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

Dynamin structure and function hinging on Ryngos (#128)

David A Cardoso 1 2 , Mohammed K Abdel-Hamid 3 , Roland Gamsjaeger 4 , Adam McCluskey 3 , Phil J Robinson 1 2
  1. Cell Signalling Unit , Children's Medical Research Institute, Westmead, NSW, Australia
  2. Faculty of Medicine and Health, University of Sydney, Camperdown, NSW, Australia
  3. Faculty of Science, University of Newcastle, Newcastle, NSW, Australia
  4. School of Science and Health, Western Sydney University, Rydalmere, NSW, Australia

Dynamins are multi-domain GTPase enzymes capable of performing the final scission of invaginated plasma membrane prior to the completion of endocytosis. Pharmacological targeting of dynamin in relevant mouse models has been shown to provide therapeutic relief for ailments as diverse as chronic kidney disease and epilepsy. We have generated a series of small molecule modulators (Ryngos) which ‘lock’ dynamin into a ‘ring’ oligomeric state that structurally differs from the ‘helical’ state required for endocytosis. However, these compounds exhibit different activities on enzyme activity in vitro (Ryngo-1: mixed-mode / Ryngo-3: stimulation). Due to their chemical similarity, it can be surmised that these pharmacological agents share a common binding pocket. To establish the binding site of Ryngos and allow for targeted drug design and dissection of dynamin residues responsible for inhibition or stimulation of activity, advanced computer modelling was initially employed. Lead compounds, Ryngo-1-23 and Ryngo-3-32, were predicted to independently localize to, and differentially interact with Hinge 1, located between middle domain and bundle-signalling element of dynamin. A partial overlap of implicated residues between Ryngo-1-23 and Ryngo-3-32 suggests drug binding to different sub-regions of Hinge 1 may be capable of imparting different actions (stimulation/inhibition) on dynamin activity in vitro. To validate this model, mutagenesis of implicated Hinge 1 residues was carried out and resultant mutants characterised. Biochemical assays largely support these predictions (i.e. single mutations specifically lost drug action) as well as highlight a broader role for Hinge 1 in dynamin characteristics (e.g. activity, oligomerisation, and endocytosis). To account for allosteric effects of mutation, a chemically dissimilar dynamin-targeting compound (Dynole-34-2) was employed and revealed loss of Ryngo action to be specific to Hinge 1. The data supports the proposed model of these compounds differentially interacting with a flexible hinge within dynamin, an exceptionally rare binding site for pharmacological agents.