Biophysical Society Thematic Meeting | Hamburg 2022

Biophysics at the Dawn of Exascale Computers

Poster Abstracts

46-POS Board 46 FORMATION OF RING AND SLIT SHAPED GASDERMIN-D PORES IN PLASMA MEMBRANES Stefan L Schäfer 1 ; Gerhard Hummer 1,2 ; 1 Max-Planck-Institute of Biophysics, Theoretical Biophysics, Frankfurt am Main, Germany 2 Goethe University Frankfurt, Institute of Biophysics, Frankfurt am Main, Germany Gasdermins execute the final step in pyroptosis, a highly regulated form of lytic cell death associated with inflammation. After activation by caspases, the N-terminal domain of gasdermin- D (GSDMD NT ) binds to the plasma membrane, assembles into large homo-oligomers and inserts a β - sheet into the membrane. The hydrophobic face of the β -sheet faces the plasma membrane and the hydrophilic face repels the hydrophobic core of the membrane to facilitate pore formation. The exact sequence of events and the detailed mechanisms of membrane binding, conformational rearrangements, assembly, and insertion of the β -sheet remain elusive. To gain insight into the dynamics and stability of the large gasdermin complex with an outer diameter of more than 30 nm, we performed multi-microsecond atomistic molecular dynamics simulations of the GSDMD NT in its 33-mer pore and prepore conformations. Both structures tightly interacted with the acidic phospholipids of the intracellular leaflet. Whereas GSDMD NT in pore conformation maintained a nearly perfect circular shape and was stable in a flat membrane, the ring in prepore conformation deformed the membrane. Motivated by atomic force microscopy (AFM) images, we also performed simulations of GSDMD NT monomers and differently sized oligomers in pore conformation. In all cases, the β -sheets stayed stably inserted in the membrane and formed water-filled membrane pores. Larger oligomers transitioned into the slit and ring shaped pores seen in AFM experiments. We conclude that already small oligomers can sustain stable membrane insertions, and that the oligomers can reorganize into slits and robust circular pores.

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