Lightning Talk The 47th Lorne Conference on Protein Structure and Function 2022

Structural and functional analysis of target recognition by the lymphocyte adaptor protein LNK (#25)

Rhiannon Morris 1 2 , Yaoyuan Zhang 3 4 , Julia I Ellyard 3 4 , Carola G Vinuesa 3 4 , James M Murphy 1 2 , Artem Laktyushin 2 , Nadia J Kershaw 1 2 , Jeffrey J Babon 1 2
  1. Department of Medical Biology, The University of Melbourne, Parkville, VIC, Australia
  2. Walter and Eliza Hall Institute, Parkville, VIC, Australia
  3. Centre for Personalised Immunology, John Curtin School of Medical Research, Canberra, ACT, Australia
  4. Department of Immunology and Infectious Diseases, Australian National University, Canberra, ACT, Australia

The SH2B family of adaptor proteins, SH2-B, APS, and LNK are key modulators of intracellular cellular signalling pathways. Each member contains a N-terminal dimerization domain, a central plekstrin homology domain and a C-terminal SH2 domain. The SH2 domain is essential for directing the proteins to their interaction partners, and while the SH2 domains of both APS and SH2B have previously been characterized, the LNK SH2 domain has not. Here we present two crystal structures of the LNK SH2 domain bound to phosphopeptides from JAK2 (1.9 Å) and EPOR (2.3 Å). The LNK SH2 domain adopts a canonical SH2 domain fold with an additional N-terminal helix, and similar to SH2B, but unlike APS, the LNK SH2 domain is monomeric and binds phosphopeptides in an extended linear conformation. Specificity for phosphopeptides is generated by amino acids one- and three-residues downstream of the phosphotyrosine, and analysis of binding to a range of different peptides facilitated identification of several binding sites on other proteins. Further biochemical investigation of three clinically identified SH2 domain mutants in patients with myeloproliferative neoplasms revealed impaired target binding in vitro and a reduced ability to inhibit signalling.  These findings provide insight into phosphotyrosine recognition by its SH2 domain and advance our understanding of the molecular basis of LNK dysfunction in variants identified in patients with myeloproliferative disease.