ADAM10-Lipid interactions during apoptosis

NAISS 2024/5-71


NAISS Medium Compute

Principal Investigator:

Erdinc Sezgin


Karolinska Institutet

Start Date:


End Date:


Primary Classification:

10601: Structural Biology



Efferocytosis is essential for organismal development, tissue homeostasis and elimination of pathogen-infected cells. T cells are central to the adaptive immune response and are tightly regulated by apoptotic cell death during thymic education and subsequent clonal proliferation. Transmembrane mucins are extended, highly glycosylated molecules within the glycocalyx that modulate intercellular interactions and are implicated in transformation. Biochemical data from the Sezgin lab has shown that the induction of apoptosis in both transformed and primary human T cells leads to rapid and selective cell surface removal of mucins by the sheddase ADAM10. Apoptosis-induced loss or genetic knock-out of these mucins enhanced uptake of dying T-cells by macrophages, whereas pharmacologic inhibition or genetic abrogation of ADAM10 function reduced target cell efferocytosis. Mucin expression on T cells thus acts as a protection against phagocytosis, and apoptosis-mediated downregulation of mucin expression by ADAM10 promotes efferocytosis. While the fact that negatively charged lipids need to be exposed to the cell surface for this process to occur is well established, the role of these lipids in ADAM10 sheddase activity is currently unknown. Here we propose an integrative approach to resolve the mechanism of lipid-induced sheddase activation. Processes involving regulation by membrane lipids are inherently difficult to investigate given the complex and dynamic nature of the membrane and the small size of the membrane lipids. Our approach will include three main components: fluorescence and cryo-electron imaging of reconstituted systems of controlled composition, and computational modeling to tie the results together, combining the high spatial resolution of cryo-electron approaches with the dynamics and larger scale of fluorescence microscopy into a coherent mechanistic picture. ADAM10 is a transmembrane protein whose extracellular domain has been characterized in 2017 using crystallography, showing a completely folded structure with an buried catalytic domain. Recently, an open structure of the protein has been characterized using cryo-EM, suggesting that the opening of the protein is essential for its activity. We plan to develop a multiscale model of the ADAM10 protein, using molecular dynamics simulations at the all-atom (AA) and coarse-grained (CG) scales, to characterize the ability of the protein to open depending on the membrane composition. The CG method rely on the gathering of particles into unique beads, reducing the number of interactions to be calculated along the simulation. These calculations will allow us to reach longer timescales which will be instrumental to understand the general organization of the membrane components and their interactions with the protein. However, we will still need a more precise characterization of these interactions, that will be reached using AA simulations, whose starting point will be based on equilibrium states obtained with CG simulations. All the obtained results will be validated against experimental results obtained by using the method described above.