Oral Presentation The 43rd Lorne Conference on Protein Structure and Function 2018

Assembly and function of two interacting oncogenic pseudokinase scaffolds (#42)

Onisha Patel 1 2 , Michael D.W. Griffin 3 , Santosh Panjikar 4 5 , Weiwen Dai 1 2 , Xiuquan Ma 4 6 , Howard Chan 4 6 , Celine Zheng 1 2 , Ashleigh Kropp 1 2 , James M. Murphy 1 2 , Roger J. Daly 4 6 , Isabelle S. Lucet 1 2
  1. Chemical Biology, The Walter and Eliza Hall Institute of Medical Research, Melbourne, Victoria, Australia
  2. Department of Medical Biology, University of Melbourne, Melbourne, Victoria, Australia
  3. Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Melbourne, Victoria, Australia
  4. Department of Biochemistry and Molecular Biology, Monash University, Melbourne, Victoria, Australia
  5. Australian Synchrotron, Melbourne, Victoria, Australia
  6. Cancer Program, Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, Australia

The mammalian pseudokinase SgK223, and its structurally-related homologue SgK269, are oncogenic scaffolds that nucleate the assembly of specific signaling complexes and regulate tyrosine kinase signalling. Both scaffolds are implicated in specific human malignancies: SgK223 in pancreatic ductal adenocarcinoma (PDAC) progression and SgK269 in colon and breast cancer as well as PDAC. Previously, we demonstrated that these proteins form homo- and hetero-oligomers in vitro and in cells, a mechanism that underpins a diversity of signalling outputs [1]. However, how these two scaffolds organise specific signalling complexes to regulate contrasting cellular responses remains largely uncharacterised.

To gain mechanistic insights into how these enzymatically-dead pseudokinases regulate oncogenic signal transduction networks, we recently determined the structure of SgK223 pseudokinase domain and its adjacent N- and C-terminal helices. Our structure uncovers how the N- and C-regulatory helices engage in a novel fold to mediate the assembly of a high-affinity dimer. In addition, we identified regulatory interfaces on the pseudokinase domain required for the self-assembly of large open-ended oligomers. This study highlights the remarkable diversity in how the kinase fold mediates non-catalytic functions and provides mechanistic insights into how the assembly of these two oncogenic scaffolds is achieved in order to regulate signaling output [2].

  1. [1] Liu L, et al. (2016), Homo- and Heterotypic Association Regulates Signalling by the SgK269/PEAK1 and SgK223 Pseudokinases, J Biol Chem, 291(41):21571-21583. [2] Patel O, et al. (2017), Structure of SgK223 pseudokinase reveals novel mechanism of homotypic and heterotypic association. Nat Commun, DOI: 10.1038/s41467-017-01279-9.