage interface during the phagocytosis process, employing super-resolution imaging, (i.e. dSTROM, PALM and sptPALM ). Our main objective is to reveal at the nanoscale the dynamic architecture of the molecular complexes that organize the contact between the apoptotic cell and the macrophage. Based on our knowledge in the field of the clearance of apoptotic cells (see references below), we focus on specific molecules that are involved in the recognition/tethering stage of altered-self cells by phagocytes and that are implicated in the upcoming downstream signaling events.

Schematic illustration of the involvement of various eat-me (CRT, PS) or don’t eat me (CD47) signals participating to the phagocytic synapse

Keys methods used : eukaryotic cells culture, phagocytosis assays, flow cytometry and fluorescence microscopy. We also gather methodological and fundamental skills in structural biochemistry of proteins, including interaction analysis by Surface Plasmon Resonance (SPR).
Our ongoing project, is currently being extended to also study the phagocytosis of cancer cells when treated to induce their apoptosis, in close collaboration with F. Hans and J. Timmins of the DDR team, within the I2SR group.

References
Calreticulin Release at an Early Stage of Death Modulates the Clearance by Macrophages of Apoptotic Cells. Osman, R. ; Tacnet-Delorme, P. ; Kleman, J.-P. ; Millet, A. ; Frachet, P. Frontiers in Immunology 2017, 8. doi.10.3389/fimmu.2017.01034. Open
Molecular and cellular interactions of scavenger receptor SR-F1 with complement C1q provide insights into its role in the clearance of apoptotic cells Wicker-Planquart, C. ; Dufour, S. ; Tacnet-Delorme, P. ; Bally, I. ; Delneste, Y. ; Frachet, P. ; Housset, D. ; Thielens, N. M. Front. Immunol. 2020, 11. doi. 10.3389/fimmu.2020.00544. Open
Proteinase 3 Interferes With C1q-Mediated Clearance of Apoptotic Cells. Tacnet-Delorme P ; Gabillet J ; Chatfield S ; Thieblemont N ; Frachet P* ; Witko-Sarsat V. Front Immunol. 2018 April DOI : 10.3389/FIMMU.2018.00818. Open
Relative Contribution of C1q and Apoptotic Cell-Surface Calreticulin to Macrophage Phagocytosis. Verneret M, Tacnet-Delorme P, Osman R, Awad R, Grichine A, Kleman JP, Frachet P*. J Innate Immun. 2014 Feb 15
Role of C1q in efferocytosis and self-tolerance : links with autoimmunity. Book title : Autoimmunity - Pathogenesis of Autoimmune Diseases, Clinical Aspects and Therapy of Specific Autoimmune Diseases (ISBN 978-953-51-4188-4) edited by : Dr. Katerina Chatzidionysiou. Philippe Frachet*, Pascale Tacnet-Delorme, Christine Gaboriaud and Nicole Thielens. Intech 2015 DOI : 10.5772/60519