PhD student profiles

     
     
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Hans Koss
Wellcome Trust 4-year Interdisciplinary PhD Programme, beginning in Autumn 2011

Project title
Studies on solution structure, dynamics and (dys)function of  phospholipase Cg

Principle investigator: Dr Paul C Driscoll, The Francis Crick Institute, Mill Hill Laboratory
Co-investigators: Prof. Matilda Katan, ISMB, UCL and Prof. Peter V Coveney, ISMB, UCL

 
Background
After having studied both medicine (6 year programme) and chemistry (5 year programme) in Berlin and Munich, I graduated from Ludwig Maximilian University in both degrees (Diplom equiv. Master in Chemistry 2010, medical license 2011). I also was awarded a Doctor of Medicine research degree (Dr. med.). My interest in working in interdisciplinary research combined with my affinity for analytical and computational methods led me to join the Wellcome Trust programme in 2012.
 
Rotation projects

Rotation 1
Multiscale molecular modelling of the P2Y11 receptor (Professor Peter V Coveney).

Rotation 2
Peptide-small molecule bioconjugates as inhibitors of VirB11 self-assembly Rotation three (Professor Alethea Tabor)

Rotation 3 (Dr Paul C Driscoll, Professor Matilda Katan)

 
PhD Project

I am studying the solution structure properties and mechanistic features of the phospholipase Cγ (PLCγ), one of the key cell signalling nodes, and its variants that are relevant for human disease. This multidisciplinary project includes aspects of computational biology (molecular dynamics simulations), biophysics (mostly NMR spectroscopy) and molecular biology (generation of protein variants and their expression and purification). A current model for the activation of PLCγ1 by one of upstream regulators, fibroblast growth factor receptor 1 (FGFR1), suggests that phosphorylation of PLCγ1 on Y783 overcomes its auto-inhibited (self-blocking) state. Subsequently, FGFR1 is released from PLCγ1.

In order to investigate how this release is brought about, molecular dynamics simulations were performed to predict potential structural differences between nonphoshorylated and phosphorylated PLCγ1. PLCγ is a multi-domain protein with two SH2 domains in the PLC γ regulatory region involved in activation. The tandem-SH2 protein was analysed to address relative general solution structure differences between nonphospho- and phospho-tandem-SH2 (NMR - chemical shift analysis), relative domain orientation (NMR - residual dipolar coupling), molecular tumbling and dynamics (NMR - relaxation data), and shape (SAXS).

These data form the basis of a new integrative solution structure model of phospho-tandem-SH2. Mechanistic details of how phosphorylation leads to the observed structural change from non-phospho- to phospho-tandem-SH2 and whether this structural changes leads to FGFR1 release are being investigated. These structural and mechanistic studies are important not only for the understanding of PLCγ in health and diseases; there exist many multi-domain proteins that are likely to perform their function based on similar mechanisms. I am demonstrating how it is possible to study those challenging systems and to reveal mechanistic features that would not be accessible using simpler strategies.

animation
Figure 1: Activation of PLCγ1 by tyrosine kinases (here FGFR1) and subsequent release of FGFR1.
 
figure 2
 
Figure 2: Exemplified integrated solution structure models for non-phospho- and phospho-tandem-SH2
 
Activating single point mutations in PLCγ, many discovered only recently, have been linked to immune disease and cancer in humans. This suggests that PLCγ function might be critical for the initiation, persistence or progression of disease. A deeper understanding of how these mutations result in a disease can be gained by elucidating how the mutations modulate PLCγ structure and function. Answering whether some of the mutations have, for example, an impact on FGFR1 release, on phosporylation (activation) rate, on protein stability and/or PLCγ autoinhibition, would have consequences for novel therapeutic approaches for patients with mutations in PLCγ, and also for patients which have other types of cancer or immune disease in which PLCγ plays a role. I am classifying a number of mutations in tandem-SH2 as well as in a protein construct encompassing the PLCγ regulatory region.
 
figure 2
 
Figure 3: Illustration of the structural location of various PLCγ mutations relevant for human disease, adapted from Koss et al., Trends 2014, 39(12). A schematic representation of the spatial organization of PLCγ domains is shown in the upper left corner. Some mutations (red arrows) are located at the autoinhibitory interface, in the cSH2 or in the spPH domain. The location of the mutations in the structural models of the individual domains is shown. The mutation R707Q might disrupt the structure of the cSH2 domain. Other mutations are located at the surface and might, for example, weaken interdomain contacts. CLL = chronic lymphocytic leukaemia; CTCL = cutaneous T-cell lymphoma.
 
Publications

Bunney TD, Wan S, Thiyagarajan N, Sutto L, Williams SV, Ashford P, Koss H, Knowles MA, Gervasio FL, Coveney PV, Katan M. The Effect of Mutations on Drug Sensitivity and Kinase Activity of Fibroblast Growth Factor Receptors: A Combined Experimental and Theoretical Study. EBioMedicine 2015, 2(3).

Koss H, Bunney TD, Behjati S, Katan M. Dysfunction of phospholipase Cγ in immune disorders and cancer. Trends Biochem Sci. 2014, 39(12).

Sayer JR, Walldén K, Pesnot T, Campbell F, Gane PJ, Simone M, Koss H, Buelens F, Boyle TP, Selwood DL, Waksman G, Tabor AB. 2- and 3-substituted imidazo[1,2-a]pyrazines as inhibitors of bacterial type IV secretion. Bioorg. Med. Chem. 2014, 22(22).

Behjati S, Tarpey PS, Sheldon H, Martincorena I, Van Loo P, Gundem G, Wedge DC, Ramakrishna M, Cooke SL, Pillay N, Vollan HK, Papaemmanuil E, Koss H, Katan M, Campbell PJ. Recurrent PTRB and PLCG1 mutations in angiosarcoma. Nature Genetics 2014, 46(4).

Oeckler O, Kechele J, Koss H, Schmidt P, Schnick W. Sr5Al5+xSi21-xN35-xO2+x:Eu2+ (x ≈ 0) - a Novel Green Phosphor for White Light pcLEDs with a Disordered Intergrowth Structure. Chem. Eur. J. 2009, 15(21).

 

 

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