Pyroptosis is a form of regulated cell death (RCD) that is characterised by a necrotic phenotype and the potential to initiate or amplify inflammation. It is engaged in the immune system as a response to defend against pathogenic invasion.
Gasdermins (GSDMs) are a protein family that are considered to be the main executioners of pyroptosis by their ability to form pores in the cell membrane. Especially GSDMD has been thoroughly characterised. Its function is mediated by an N-terminal pore forming domain (PFD) that, in the inactive state, is inhibited by the C‑terminal repressor domain. Upon cleavage by inflammatory Caspases, free PFDs translocate to the membrane and form pores leading to cytokine release, membrane rupture and finally to inflammation of the surrounding tissue.
In contrast to GSDMD, other members of this protein family have not been thoroughly investigated and a variety of questions, regarding expression profiles, molecular mechanism and involvement in RCD, among others, remain unanswered.
Here, we present insights into the structural and functional properties of GSDMX, a hitherto uncharacterised protein, that is a potential novel GSDM family member.
We demonstrate that GSDMX conserves main structures of the GSDM family which are critical for membrane binding and pore forming activity. Furthermore, it was shown that the cleavage of GSDMX is induced by intracellular Ca2+ overload but not by Etoposide treatment. Interestingly, the PFD of GSDMX seems to be able to induce cell death in murine L929 cells but not in human HEK293T cells.
Results presented here support the hypothesis of GSDMX being a hitherto unrecognised member of the GSDM family, but also indicate that it might be activated in a molecular mechanism different to GSDMDs activation. Our results underline the gap of knowledge and understanding of most members of the GSDM family.