Part:BBa_K2632003

N-terminal of GasderminD (1-275aa)

Pyroptosis is a form of lytic programmed cell death with inflammation. Recent studies reported that the N-terminal of GSDMD acts as an effector of pyroptosis. Full length GSDMD (GSDMD FL) is cleaved by Caspase 1, releasing the pore-forming domain (GSDMD-N275) which can oligomerize and make pores on the cell membrane. Formation of pores causes cell to swell, leading to membrane rupture and massive leakage of cytosolic contents¹.

The N-terminal of GSDMD performs the function of pyroptosis in cells

We fused eGFP with GSDMD-N275 and GSDMD FL (full length), respectively. Then the corresponding plasmids were transfected into Hela GSDMD KO (knockout) cell. Cell microscopy showed that the cells transfected with GSDMD-N275 underwent pyroptosis while the cells with GSDMD FL did not (Figure 1). We also tested the cell viability though an ATP assay (CellTiter-Glo^® Luminescent Cell Viability Assay) and demonstrated that GSDMD-N275 and mutants of GSDMD FL have different ability to induce pyroptosis (Figure 2).

Figure 1. Microscopy of the Hela GSDMD KO cells transfected with pCS2-eGFP-GSDMD FL and pCS2-eGFP-GSDMD-N275, respectively. Pyroptotic cells are pointed by red arrow.

Figure 2. Cell viability of the 293T cells transfected with pCS2-Flag-GSDMD FL, pCS2-Flag-GSDMD-N275, pCS2-Flag-GSDMD L290D, pCS2-Flag-GSDMD Y373D, pCS2-Flag-GSDMD A377D, respectively. Asterisks indicate the statistically significant differences. ATP-based cell viability was measured (n=6).

The N-terminal of GSDMD lyses bacteria

Expression of the N terminal of GSDMD fused with eGFP (eGFP-GSDMD-N275) in Salmonella enterica serovar Typhimurium str. SL1344 ΔsifA is under the control of Ptet. The colony-forming unit (CFU) was measured for counting the number of viable bacteria (Figure 3). The result shows that eGFP-GSDMD-N275 exhibits cytotoxicity to bacteria.

Figure 3. CFU comparison between the SL1344 ΔsifA cells with eGFP-GSDMD-N275 plasmid and with the empty vector. In each group, ATc (15μg/ml) was added into medium when bacteria grew to logarithmic phase (OD = 0.6~0.8). Vector refers to bacteria containing a high copy number plasmid which only expresses TetR under the control of P_tet . Bacterial colony-forming units (CFU) for vector and eGFP-GSDMD-N275 are shown in the logarithmic form (log10) (n = 3).

The N-terminal of GSDMD from lytic bacteria induces cell pyroptosis

Expression of the N-terminal of GSDMD fused with eGFP (eGFP-GSDMD-N275) is under the control of tet promoter in ΔsifA SL1344. Hela GSDMD KO cells were infected with ΔsifA SL1344. Inducer ATc (16μg/mL) was added 3h after infection. Microscopy shows that eGFP-GSDMD-N275 locates in cytoplasm after 5 min of induction and triggers pyroptosis after 30 min of induction (Figure 4). By counting the population of ruptured cells, there is a 1.96 fold-change between the induced group and the control group (Figure 5). So the pyroptosis of host cell in the induced group was triggered by eGFP-GSDMD-N275.

Figure 4. Hela GSDMD KO cells were infected with ΔsifA SL1344 containing high copy number plasmids which express eGFP-GSDMD-N275 under the control of ATc. Photos were captured 5 min, 30min, 1.5h after induction, respectively.

Figure 5. Numbers of pyroptotic cells before and after ATc induction. Ruptured cells in a field of view were counted.

Reference

1. Ding, J. et al. Pore-forming activity and structural autoinhibition of the gasdermin family. Nature 535, 111-116, doi:10.1038/nature18590 (2016).

Sequence and Features

Assembly Compatibility:

• 10
  COMPATIBLE WITH RFC[10]
• 12
  COMPATIBLE WITH RFC[12]
• 21
  COMPATIBLE WITH RFC[21]
• 23
  COMPATIBLE WITH RFC[23]
• 25
  COMPATIBLE WITH RFC[25]
• 1000
  COMPATIBLE WITH RFC[1000]