Jennifer Luise Hemmings

Design and nuclear magnetic resonance (NMR) structure determination of the second extracellular immunoglobulin tyrosine kinase A (TrkAIg2) domain construct for binding site elucidation in drug discovery

The tyrosine kinase A (TrkA) receptor is a validated therapeutic intervention point for a wide range of conditions. TrkA activation by nerve growth factor (NGF) binding the second extracellular immunoglobulin (TrkAIg2) domain triggers intracellular signaling cascades. In the periphery, this promotes the pain phenotype and, in the brain, cell survival or differentiation. Reproducible structural information and detailed validation of protein–ligand interactions aid drug discovery. However, the isolated TrkAIg2 domain crystallizes as a β-strand-swapped dimer in the absence of NGF, occluding the binding surface. Here we report the design and structural validation by nuclear magnetic resonance spectroscopy of the first stable, biologically active construct of the TrkAIg2 domain for binding site confirmation. Our structure closely mimics the wild-type fold of TrkAIg2 in complex with NGF (1WWW.pdb), and the 1H–15N correlation spectra confirm that both NGF and a competing small molecule interact at the known binding interface in solution.

Molecular Tools for the Cellular Study of Adenosine A1 Receptors

The adenosine receptors are members of the G-protein coupled receptor (GPCR) family which represents the largest class of cell-surface proteins mediating cellular communication. As a result, GPCRs are formidable drug targets and it is estimated that approximately 30% of the marketed drugs act through members of this receptor class. There are four known subtypes of adenosine receptors: A1, A2A, A2B and A3. The adenosine A1 receptor, which is the subject of this presentation, mediates the physiological effects of adenosine in various tissues including the brain, heart, kidney and adipocytes. In the brain for instance, its role in epilepsy and ischemia has been the focus of many studies. Previous attempts to study the biosynthesis, trafficking and agonist-induced internalisation of the adenosine A1 receptor in neurons using fluorescent protein-receptor fusion constructs have been hampered by the sheer size of the fluorescent protein (GFP) that ultimately affected the function of the receptor. We have therefore initiated a research programme to develop small molecule fluorescent agonists that selectively activate the adenosine A1 receptor. Our probe design is based on the endogenous ligand adenosine and the known unselective adenosine receptor agonist NECA. We have synthesised a small library of non-fluorescent adenosine derivatives that have different cyclic and bicyclic moieties at the 6 position of the purine ring and have evaluated the pharmacology of these compounds using a yeast-based assay. This analysis revealed compounds with interesting behaviour, i.e. exhibiting subtype-selectivity and biased signalling, that can be potentially used as tool compounds in their own right for cellular studies of the adenosine A1 receptor. Furthermore, we have also linked fluorescent dyes to the purine ring and discovered fluorescent compounds that can activate the adenosine A1 receptor.

Towards a model of sporadic Alzheimer’s disease: aiding design of small molecule TrkA agonists

It appears that Alzheimer’s disease is a good deal more complete than previously thought and may well have multiple dimensions than just Amyloid Cascade Hypothesis as the only culprit causing the disease. DR. Kokjohn spoke about a more holistic approach taken in the research, where multiple factors are taken into effect in the cause of Alzheimer’s. Tyler explained the difference between Alzheimer’s & Dementia.