Cleavage and Secretion of Interleukin-1b in the Absence of Cell Death. — ASN Events
  1. Schedule
  2. Poster Session 1
  3. Cleavage and Secretion of Interleukin-1b in the Absence of Cell Death.

Cleavage and Secretion of Interleukin-1b in the Absence of Cell Death. (#236)

Stephanie Conos 1 , James Vince 1 , David Vaux 1 , Lisa Lindqvist 1
  1. Walter and Eliza Hall Institute of Medical Research, Melbourne, VIC, Australia

Interleukin-1b (IL-1b) is an important signalling molecule in inflammation and auto-immunity. Specific host, environmental, and pathogen derived danger molecules activate inflammasome protein complexes. These in turn activate caspase-1, which processes IL-1b into its mature biologically active form. Active caspase-1 also induces lytic cell death known as pyroptosis. Whether pyroptosis and IL-1b maturation and secretion are separable events remains unclear.

To study caspase-1 function in the absence of inflammasome signalling we created a lentiviral flag-tagged caspase-1-bacterial DNA-gyrase-GFP fusion construct (FC1GG). Expression of the caspase-1 fusion protein is induced through addition of doxycycline. The dimeric antibiotic coumermycin causes the gyrase domains to dimerise and caspase-1 to auto-activate.

Mouse embryonic fibroblast (MEF) cell lines engineered to constitutively express inactive precursor IL-1b were stably infected with the inducible FC1GG construct. We observed that these cells, which do not express other inflammasome components, secreted IL-1b upon caspase-1 induction and dimerisation. Notably, caspase-1 dependent IL-1b cleavage and secretion occurred in the absence of caspase-1-mediated cell death.

This novel system allows the study of caspase-1-mediated IL-1b secretion without the activation of upstream signalling pathways, or caspase-1 mediated pyroptosis. Consequently, we are currently using it to identify the cellular machinery required for IL-1b secretion via mass-spectrometry based approaches.