Pyroptotic executioner pore-forming protein GSDMD forms oligomeric assembly and exhibits amyloid-like attributes that could contribute for its pore-forming function.

Abstract

Gasdermin D (GSDMD) is the chief executioner of inflammatory cell death or pyroptosis. During pyroptosis, proteolytic processing of GSDMD releases its N-terminal domain (NTD), which then forms large oligomeric pores in the plasma membranes. Membrane pore-formation by NTD allows the release of inflammatory cytokines and causes membrane damage to induce cell death. Structural mechanisms of GSDMD-mediated membrane pore-formation have been extensively studied. However, less effort has been made to understand the physicochemical properties of GSDMD and their functional implications. Here, we explore detailed characterization of the physicochemical properties of mouse GSDMD (mGSDMD), and their implications in regulating the pore-forming function. Our study reveals that mGSDMD shows some of the hallmark features of amyloids, and forms oligomeric assemblies in solution that are critically dependent on the disulphide bond-forming ability of the protein. mGSDMD oligomeric assemblies do not resemble typical amyloid fibrils/aggregates, and do not show resistance to proteolytic degradation that is otherwise observed with the conventional amyloids. Our results further elucidate the essential role of an amyloid-prone region (APR) in the oligomerization and amyloid-like features of mGSDMD. Furthermore, alteration of this APR leads to compromised pore-forming ability and cell-killing activity of NTD released from mGSDMD. Taken together, our study for the first time provides crucial new insights regarding implications of the amyloid-like property of mGSDMD in regulating its pore-forming function, which is an essential requirement for this pyroptotic executioner. To the best of our knowledge, such mode of regulation of mGSDMD-function has not been appreciated so far.