Poster Presentation BACPATH 2022

Drug screening reveals an epigenetic modulator that reduces Salmonella burden in macrophages  (#155)

Jiyao Gan 1 2 , Garrett Z Ng 1 , Sze Ying Ong 1 , Karla J Cowley 3 , Jennii Luu 3 , Kaylene J Simpson 3 4 , Cristina Giogha 1 5 , Elizabeth L Hartland 1 5
  1. Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, Melbourne, Victoria, Australia
  2. Department of Microbiology and Immunology, The University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia
  3. Victorian Centre for Functional Genomics, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
  4. Sir Peter MacCallum Department of oncology and Department of Biochemistry and Pharmacology, University of Melbourne, Melbourne, Victoria, Australia
  5. Department of Molecular and Translational Science, Monash University, Melbourne, Victoria, Australia

Salmonella infects multiple host cell types, including macrophages, to achieve successful colonization of the host. Although replication within macrophages is driven by the bacteria, the intracellular Salmonella niche also offers the potential to target host pathways to prevent infection. In this study, we performed a microscopy-based high-throughput compound screen to identify host cell pathways involved in Salmonella-macrophage interactions. A library of 3088 compounds was used to treat RAW264.7 cells before infection with mCherry-expressing S. Typhimurium. The mCherry signal of intracellular bacteria from each compound treated sample was examined by a confocal microscope. Among these, we identified an epigenetic modulator SGC-CBP30 that reduced S. Typhimurium infection.

 

SGC-CBP30 is a bromodomain inhibitor that targets CREBBP and EP300 (CBP/p300) of host cells. CBP/p300 are transcriptional coactivators with histone acetyltransferase activity that influence multiple signalling pathways. Earlier studies showed that CBP/p300 participates in a wide array of cellular activities such as cell growth, DNA repair, differentiation, and apoptosis. Although the activity of CBP/p300 is relatively well studied in cancer research, its impact on bacterial infection is poorly understood.

 

In our compound screen, SGC-CBP30 reduced Salmonella burden in RAW264.7 cells in a dose-dependent manner. Results of the gentamycin protection assay showed that SGC-CBP30 inhibited bacterial uptake at the early stage of infection, and such inhibition is independent of Salmonella pathogenicity island 1 (SPI-1), suggesting SGC-CBP30 is not targeting the bacterial T3SS for host cell invasion. No cytotoxicity of SGC-CBP30 was observed from our screen and once uptake had occurred, there was no defect in intracellular bacterial replication. Instead, our preliminary data suggested that SGC-CBP30 inhibited the phagocytosis of Salmonella by RAW264.7 cells. The detailed molecular mechanism underlying the reduced bacterial burden in SGC-CBP30 treated RAW264.7 macrophages is being investigated further.