Poster Presentation The 44th Lorne Conference on Protein Structure and Function 2019

Novel peptide inhibitors of the master stress regulator HSF1 (#265)

Joseph Polidano 1 , Jackie A Wilce 2 , John T Price 1 2 3
  1. Faculty of Medicine Dentistry and Health Sciences (FMDHS), University of Melbourne, Melbourne, Victoria, Australia
  2. Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia
  3. Institute for Health & Sport, Victoria University, Footscray, Victoria, Australia

Heat Shock Factor 1 (HSF1) belongs to a family of highly conserved transcription factor proteins responsible for regulation of the Heat Shock Response (HSR) throughout eukaryotes [1]. The HSR is a survival mechanism undertaken by cells to counter proteotoxic conditions which cause potentially lethal protein damage [2]. HSF1 is the master regulator of this homeostatic response which significantly upregulates several genes, importantly including those which encode for heat shock proteins (HSPs) [2-4].

While central to several pathophysiological conditions, in cancer cells, HSF1 is intimately linked with cancer initiation, progression and metastasis [2, 5, 6]. HSF1 is highly expressed and activated in high grade primary cancers and metastatic lesions, and strongly associated with poor outcomes in cancer patients (lung, breast, prostate, etc) [7-9] .  Its activity is understood to enhance the survival of the cancer cell under stressful conditions [10].

HSF1 has consequently emerged as a major therapeutic target, and this has motivated numerous research groups to undertake programs for the development of HSF1 inhibitors [2, 11, 12]. To date these have been unsuccessful due to an inability to specifically and directly target HSF1 (thus resulting in non-specific modes of action) [2, 11, 12]. We have taken an alternative approach to targeting HSF1, through the development of rationally designed peptide inhibitors.

In this study, we have confirmed that our peptide inhibitor (HiPe4) directly binds HSF1 through use of a biotinylated pulldown of recombinant HSF1. We have also demonstrated that HiPe4 (through incorporation of cell permeability sequences) reduces HSP levels directly regulated by HSF1, while not impacting other proteins not under HSF1 regulation.

To elucidate the binding specificity of HiPe4 for HSF1, we have also generated a suite of HSF homologs and mutant proteins to screen against the peptide mimetics. The outcomes of this work will provide essential data for future binding studies and aid in the development of these first-in-class inhibitors.

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